Definition of Terms
Sterilization is the complete elimination or destruction of all forms of microbial
life and is accomplished in health care facilities by either physical or chemical
processes. Steam under pressure, dry heat, ethylene oxide (ETO) gas, hydrogen peroxide
gas plasma, vaporized hydrogen peroxide, and liquid chemicals are the principal sterilizing
agents used in health care facilities. Sterilization is intended to convey an absolute
meaning, not a relative one. Unfortunately, some health care professionals as well
as the technical and commercial literature refer to “disinfection” as “sterilization”
and items as “partially sterile.” When chemicals are used for the purposes of destroying
all forms of microbiologic life, including fungal and bacterial spores, they may be
called chemical sterilants. These same germicides used for shorter exposure periods
may also be part of the disinfection process (i.e., high-level disinfection).
Disinfection describes a process that eliminates many or all pathogenic microorganisms
on inanimate objects, with the exception of bacterial spores. Disinfection is usually
accomplished by the use of liquid chemicals or wet pasteurization in health care settings.
The efficacy of disinfection is affected by a number of factors, each of which may
nullify or limit the efficacy of the process. Some of the factors that affect both
disinfection and sterilization efficacy are the prior cleaning of the object; the
organic and inorganic load present; the type and level of microbial contamination;
the concentration of and exposure time to the germicide; the nature of the object
(e.g., crevices, hinges, and lumens); the presence of biofilms; the temperature and
pH of the disinfection process; and, in some cases, the relative humidity of the sterilization
process (e.g., with ETO).
By definition then, disinfection differs from sterilization by its lack of sporicidal
property, but this is an oversimplification. A few disinfectants will kill spores
with prolonged exposure times (e.g., 3 to 12 hours) and are called chemical sterilants.
At similar concentrations but with shorter exposure periods (e.g., 12 minutes for
0.55% ortho-phthalaldehyde) these same disinfectants will kill all microorganisms
with the exception of large numbers of bacterial spores and are called high-level
disinfectants. Low-level disinfectants may kill most vegetative bacteria, some fungi,
and some viruses in a practical period of time (≤10 minutes), whereas intermediate-level
disinfectants may be cidal for mycobacteria, vegetative bacteria, most viruses, and
most fungi but do not necessarily kill bacterial spores. The germicides differ markedly
among themselves primarily in their antimicrobial spectrum and rapidity of action.
Cleaning, on the other hand, is the removal of visible soil (e.g., organic and inorganic
material) from objects and surfaces, and it normally is accomplished by manual or
mechanical means using water with detergents or enzymatic products. Thorough cleaning
is essential before high-level disinfection and sterilization because inorganic and
organic materials that remain on the surfaces of instruments interfere with the effectiveness
of these processes. Also, if the soiled materials become dried or baked onto the instruments,
the removal process becomes more difficult and the disinfection or sterilization process
less effective or ineffective. Surgical instruments should be presoaked or rinsed
to prevent drying of blood and to soften or remove blood from the instruments. Decontamination
is a procedure that removes pathogenic microorganisms from objects so they are safe
to handle, use, or discard.
Terms with a suffix “-cide” or “-cidal” for killing action also are commonly used.
For example, a germicide is an agent that can kill microorganisms, particularly pathogenic
organisms (“germs”). The term germicide includes both antiseptics and disinfectants.
Antiseptics are germicides applied to living tissue and skin, whereas disinfectants
are antimicrobial agents applied only to inanimate objects. Preservatives are agents
that inhibit the growth of microorganisms capable of causing biologic deterioration
of substances/materials. In general, antiseptics are only used on the skin and not
for surface disinfection and disinfectants are rarely used for skin antisepsis because
they may cause injury to skin and other tissues. Other words with the suffix “-cide”
(e.g., virucide, fungicide, bactericide, sporicide, and tuberculocide) can kill the
type of microorganism identified by the prefix. For example, a bactericide is an agent
that kills bacteria.14, 15, 16, 17, 18, 19
Rational Approach to Disinfection and Sterilization
About 45 years ago, Earle H. Spaulding
15
devised a rational approach to disinfection and sterilization of patient care items
or equipment. This classification scheme is so clear and logical that it has been
retained, refined, and successfully used by infection control professionals and others
when planning methods for disinfection or sterilization.* Spaulding believed that
the nature of disinfection could be understood more readily if instruments and items
for patient care were divided into three categories based on the degree of risk for
infection involved in the use of the items. Although the scheme remains valid, some
examples of disinfection studies with viruses, mycobacteria, and protozoa challenge
the current definitions and expectations of high- and low-level disinfection.
22
The three categories Spaulding described were critical, semicritical, and noncritical.
Critical Items
Critical items are so called because of the high risk for infection if such an item
is contaminated with any microorganism, including bacterial spores. Thus, it is critical
that objects that enter sterile tissue or the vascular system be sterile because any
microbial contamination could result in disease transmission. This category includes
surgical instruments, cardiac and urinary catheters, implants, arthroscopes, laparoscopes,
and ultrasound probes used in sterile body cavities. Most of the items in this category
should be purchased in sterile form or be sterilized by steam sterilization if possible.
If heat sensitive, the object may be treated with ETO, hydrogen peroxide gas plasma,
hydrogen peroxide vapor, or liquid chemical sterilants if other methods are unsuitable.
Tables 301-1
and 301-2
list several germicides categorized as chemical sterilants and high-level disinfectants.
These include 2.4% or greater glutaraldehyde-based formulations, hypochlorous acid/hypochlorite
650 to 675 ppm free chlorine, 1.12% glutaraldehyde with 1.93% phenol/phenate, 3.4%
glutaraldehyde with 26% isopropanol,
23
7.5% stabilized hydrogen peroxide, 2.0% hydrogen peroxide, 7.35% hydrogen peroxide
with 0.23% peracetic acid, 8.3% hydrogen peroxide with 7.0% peracetic acid, 0.2% peracetic
acid, 0.55% or greater ortho-phthalaldehyde, and 0.08% peracetic acid with 1.0% hydrogen
peroxide.
24
Liquid chemical sterilants can be relied on to produce sterility only if cleaning
(to eliminate organic and inorganic material) precedes treatment and if proper use
as to concentration, contact time, temperature, and pH is met.
25
TABLE 301-1
Methods of Sterilization and Disinfection
STERILIZATION
DISINFECTION
Critical Items (will enter tissue or vascular system or blood will flow through them)
High-Level (semicritical items [except dental] will come in contact with mucous membrane
or nonintact skin)
Intermediate-Level (some semicritical items1 and noncritical items)
Low-Level (noncritical items; will come in contact with intact skin)
Object
Procedure
Exposure Time
Procedure (exposure time 12-45 min at ≥20° C2, 3)
Procedure (exposure time ≥1 min9)
Procedure (exposure time ≥1 min9)
Smooth, hard surface1, 4
A
MR
D
A
MR
E
L5
L
C
MR
F
M
M
D
10 hr at 20-25° C
G
N
N
F
6 hr
H
P
O
G
12 min at 50°-56° C
I6
Q
P
J
Q
H
3-8 hr
K
Rubber tubing and catheters3, 4
A
MR
D
B
MR
E
C
MR
F
D
10 hr at 20°-25° C
G
F
6 hr
H
G
12 min at 50°-56° C
I6
H
3-8 hr
J
K
Polyethylene tubing and catheters3, 4, 7
A
MR
D
B
MR
E
C
MR
F
D
10 hr at 20°-25° C
G
F
6 hr
H
G
12 min at 50°-56° C
I6
H
3-8 hr
J
K
Lensed instruments4
A
MR
D
B
MR
E
C
MR
F
D
10 hr at 20°-25° C
G
F
6 hr
H
G
12 min at 50°-56° C
J
H
3-8 hr
K
Thermometers (oral and rectal)8
P8
Hinged instruments4
A
MR
D
B
MR
E
C
MR
F
D
10 hr at 20°-25° C
G
F
6 hr
H
G
12 min at 50°-56° C
I6
H
3-8 hr
J
K
A. Heat sterilization, including steam or hot air (see manufacturer's recommendations,
steam sterilization processing time from 4 to 30 minutes).
B. Ethylene oxide gas (see manufacturer's recommendations, generally 2 to 6 hours
processing time plus aeration time of 8 to 12 hours at 50° to 60° C).
C. Hydrogen peroxide gas plasma (see manufacturer's recommendations for internal diameter
and length restrictions, processing time between 24 to 47 minutes) and vaporized hydrogen
peroxide (see manufacturer's recommendations for internal diameter and length restrictions).
D. Glutaraldehyde-based formulations: ≥2% glutaraldehyde (caution should be exercised
with all glutaraldehyde formulations when further in-use dilution is anticipated);
glutaraldehyde (1.12%) with 1.93% phenol/phenate; and glutaraldehyde (3.4%) with isopropanol
(26%). One glutaraldehyde-based product has a high-level disinfection claim of 5 minutes
at 35° C.
E. Ortho-phthalaldehyde (OPA) 0.55%.
F. Hydrogen peroxide, standard 7.5% (will corrode copper, zinc, and brass).
G. Peracetic acid, concentration variable but ≥0.2% is sporicidal. A 0.2% peracetic
acid immersion reprocessor operates at 50° to 56° C. Per guidance from the FDA, most
hospitals use the 0.2% peracetic acid reprocessor for reprocessing semicritical items
that require high-level disinfection. Thus, as a general rule, the reprocessor will
not be used to reprocess critical items because critical items should be sterile and
with the reprocessor using 0.2% peracetic acid the final processed device cannot be
assured to be sterile. Thus, heat-sensitive critical devices should be sterilized
by other validated, FDA-cleared, sterilization processes such as hydrogen peroxide
gas plasma, ethylene oxide, and vaporized hydrogen peroxide. If a heat-sensitive critical
device truly cannot be processed by any other modality than the reprocessor using
0.2% peracetic acid, then the decision is between not using the device at all or reprocessing
it in the 0.2% peracetic acid reprocessor (at 50° to 56° C). The decision to use the
0.2% peracetic acid reprocessor at 50° to 56° C for a heat-sensitive critical item
that cannot be processed by an alternative sterilization process should be made on
a case-by-case basis.
H. Hydrogen peroxide (7.35%) with 0.23% peracetic acid; hydrogen peroxide 1% with
peracetic acid 0.08%; 8.3% hydrogen peroxide with 7.0% peracetic acid (will corrode
metal instruments).
I. Wet pasteurization at 70°C for 30 minutes with detergent cleaning.
J. Hypochlorite, single-use chlorine generated on site by electrolyzing saline containing
>400 to 675 active free chlorine (will corrode metal instruments).
K. Improved hydrogen peroxide ≥2%.
L. Sodium hypochlorite (5.25% to 6.15% household bleach diluted 1 : 500 provides >100 ppm
available chlorine).
M. Phenolic germicidal detergent solution (follow product label for use-dilution).
N. Iodophor germicidal detergent solution (follow product label for use-dilution).
O. Quaternary ammonium germicidal detergent solution (follow product label for use-dilution).
P. Ethyl and isopropyl alcohol 60% to 95%.
Q. Improved hydrogen peroxide 0.5% and 1.4%.
EPA, U.S. Environmental Protection Agency; FDA, U.S. Food and Drug Administration;
MR, manufacturer's recommendations; NA, not applicable.
Note: The selection and use of disinfectants in the health care field is dynamic,
and products may become available that are not in existence when this chapter was
written. As newer disinfectants become available, persons or committees responsible
for selecting disinfectants and sterilization processes should be guided by products
cleared by the FDA and the EPA as well as by information in the scientific literature
and manufacturer recommendations.
1
See text for discussion of hydrotherapy.
2
The longer the exposure to a disinfectant, the more likely it is that all microorganisms
will be eliminated. Twenty-minute exposure at 20° C is the minimum time needed to
reliably kill Mycobacterium tuberculosis and nontuberculous mycobacteria with 2% glutaraldehyde.
With the exception of >2% glutaraldehyde (see text), follow the FDA-cleared high-level
disinfection claim. Some high-level disinfectants have a reduced exposure time (e.g.,
OPA at 12 minutes at 20° C) because of their rapid activity against mycobacteria or
reduced exposure time due to increased mycobactericidal activity at elevated temperature
(e.g., 2.5% glutaraldehyde at 5 minutes at 35° C, 0.55% OPA at 5 minutes at 25° C
in automated endoscope reprocessor).
3
Tubing must be completely filled for high-level disinfection and liquid chemical sterilization;
care must be taken to avoid entrapment of air bubbles during immersion.
4
Material compatibility should be investigated when appropriate.
5
A concentration of 1000 ppm available chlorine should be considered where cultures
or concentrated preparations of microorganisms have spilled (5.25% to 6.15% household
bleach diluted 1 : 50 provides >1000 ppm available chlorine). This solution may corrode
some surfaces.
6
Pasteurization (washer-disinfector) of respiratory therapy or anesthesia equipment
is a recognized alternative to high-level disinfection. Some data challenge the efficacy
of some pasteurization units.
7
Thermostability should be investigated when appropriate.
8
Do not mix rectal and oral thermometers at any stage of handling or processing.
9
By law, all applicable label instructions on EPA-registered products must be followed.
If the user selects exposure conditions that differ from those on the EPA-registered
products label, the user assumes liability from any injuries resulting from off-label
use and is potentially subject to enforcement action under the Federal Insecticide,
Fungicide, and Rodenticide Act.
Modified from the works of Rutala and Simmons and their colleagues.9, 10, 13, 16,
18, 19, 303
TABLE 301-2
Summary of Advantages and Disadvantages of Chemical Agents Used as Chemical Sterilants
or as High-Level Disinfectants
STERILANT OR DISINFECTANT
ADVANTAGES
DISADVANTAGES
Peracetic acid/hydrogen peroxide
No activation requiredIrritation not significant
Material compatibility concerns (lead, brass, copper, zinc) both cosmetic and functionalLimited
clinical experiencePotential for eye and skin damage
Glutaraldehyde
Numerous use studies publishedRelatively inexpensiveExcellent material compatibility
Respiratory irritation from glutaraldehyde vaporPungent and irritating odorRelatively
slow mycobactericidal activity (unless other disinfectants added such as phenolic,
alcohol)Coagulates blood and fixes tissue to surfacesAllergic contact dermatitis
Hydrogen peroxide, standard
No activation requiredMay enhance removal of organic matter and organismsNo disposal
issuesNo odor or irritation issuesDoes not coagulate blood or fix tissues to surfacesInactivates
Cryptosporidium at high concentrations (e.g., 7.5%)Use studies published
Material compatibility concerns (brass, zinc, copper, and nickel/silver plating) both
cosmetic and functionalSerious eye damage with contactSome studies show limited bactericidal
activity of standard 3%
Ortho-phthalaldehyde
Fast-acting high-level disinfectantNo activation requiredOdor not significantExcellent
materials compatibility claimedEfficacy data publishedDoes not coagulate blood or
fix tissues to surfaces claimed
Stains protein gray (e.g., skin, mucous membranes, clothing, and environmental surfaces)More
expensive than glutaraldehydeEye irritation with contactSlow sporicidal activityContraindicated
for urologic instruments due to anaphylaxis
Peracetic acid
Rapid cycle time (30-45 min)Elevated temperature (50°-55° C) liquid immersionEnvironmental
friendly by-products (acetic acid, O2, H2O)Fully automated endoscope reprocessing
systemSingle-use system eliminates need for concentration testingStandardized cycleMay
enhance removal of organic material and endotoxinNo adverse health effects to operators
under normal operating conditionsCompatible with many materials and instrumentsDoes
not coagulate blood or fix tissues to surfacesSterilant flows through scope facilitating
salt, protein, and microbe removalRapidly sporicidalProvides procedure standardization
(constant dilution, perfusion of channel, temperatures, exposure)
Potential material incompatibility (e.g., aluminum anodized coating becomes dull)Used
for immersible instruments onlyOne scope or a small number of instruments can be processed
in a cycleMore expensive (endoscope repairs, operating costs, purchase costs) than
high-level disinfectionSerious eye and skin damage (concentrated solution) with contactPoint-of-use
system, no long-term storage
Improved hydrogen peroxide (≥2.0%)
No activation requiredNo odorNonstainingNo special venting requirementsManual or automated
applications12-month shelf life, 14-day reuse8 min at 20° C high-level disinfectant
claim
Material compatibility concerns due to limited clinical experienceOrganic material
resistance concerns due to limited dataLimited clinical use and comparative microbicidal
efficacy dataNo measurable activity against Clostridium difficile spores
Note: All products effective in presence of organic soil, relatively easy to use,
and have a broad spectrum of antimicrobial activity (bacteria, fungi, viruses, spores,
and mycobacteria). The above characteristics are documented in the literature; contact
the manufacturer of the instrument and sterilant for additional information.
Modified from references 13, 93, 278, 304.
Semicritical Items
Semicritical items are those that come in contact with mucous membranes or nonintact
skin. Respiratory therapy and anesthesia equipment, some endoscopes, laryngoscope
blades and handles,
26
esophageal manometry probes, endocavitary probes,
26
nasopharyngoscopes, prostate biopsy probes,
27
infrared coagulation device,
28
anorectal manometry catheters, cystoscopes,
29
and diaphragm fitting rings are included in this category.
26
These medical devices should be free of all microorganisms, although small numbers
of bacterial spores may be present. Intact mucous membranes, such as those of the
lungs or the gastrointestinal tract, generally are resistant to infection by common
bacterial spores but susceptible to other organisms such as bacteria, mycobacteria,
and viruses. Semicritical items minimally require high-level disinfection using chemical
disinfectants. Glutaraldehyde, hydrogen peroxide, ortho-phthalaldehyde, peracetic
acid, and peracetic acid with hydrogen peroxide are cleared by the U.S. Food and Drug
Administration (FDA) and are dependable high-level disinfectants provided the factors
influencing germicidal procedures are met (see Tables 301-1 and 301-2). When a disinfectant
is selected for use with certain patient care items, the chemical compatibility after
extended use with the items to be disinfected also must be considered.
The complete elimination of all microorganisms in or on an instrument, with the exception
of small numbers of bacterial spores, is the traditional definition of high-level
disinfection. The FDA's definition of high-level disinfection is a sterilant used
for a shorter contact time to achieve at least a 6-log10 kill of an appropriate Mycobacterium
species. Cleaning followed by high-level disinfection should eliminate sufficient
pathogens to prevent transmission of infection.30, 31
Semicritical items should be rinsed with sterile water after high-level disinfection
to prevent their contamination with organisms that may be present in tap water, such
as nontuberculous mycobacteria,8, 32
Legionella,
33, 34 or gram-negative bacilli such as Pseudomonas.
18, 20, 35, 36, 37 In circumstances where rinsing with sterile water rinse is not
feasible, a tap water or filtered water (0.2-µm filter) rinse should be followed by
an alcohol rinse and forced air drying.9, 37, 38, 39 Forced-air drying markedly reduces
bacterial contamination of stored endoscopes, most likely by removing the wet environment
favorable for bacterial growth.
38
After rinsing, items should be dried and stored (e.g., packaged) in a manner that
protects them from recontamination.
Some items that may come in contact with nonintact skin for a brief period of time
(i.e., hydrotherapy tanks, bed side rails) are usually considered noncritical surfaces
and are disinfected with low- or intermediate-level disinfectants (i.e., phenolic,
iodophor, alcohol, chlorine).
40
Because hydrotherapy tanks have been associated with spread of infection, some facilities
have chosen to disinfect them with recommended levels of chlorine.
40
Noncritical Items
Noncritical items are those that come in contact with intact skin but not mucous membranes.
Intact skin acts as an effective barrier to most microorganisms; therefore, the sterility
of items that come in contact with intact skin is “not critical.” Examples of noncritical
items are bedpans, blood pressure cuffs, crutches, bed rails, bedside tables, patient
furniture, and floors. The five most commonly touched noncritical items in the patient
environment have been quantitatively shown to be bed rails, bed surface, supply cart,
overbed table, and intravenous-line pump.
41
In contrast to critical and some semicritical items, most noncritical reusable items
may be decontaminated where they are used and do not need to be transported to a central
processing area. There is virtually no documented risk of transmitting infectious
agents to patients via noncritical items
36
when they are used as noncritical items and do not contact nonintact skin or mucous
membranes. However, these items (e.g., bedside tables, bed rails) could potentially
contribute to secondary transmission by contaminating hands of health care workers
or by contact with medical equipment that will subsequently come in contact with patients.14,
42, 43, 44, 45
Table 301-1 lists several low-level disinfectants that may be used for noncritical
items. The exposure time listed in Table 301-1 is equal to or greater than 1 minute.
Many U.S. Environmental Protection Agency (EPA)-registered disinfectants have a 10-minute
label claim. However, multiple investigators have demonstrated the effectiveness of
these disinfectants against vegetative bacteria (e.g., Listeria, Escherichia coli,
Salmonella, vancomycin-resistant enterococci [VRE], methicillin-resistant Staphylococcus
aureus [MRSA]), yeasts (e.g., Candida), mycobacteria (e.g., Mycobacterium tuberculosis),
and viruses (e.g., poliovirus) at exposure times of 30 to 60 seconds.42, 43, 44, 45,
46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58 Thus, it is acceptable to disinfect
noncritical medical equipment (e.g., blood pressure cuff) and noncritical surfaces
(e.g., bedside table) with an EPA-registered disinfectant or disinfectant/detergent
at the proper use-dilution and a contact time of at least 1 minute.9, 59 Because the
typical drying time for a germicide on a surface is 1 to 3 minutes (unless the product
contains alcohol [e.g., a 60% to 70% alcohol will dry in about 30 seconds]) (N. Omidbakhsh,
written communication), one application of the germicide on all hand contact surfaces
to be disinfected is recommended.
Mops (microfiber and cotton string), reusable cleaning cloths, and disposable wipes
are regularly used to achieve low-level disinfection.60, 61 Microfiber mops have demonstrated
superior microbial removal compared with cotton string mops when used with detergent
cleaner (95% vs. 68%, respectively). Use of a disinfectant did significantly improve
microbial removal when a cotton string mop was used.
61
Mops (especially cotton-string mops) are commonly not kept adequately cleaned and
disinfected, and if the water-disinfectant mixture is not changed regularly (e.g.,
after every 3 to 4 rooms, no longer than 60-minute intervals), the mopping procedure
may actually spread heavy microbial contamination throughout the health care facility.
62
In one study, standard laundering provided acceptable decontamination of heavily contaminated
mop heads but chemical disinfection with a phenolic was less effective.
62
The frequent laundering of cotton-string mops (e.g., daily) is, therefore, recommended.
Hospital cleanliness continues to attract patient attention and in the United States
it is still primarily assessed via visual appearance, which is not a reliable indicator
of surface cleanliness.
63
Three other methods have been offered for monitoring patient room hygiene and they
include adenosine triphosphate (ATP) bioluminescence,64, 65 fluorescent markers,66,
67 and microbiologic sampling.
65
Studies have demonstrated suboptimal cleaning by aerobic colony counts as well as
the use of the ATP bioluminescence and fluorescent markers.64, 66 ATP bioluminescence
and fluorescent markers are preferred to aerobic plate counts because they provide
an immediate assessment of cleaning effectiveness.
Disinfection of Health Care Equipment and Surfaces
A great number of disinfectants are used alone or in combinations (e.g., hydrogen
peroxide and peracetic acid) in the health care setting. These include alcohols, chlorine
and chlorine compounds, formaldehyde, glutaraldehyde, ortho-phthalaldehyde, standard
and improved hydrogen peroxide, iodophors, peracetic acid, phenolics, and quaternary
ammonium compounds. With some exceptions (e.g., ethanol or bleach), commercial formulations
based on these chemicals are considered unique products and must be registered with
the EPA or cleared by the FDA. In most instances, a given product is designed for
a specific purpose and is to be used in a certain manner. Therefore, the label should
be read carefully to ensure that the right product is selected for the intended use
and applied in an efficient manner. Additionally, caution must be exercised to avoid
hazards with the use of cleaners and disinfectants on electronic medical equipment.
Problems associated with the inappropriate use of liquids on electronic medical equipment
have included equipment fires, equipment malfunctions, and health care worker burns.
68
Disinfectants are not interchangeable and an overview of the performance characteristics
of each is provided in the next section so the user has sufficient information to
select an appropriate disinfectant for any item and use it in the most efficient way.
It should be recognized that excessive costs may be attributed to incorrect concentrations
and inappropriate disinfectants. Finally, occupational diseases among cleaning personnel
have been associated with the use of several disinfectants, such as formaldehyde,
glutaraldehyde, and chlorine, and precautions (e.g., gloves, proper ventilation) should
be used to minimize exposure.
69
Asthma and reactive airway disease may occur in sensitized individuals exposed to
any airborne chemical, including germicides. Clinically important asthma may occur
at levels below ceiling levels regulated by the Occupational and Safety Health Administration
(OSHA) or recommended by the National Institute for Occupational Safety and Health.
The preferred method of control is to eliminate the chemical (via engineering controls,
or substitution) or relocate the worker.
Chemical Disinfectants
Alcohol
In the health care setting, “alcohol” refers to two water-soluble chemical compounds,
the germicidal characteristics of which are generally underrated: ethyl alcohol and
isopropyl alcohol.
70
These alcohols are rapidly bactericidal rather than bacteriostatic against vegetative
forms of bacteria; they also are tuberculocidal, fungicidal, and virucidal but do
not destroy bacterial spores. Their cidal activity drops sharply when diluted below
50% concentration, and the optimal bactericidal concentration is in the range of 60%
to 90% solutions in water (volume/volume).71, 72
Alcohols are not recommended for sterilizing medical and surgical materials, principally
because of their lack of sporicidal action and their inability to penetrate protein-rich
materials. Fatal postoperative wound infections with Clostridium have occurred when
alcohols were used to sterilize surgical instruments contaminated with bacterial spores.
73
Alcohols have been used effectively to disinfect oral and rectal thermometers, computers,
60
hospital pagers, scissors, cardiopulmonary resuscitation (CPR) manikins, applanation
tonometers,
74
external surfaces of equipment (e.g., ventilators), and stethoscopes.
75
Alcohol towelettes have been used for years to disinfect small surfaces such as rubber
stoppers of multiple-dose medication vials or vaccine bottles.
Alcohols are flammable and consequently must be stored in a cool, well-ventilated
area. They also evaporate rapidly, and this makes extended exposure time difficult
to achieve unless the items are immersed.
Chlorine and Chlorine Compounds
Hypochlorites are the most widely used of the chlorine disinfectants and are available
in liquid (e.g., sodium hypochlorite) or solid (e.g., calcium hypochlorite) forms.
The most prevalent chlorine products in the United States are aqueous solutions of
5.25% to 6.15% sodium hypochlorite, which usually are called household bleach. They
have a broad spectrum of antimicrobial activity (i.e., bactericidal, virucidal, fungicidal,
mycobactericidal, sporicidal), do not leave toxic residues, are unaffected by water
hardness, are inexpensive and fast acting,74, 76 remove dried or fixed organisms and
biofilms from surfaces,
77
and have a low incidence of serious toxicity.78, 79 Sodium hypochlorite at the concentration
used in domestic bleach (5.25% to 6.15%) may produce ocular irritation or oropharyngeal,
esophageal, and gastric burns.69, 80, 81 Other disadvantages of hypochlorites include
corrosiveness to metals in high concentrations (>500 ppm), inactivation by organic
matter, discoloring or “bleaching” of fabrics, release of toxic chlorine gas when
mixed with ammonia or acid (e.g., household cleaning agents),
82
and relative stability.
83
Reports have examined the microbicidal activity of a new disinfectant, “superoxidized
water.” The concept of electrolyzing saline to create a disinfectant or antiseptic
is appealing because the basic materials of saline and electricity are inexpensive
and the end product (i.e., water) is not damaging to the environment. The main products
of this “water” are hypochlorous acid (e.g., at a concentration of about 144 mg/L)
and chlorine. This is also known as electrolyzed water; and, as with any germicide,
the antimicrobial activity of superoxidized water is strongly affected by the concentration
of the active ingredient (available free chlorine).
84
The free available chlorine concentrations of different superoxidized solutions reported
in the literature range from 7 to 180 ppm.
84
Data have shown that freshly generated superoxidized water is rapidly effective (<2
minutes) in achieving a 5-log10 reduction of pathogenic microorganisms (i.e., M. tuberculosis,
Mycobacterium chelonae, poliovirus, human immunodeficiency virus (HIV), MRSA, E. coli,
Candida albicans, Enterococcus faecalis, Pseudomonas aeruginosa) in the absence of
organic loading. However, the biocidal activity of this disinfectant was substantially
reduced in the presence of organic material (5% horse serum).85, 86
Hypochlorites are widely used in health care facilities in a variety of settings.
76
Inorganic chlorine solution is used to disinfect tonometer heads
87
and for disinfection of noncritical surfaces and equipment. A 1 : 10 to 1 : 100 dilution
of 5.25% to 6.15% sodium hypochlorite (i.e., household bleach)88, 89, 90, 91 or an
EPA-registered tuberculocidal disinfectant
18
has been recommended for decontaminating blood spills. For small spills of blood (i.e.,
drops of blood) on noncritical surfaces, the area can be disinfected with a 1 : 100
dilution of 5.25% to 6.15% sodium hypochlorite or an EPA-registered tuberculocidal
disinfectant. Because hypochlorites and other germicides are substantially inactivated
in the presence of blood,54, 92 large spills of blood require that the surface be
cleaned before an EPA-registered disinfectant or a 1 : 10 (final concentration) solution
of household bleach is applied. If there is a possibility of a sharps injury, there
should be an initial decontamination,69, 93 followed by cleaning and terminal disinfection
(1 : 10 final concentration).
54
Extreme care should always be used to prevent percutaneous injury. At least 500 ppm
available chlorine for 10 minutes is recommended for decontamination of CPR training
manikins. Other uses in health care include as an irrigating agent in endodontic treatment
and to disinfect laundry, dental appliances, hydrotherapy tanks,
40
regulated medical waste before disposal,
76
applanation tonometers,
74
and the water distribution system in hemodialysis centers and hemodialysis machines.9,
75 Disinfection with a 1 : 10 dilution of concentrated sodium hypochlorite (i.e.,
bleach) has been shown to be effective in reducing environmental contamination in
patient rooms and in reducing C. difficile infection rates in hospital units where
there is a high endemic C. difficile infection rates or in an outbreak setting.9,
94, 95, 96, 97, 98 At our institution, we use a sporicidal solution (5000 ppm chlorine)
in all C. difficile–infected patient rooms for routine daily and terminal cleaning.
This is done by one application of the sporicide covering all hand contact surfaces
to allow sufficient wetness for a greater than 1-minute contact time.
Chlorine has long been favored as the preferred disinfectant in water treatment. Hyperchlorination
of a Legionella-contaminated hospital water system
40
resulted in a dramatic decrease (30% to 1.5%) in the isolation of Legionella pneumophila
from water outlets and a cessation of health care–associated legionnaires' disease
in the affected unit.99, 100 Chloramine T and hypochlorites have been used in disinfecting
hydrotherapy equipment.
75
Hypochlorite solutions in tap water at a pH greater than 8 stored at room temperature
(23° C) in closed, opaque plastic containers may lose up to 40% to 50% of their free
available chlorine level over a period of 1 month. Thus, if a user wished to have
a solution containing 500 ppm of available chlorine at day 30, a solution containing
1000 ppm of chlorine should be prepared at time 0. There is no decomposition of sodium
hypochlorite solution after 30 days when stored in a closed brown bottle.
83
Glutaraldehyde
Glutaraldehyde is a saturated dialdehyde that has gained wide acceptance as a high-level
disinfectant and chemical sterilant.
101
Aqueous solutions of glutaraldehyde are acidic and generally in this state are not
sporicidal. Only when the solution is “activated” (made alkaline) by use of alkalinizing
agents to pH 7.5 to 8.5 does the solution become sporicidal. Once “activated” these
solutions have a shelf life of minimally 14 days because of the polymerization of
the glutaraldehyde molecules at alkaline pH levels. This polymerization blocks the
active sites (aldehyde groups) of the glutaraldehyde molecules that are responsible
for its biocidal activity.
Novel glutaraldehyde formulations (e.g., glutaraldehyde-phenol-sodium phenate, potentiated
acid glutaraldehyde, stabilized alkaline glutaraldehyde) produced in the past 40 years
have overcome the problem of rapid loss of activity (e.g., now use life of 28 to 30
days) while generally maintaining excellent microbicidal activity.74, 75, 102, 103
However, it should be recognized that antimicrobial activity is dependent not only
on age but also on use conditions such as dilution and organic stress. The use of
glutaraldehyde-based solutions in health care facilities is common because of their
advantages, which include excellent biocidal properties; activity in the presence
of organic matter (20% bovine serum); and noncorrosive action to endoscopic equipment,
thermometers, rubber, or plastic equipment. The advantages, disadvantages, and characteristics
of glutaraldehyde are listed in Table 301-2.
The in vitro inactivation of microorganisms by glutaraldehydes has been extensively
investigated and reviewed.
104
Several investigators showed that 2% or greater aqueous solutions of glutaraldehyde,
buffered to pH 7.5 to 8.5 with sodium bicarbonate, were effective in killing vegetative
bacteria in less than 2 minutes; M. tuberculosis, fungi, and viruses in less than
10 minutes; and spores of Bacillus and Clostridium species in 3 hours.
104
Spores of C. difficile are more rapidly killed by 2% glutaraldehyde than are spores
of other species of Clostridium and Bacillus,
105, 106 and this includes the hypervirulent binary toxin strains of C. difficile
spores (W.A. Rutala, unpublished data, December 2012). There have been reports of
microorganisms with relative resistance to glutaraldehyde, including some mycobacteria
(M. chelonae, Mycobacterium avium-intracellulare, Mycobacterium xenopi),107, 108,
109
Methylobacterium mesophilicum,
110
Trichosporon, fungal ascospores (e.g., Microascus cinereus, Chaetomium globosum),
and Cryptosporidium.
111
M. chelonae persisted in a 0.2% glutaraldehyde solution used to store porcine prosthetic
heart valves,
112
and a large outbreak of Mycobacterium massiliense infections in Brazil after videolaparoscopy
equipment used for different elective cosmetic procedures (e.g., liposuction) was
highly tolerant to 2% glutaraldehyde.
113
Porins may have a role in the resistance of mycobacteria to glutaraldehyde and ortho-phthalaldehyde.
114
Dilution of glutaraldehyde during use commonly occurs, and studies show a glutaraldehyde
concentration decline after a few days of use in an automatic endoscope washer.
115
This decline occurs because instruments are not thoroughly dried and water is carried
in with the instrument, which increases the solution's volume and dilutes its effective
concentration. This emphasizes the need to ensure that semicritical equipment is disinfected
with an acceptable concentration of glutaraldehyde. Data suggest that 1.0% to 1.5%
glutaraldehyde is the minimal effective concentration (MEC) for 2% or greater glutaraldehyde
solutions when used as a high-level disinfectant.115, 116, 117 Chemical test strips
or liquid chemical monitors are available for determining whether an effective concentration
of glutaraldehyde is present despite repeated use and dilution. The frequency of testing
should be based on how frequently the solutions are used (e.g., used daily, test daily;
used weekly, test before use), but the strips should not be used to extend the use
life beyond the expiration date. Data suggest the chemicals in the test strip deteriorate
with time,
118
and a manufacturer's expiration date should be placed on the bottles. The bottle of
test strips should be dated when opened and used for the period of time indicated
on the bottle (e.g., 120 days). The results of test strip monitoring should be documented.
The glutaraldehyde test kits have been preliminarily evaluated for accuracy and range,
118
but their reliability has been questioned.
119
The concentration should be considered unacceptable or unsafe when the test indicates
a dilution below the product's MEC (generally to 1.0% to 1.5% glutaraldehyde or lower)
by the indicator not changing color.
Glutaraldehyde is used most commonly as a high-level disinfectant for medical equipment
such as endoscopes,
93
endocavitary probes, spirometry tubing, dialyzers, transducers, anesthesia and respiratory
therapy equipment, hemodialysis proportioning and dialysate delivery systems, and
reuse of laparoscopic disposable plastic trocars.
75
Glutaraldehyde is noncorrosive to metal and does not damage lensed instruments, rubber,
or plastics. The FDA-cleared labels for high-level disinfection with 2% or greater
glutaraldehyde at 25° C range from 20 to 90 minutes depending on the product. However,
multiple scientific studies and professional organizations support the efficacy of
2% or greater glutaraldehyde for 20 minutes at 20° C.9, 18, 37 Minimally, this latter
recommendation should be followed. Glutaraldehyde should not be used for cleaning
noncritical surfaces because it is too toxic and expensive.
Colitis believed to be due to glutaraldehyde exposure from residual disinfecting solution
in the endoscope solution channels has been reported and is preventable by careful
endoscope rinsing.
69
One study found that residual glutaraldehyde levels were higher and more variable
after manual disinfection (<0.2 to 159.5 mg/L) than after automatic disinfection (0.2
to 6.3 mg/L).
120
Similarly, keratopathy and corneal damage were caused by ophthalmic instruments that
were inadequately rinsed after soaking in 2% glutaraldehyde.
121
Glutaraldehyde exposure should be monitored to ensure a safe work environment. In
the absence of an OSHA permissible exposure limit, if the glutaraldehyde level is
higher than the American Conference of Industrial Hygienists ceiling limit of 0.05 ppm,
it would be prudent to take corrective action and repeat monitoring.
122
Hydrogen Peroxide
The literature contains several accounts of the properties, germicidal effectiveness,
and potential uses for stabilized hydrogen peroxide in the health care setting. Published
reports ascribe good germicidal activity to hydrogen peroxide and attest to its bactericidal,
virucidal, sporicidal, and fungicidal properties.123, 124, 125, 126, 127 Some other
studies have shown limited bactericidal and virucidal activity of standard 3% hydrogen
peroxide.58, 74 The advantages, disadvantages, and characteristics of hydrogen peroxide
are listed in Table 301-2. As with other chemical sterilants, dilution of the hydrogen
peroxide must be monitored by regularly testing the MEC (i.e., 7.5 to 6.0%). Compatibility
testing by Olympus America of the 7.5% hydrogen peroxide found both cosmetic changes
(e.g., discoloration of black anodized metal finishes)
93
and functional changes with the tested endoscopes (Olympus, October 15, 1999, written
communication).
Commercially available 3% hydrogen peroxide is a stable and effective disinfectant
when used on inanimate surfaces. It has been used in concentrations from 3% to 6%
for the disinfection of soft contact lenses (e.g., 3% for 2 to 3 hours),123, 128 tonometer
biprisms, ventilators, fabrics,
129
and endoscopes.
130
Hydrogen peroxide was effective in spot-disinfecting fabrics in patients' rooms.
129
Corneal damage from a hydrogen peroxide–soaked tonometer tip that was not properly
rinsed has been reported.
131
Improved Hydrogen Peroxide
An improved hydrogen peroxide–based technology has been introduced into health care
for disinfection of noncritical environmental surfaces and patient equipment
132
and high-level disinfection of semicritical equipment such as endoscopes.133, 134,
135 Improved hydrogen peroxide contains very low levels of anionic or nonionic surfactants
or both in an acidic product that act with hydrogen peroxide to produce microbicidal
activity. This combination of ingredients speeds the antimicrobial activity of hydrogen
peroxide and cleaning efficiency.134, 135 Improved hydrogen peroxide is considered
safe for humans and equipment and benign for the environment. In fact, improved hydrogen
peroxide has the lowest EPA toxicity category (i.e., category IV) based on its oral,
inhalation, and dermal toxicity, which means it is practically nontoxic and not an
irritant.132, 134, 136 It is prepared and marketed by several companies in various
concentrations (e.g., 0.5% to 7%), and different products may use different terminology
for these products, such as “accelerated” or “activated.” Lower concentrations (i.e.,
0.5%,1.4%) are designed for the low-level disinfection of noncritical environmental
surfaces and patient care objects, whereas the higher concentrations can be used as
high-level disinfectants for semicritical medical devices (e.g., endoscopes).
A recent study compared the bactericidal activity of a quaternary ammonium compound
with two new improved hydrogen peroxide products. The improved hydrogen peroxide products
were superior or similar to the quaternary ammonium compound tested. When the two
improved hydrogen peroxide products were compared with standard 0.5%, 1.4%, and 3%
hydrogen peroxide formulations, the improved hydrogen peroxide–based environmental
surface disinfectants proved to be more effective (>6-log10 reduction) and fast-acting
(30-60 seconds) microbicides in the presence of a soil load (to simulate the presence
of body fluids) than commercially available hydrogen peroxide. Only 30- to 60-second
contact time was studied because longer contact times (e.g., 10 minutes) are not achievable
in clinical practice. Additionally, the improved hydrogen peroxide products have an
EPA-registered contact time that is substantially less (e.g., 30 seconds, 1 minute
for bacteria) than most EPA-registered low-level disinfectants.
58
We have also recently shown that the 1.4% activated hydrogen peroxide is very effective
in reducing microbial contamination of hospital privacy curtains. In our study, the
activated hydrogen peroxide completely eliminated contamination with MRSA and VRE
and resulted in a 98.5% reduction in microbes (only Bacillus spp. recoverable). Thus,
at our institution, privacy curtains are being disinfected at the grab area by spraying
the grab area of the curtain three times with activated hydrogen peroxide at discharge
cleaning.
Iodophors
Iodine solutions or tinctures have long been used by health care professionals, primarily
as antiseptics on skin or tissue. The FDA has not cleared any liquid chemical sterilant/high
level disinfectants with iodophors as the main active ingredient. However, iodophors
have been used both as antiseptics and disinfectants. An iodophor is a combination
of iodine and a solubilizing agent or carrier; the resulting complex provides a sustained-release
reservoir of iodine and releases small amounts of free iodine in aqueous solution.
The best known and most widely used iodophor is povidone-iodine, a compound of polyvinylpyrrolidone
with iodine. This product and other iodophors retain the germicidal efficacy of iodine
but, unlike iodine, are generally nonstaining and are relatively free of toxicity
and irritancy.
137
There are several reports that documented intrinsic microbial contamination of antiseptic
formulations of povidone-iodine and poloxamer-iodine.138, 139, 140 It was found that
“free” iodine (I2) contributes to the bactericidal activity of iodophors and dilutions
of iodophors demonstrate more rapid bactericidal action than does a full-strength
povidone-iodine solution. Therefore, iodophors must be diluted according to the manufacturers'
directions to achieve antimicrobial activity.
Published reports on the in vitro antimicrobial efficacy of iodophors demonstrate
that iodophors are bactericidal, mycobactericidal, and virucidal but may require prolonged
contact times to kill certain fungi and bacterial spores.15, 141, 142, 143, 144
Besides their use as an antiseptic, iodophors have been used for the disinfection
of blood culture bottles and medical equipment such as hydrotherapy tanks and thermometers.
Antiseptic iodophors are not suitable for use as hard-surface disinfectants because
of concentration differences. Iodophors formulated as antiseptics contain less free
iodine than those formulated as disinfectants.
145
Iodine or iodine-based antiseptics should not be used on silicone catheters because
the silicone tubing may be adversely affected.
146
Ortho-phthalaldehyde
Ortho-phthalaldehyde (OPA) is a high-level disinfectant that received FDA clearance
in October 1999. It contains at least 0.55% 1,2-benzenedicarboxaldehyde or OPA, and
it has supplanted glutaraldehyde as the most commonly used “aldehyde” for high-level
disinfection in the United States. OPA solution is a clear, pale-blue liquid with
a pH of 7.5. The advantages, disadvantages, and characteristics of OPA are listed
in Table 301-2.
Studies have demonstrated excellent microbicidal activity in in vitro studies,74,
75, 93, 111, 147, 148, 149, 150, 151, 152 including superior mycobactericidal activity
(5-log10 reduction in 5 minutes) compared with glutaraldehyde. Walsh and colleagues
also found OPA effective (>5-log10 reduction) against a wide range of microorganisms,
including glutaraldehyde-resistant mycobacteria and Bacillus atrophaeus spores.
150
OPA has several potential advantages compared with glutaraldehyde. It has excellent
stability over a wide pH range (pH 3 to 9), is not a known irritant to the eyes and
nasal passages, does not require exposure monitoring, has a barely perceptible odor,
and requires no activation. OPA, like glutaraldehyde, has excellent material compatibility.
A potential disadvantage of OPA is that it stains proteins gray (including unprotected
skin) and thus must be handled with caution.
93
However, skin staining would indicate improper handling that requires additional training
and/or personal protective equipment (gloves, eye and mouth protection, fluid-resistant
gowns). OPA residues remaining on inadequately water-rinsed transesophageal echocardiographic
probes may leave stains on the patient's mouth. Meticulous cleaning, use of the correct
OPA exposure time (e.g., 12 minutes), and copious rinsing of the probe with water
should eliminate this problem. Because OPA has been associated with several episodes
of anaphylaxis after cystoscopy,
153
the manufacturer has modified its instructions for use of OPA and contraindicates
the use of OPA as a disinfectant for reprocessing all urologic instrumentation for
patients with a history of bladder cancer. Personal protective equipment should be
worn when handling contaminated instruments, equipment, and chemicals.
148
In addition, equipment must be thoroughly rinsed to prevent discoloration of a patient's
skin or mucous membrane. The MEC of OPA is 0.3%, and that concentration is monitored
by test strips designed specifically for the OPA solution. OPA exposure level monitoring
found that the concentration during the disinfection process was significantly higher
in the manual group (median, 1.43 ppb) than in the automatic group (median, 0.35 ppb).
These findings corroborate other findings that show it is desirable to introduce automatic
endoscope reprocessors to decrease disinfectant exposure levels among scope reprocessing
technicians.
154
Peracetic Acid
Peracetic, or peroxyacetic acid, is characterized by a very rapid action against all
microorganisms. A special advantage of peracetic acid is its lack of harmful decomposition
products (i.e., acetic acid, water, oxygen, hydrogen peroxide); it enhances removal
of organic material
155
and leaves no residue. It remains effective in the presence of organic matter and
is sporicidal even at low temperatures. Peracetic acid can corrode copper, brass,
bronze, plain steel, and galvanized iron, but these effects can be reduced by additives
and pH modifications. The advantages, disadvantages, and characteristics of peracetic
acid are listed in Table 301-2.
Peracetic acid will inactivate gram-positive and gram-negative bacteria, fungi, and
yeasts in less than 5 minutes at less than 100 ppm. In the presence of organic matter,
200 to 500 ppm is required. For viruses the dosage range is wide (12 to 2250 ppm),
with poliovirus inactivated in yeast extract in 15 minutes with 1500 to 2250 ppm.
A processing system using peracetic acid at a temperature of 50° C to 56° C can be
used for processing heat-sensitive semicritical and critical devices that are compatible
with the peracetic acid and processing system and cannot be sterilized by other legally
marketed traditional sterilization methods validated for that type of device (e.g.,
steam, hydrogen peroxide gas plasma, vaporized hydrogen peroxide). After processing,
the devices should be used immediately or stored in a manner similar to that of a
high-level disinfected endoscope.156, 157, 158 The sterilant, 35% peracetic acid,
is diluted to 0.2% with tap water that has been filtered and exposed to ultraviolet
light. Simulated-use trials with the earlier version of this processing system have
demonstrated excellent microbicidal activity,74, 158, 159, 160, 161, 162 and three
clinical trials have demonstrated both excellent microbial killing and no clinical
failures leading to infection.163, 164, 165 Three clusters of infection using the
earlier version of the peracetic acid automated endoscope reprocessor were linked
to inadequately processed bronchoscopes when inappropriate channel connectors were
used with the system.166, 167 These clusters highlight the importance of training,
proper model-specific endoscope connector systems, and quality control procedures
to ensure compliance with endoscope manufacturer's recommendations and professional
organization guidelines. An alternative high-level disinfectant available in the United
Kingdom contains 0.35% peracetic acid. Although this product is rapidly effective
against a broad range of microorganisms,168, 169 it tarnishes the metal of endoscopes
and is unstable, resulting in only a 24-hour use life.
169
Peracetic Acid with Hydrogen Peroxide
Three chemical sterilants are FDA-cleared that contain peracetic acid plus hydrogen
peroxide (0.08% peracetic acid plus 1.0% hydrogen peroxide, 0.23% peracetic acid plus
7.35% hydrogen peroxide, and 8.3% hydrogen peroxide plus 7.0% peracetic acid). The
advantages, disadvantages, and characteristics of peracetic acid with hydrogen peroxide
are listed in Table 301-2.
The bactericidal properties of peracetic acid plus hydrogen peroxide have been demonstrated.
170
Manufacturer's data demonstrated that this combination of peracetic acid plus hydrogen
peroxide inactivated all microorganisms with the exception of bacterial spores within
20 minutes. The 0.08% peracetic acid plus 1.0% hydrogen peroxide product was effective
in inactivating a glutaraldehyde-resistant mycobacteria.
171
The combination of peracetic acid and hydrogen peroxide has been used for disinfecting
hemodialyzers.
172
The percentage of dialysis centers using a peracetic acid with hydrogen peroxide–based
disinfectant for reprocessing dialyzers increased from 5% in 1983 to 72% in 1997.
173
Phenolics
Phenol has occupied a prominent place in the field of hospital disinfection since
its initial use as a germicide by Lister in his pioneering work on antiseptic surgery.
In the past 40 years, however, work has been concentrated on the numerous phenol derivatives
or phenolics and their antimicrobial properties. Phenol derivatives originate when
a functional group (e.g., alkyl, phenyl, benzyl, halogen) replaces one of the hydrogen
atoms on the aromatic ring. Two phenol derivatives commonly found as constituents
of hospital disinfectants are ortho-phenylphenol and ortho-benzyl-para-chlorophenol.
Published reports on the antimicrobial efficacy of commonly used phenolics showed
that they were bactericidal, fungicidal, virucidal, and tuberculocidal.15, 53, 75,
141, 174, 175, 176, 177, 178
Many phenolic germicides are EPA registered as disinfectants for use on environmental
surfaces (e.g., bedside tables, bedrails, laboratory surfaces) and noncritical medical
devices. Phenolics are not FDA cleared as high-level disinfectants for use with semicritical
items but could be used to preclean or decontaminate critical and semicritical devices
before terminal sterilization or high-level disinfection.
The use of phenolics in nurseries has been questioned because of the occurrence of
hyperbilirubinemia in infants placed in bassinets in which phenolic detergents were
used.
179
In addition, Doan and co-workers demonstrated bilirubin level increases in phenolic-exposed
infants compared with nonphenolic-exposed infants when the phenolic was prepared according
to the manufacturers' recommended dilution.
180
If phenolics (or other disinfectants) are used to clean nursery floors, they must
be diluted according to the recommendation on the product label. Phenolics (and other
disinfectants) should not be used to clean infant bassinets and incubators while occupied.
If phenolics are used to terminally clean infant bassinets and incubators, the surfaces
should be rinsed thoroughly with water and dried before the infant bassinets and incubators
are reused.
18
Quaternary Ammonium Compounds
The quaternary ammonium compounds are widely used as surface disinfectants. There
have been some reports of health care–associated infections associated with contaminated
quaternary ammonium compounds used to disinfect patient care supplies or equipment
such as cystoscopes or cardiac catheters.181, 182 As with several other disinfectants
(e.g., phenolics, iodophors), gram-negative bacteria have been found to survive or
grow in them.
140
Results from manufacturers' data sheets and from published scientific literature indicate
that the quaternaries sold as hospital disinfectants are generally fungicidal, bactericidal,
and virucidal against lipophilic (enveloped) viruses; they are not sporicidal and
generally not tuberculocidal or virucidal against hydrophilic (nonenveloped) viruses.†
Poor mycobactericidal activities of quaternary ammonium compounds have been reported.49,
141
The quaternaries are commonly used in ordinary environmental sanitation of noncritical
surfaces such as floors, furniture, and walls. EPA-registered quaternary ammonium
compounds are appropriate to use when disinfecting medical equipment that comes into
contact with intact skin (e.g., blood pressure cuffs).
Pasteurization
Pasteurization is not a sterilization process; its purpose is to destroy all pathogenic
microorganisms with the exception of bacterial spores. The time-temperature relation
for hot-water pasteurization is generally greater than 70° C (158° F) for 30 minutes.
The water temperature and time should be monitored as part of a quality assurance
program.
186
Pasteurization of respiratory therapy187, 188 and anesthesia equipment
189
is a recognized alternative to chemical disinfection.
Ultraviolet Light
Ultraviolet (UV) light has been recognized as an effective method for killing microorganisms.
It has been suggested for use in health care for several purposes, including air disinfection,
room decontamination (see “Room Decontamination,” later), surface disinfection, biofilm
disinfection,
190
and ultrasound probe disinfection.
191
Contaminated ultrasound probes can potentially transmit pathogens. When the probe
is only in contact with the patient's skin there is a low risk for infection and low-level
disinfection is recommended; however, a higher level of disinfection is recommended
when the probe contacts mucous membranes or nonintact skin. An evaluation of a new
disinfection procedure for ultrasound probes using UV light demonstrated the median
microbial reduction for UV light was 100%, 87.5% for antiseptic wiping, and 88% for
dry wiping.
191
Surface disinfection with UV light (100-280 nm) has been evaluated with three hospital-related
surfaces, namely, aluminum (bed railings), stainless steel (operating tables), and
scrubs (laboratory coats). Acinetobacter baumannii were inoculated on small coupons
(103 or 105/coupon) and exposed to 90 J/m2. This exposure was effective in the inactivation
of Acinetobacter from the metal coupon surfaces but ineffective in the decontamination
of scrubs.
192
A hand-held room decontamination technology that utilizes far-UV radiation (185 to
230 nm) to kill pathogens was evaluated and found that it rapidly kills C. difficile
spores and other health care–associated pathogens on surfaces. However, the presence
of organic matter reduces the efficacy of far-UV radiation, possibly explaining the
more modest results observed on surfaces in hospital rooms that were not precleaned.
193
Sterilization
Most medical and surgical devices used in health care facilities are made of materials
that are heat stable and thus are sterilized by heat, primarily steam sterilization.
However, since 1950, there has been an increase in medical devices and instruments
made of materials (e.g., plastics) that require low-temperature sterilization. ETO
has been used since the 1950s for heat- and moisture-sensitive medical devices. Within
the past 15 years, a number of new, low-temperature sterilization systems (e.g., hydrogen
peroxide gas plasma, vaporized hydrogen peroxide) have been developed and are being
used to sterilize medical devices. This section reviews sterilization technologies
used in health care and makes recommendations for their optimum performance in the
processing of medical devices.9, 194
Sterilization destroys all microorganisms on the surface of an object or in a fluid
to prevent disease transmission associated with the use of that item. Although the
use of inadequately sterilized critical items represents a high risk for transmitting
pathogens, documented transmission of pathogens associated with an inadequately sterilized
critical item is exceedingly rare.195, 196, 197 This is likely due to the wide margin
of safety associated with the sterilization processes used in health care facilities.
The concept of what constitutes “sterile” is measured as a probability of sterility
for each item to be sterilized. This probability is commonly referred to as the sterility
assurance level (SAL) of the product and is defined as the probability of a single
viable microorganism occurring on a product after sterilization. SAL is normally expressed
as 10−n. For example, if the probability of a spore surviving were one in 1 million,
the SAL would be 10−6.198, 199 Dual SALs (e.g., 10−3 SAL for blood culture tubes,
drainage bags; 10−6 SAL for scalpels, implants) have been used in the United States
for many years, and the choice of a 10−6 SAL was strictly arbitrary and not associated
with any adverse outcomes (e.g., patient infections).
198
Medical devices that have contact with sterile body tissues or fluids are considered
critical items. These items should be sterile when used because any microbial contamination
could result in disease transmission. Such items include surgical instruments, biopsy
forceps, and implanted medical devices. If these items are heat resistant, the recommended
sterilization process is steam sterilization, because it has the largest margin of
safety due to its reliability, consistency, lethality, and least effect from organic/inorganic
soils. However, reprocessing heat- and moisture-sensitive items requires use of a
low-temperature sterilization technology (e.g., ETO, hydrogen peroxide gas plasma,
vaporized hydrogen peroxide).
200
A summary of the advantages and disadvantages for commonly used sterilization technologies
is presented in Table 301-3
.
TABLE 301-3
Summary of Advantages and Disadvantages of Commonly Used Sterilization Technologies
STERILIZATION METHOD
ADVANTAGES
DISADVANTAGES
Steam
Nontoxic to patient, staff, environmentCycle easy to control and monitorRapidly microbicidalLeast
affected by organic/inorganic soils among sterilization processes listedRapid cycle
timePenetrates medical packing, device lumens
Deleterious for heat-sensitive instrumentsMicrosurgical instruments damaged by repeated
exposureMay leave instruments wet, causing them to rustPotential for burns
Hydrogen peroxide gas plasma
Safe for the environmentLeaves no toxic residualsCycle time is ≥24 min and no aeration
necessaryUsed for heat- and moisture-sensitive items since process temperature <50° CSimple
to operate, install (208-V outlet), and monitorCompatible with most medical devicesOnly
requires electrical outlet
Cellulose (paper), linens, and liquids cannot be processed.Endoscope or medical device
restrictions based on lumen internal diameter and length (see manufacturer's recommendations)Requires
synthetic packaging (polypropylene wraps, polyolefin pouches) and special container
trayHydrogen peroxide may be toxic at levels greater than 1 ppm TWA.
100% Ethylene oxide (ETO)
Penetrates packaging materials, device lumensSingle-dose cartridge and negative-pressure
chamber minimizes the potential for gas leak and ETO exposureSimple to operate and
monitorCompatible with most medical materials
Requires aeration time to remove ETO residueETO is toxic, a carcinogen, and flammable.ETO
emission regulated by states but catalytic cell removes 99.9% of ETO and converts
it to CO2 and H2O.ETO cartridges should be stored in flammable liquid storage cabinet.Lengthy
cycle/aeration time
ETO mixtures: 8.6% ETO/91.4% HCFC 10% ETO/90% HCFC 8.5% ETO/91.5% CO2
Penetrates medical packaging and many plasticsCompatible with most medical materialsCycle
easy to control and monitor
Some states (e.g., CA, NY, MI) require ETO emission reduction of 90%-99.9%.CFC (inert
gas that eliminates explosion hazard) banned in 1995Potential hazards to staff and
patientsLengthy cycle/aeration timeETO is toxic, a carcinogen, and flammable.ETO mixtures
to be phased out by end of 2014
Vaporized hydrogen peroxide
Safe for the environment and health care workerLeaves no toxic residue; no aeration
necessaryFast cycle time: 55 minUsed for heat and moisture sensitive items (metal
and nonmetal devices)
Medical devices restrictions based on lumen internal diameter and length; see manufacturer's
recommendations (e.g., stainless steel lumen 1-mm diameter, 125-mm length)Not used
for liquid, linens, powders, or any cellulose materialsRequires synthetic packaging
(polypropylene)Limited materials compatibility dataLimited clinical use and comparative
microbicidal efficacy data
CFC, chlorofluorocarbon; HCFC, hydrochlorofluorocarbon; TWA, time-weighted average.
Modified from references 13, 200, 278.
Steam Sterilization
Of all the methods available for sterilization, moist heat in the form of saturated
steam under pressure is the most widely used and the most dependable. Steam sterilization
is nontoxic, inexpensive,
201
rapidly microbicidal, and sporicidal and rapidly heats and penetrates fabrics (see
Table 301-3).
202
Like all sterilization processes, steam sterilization has some deleterious effects
on some materials, including corrosion and combustion of lubricants associated with
dental handpieces,
203
reduction in ability to transmit light associated with laryngoscopes,
204
and increased hardening time (fivefold to sixfold) with plaster cast.
205
The basic principle of steam sterilization, as accomplished in an autoclave, is to
expose each item to direct steam contact at the required temperature and pressure
for the specified time. Thus, there are four parameters of steam sterilization: steam,
pressure, temperature, and time. The ideal steam for sterilization is dry saturated
steam and entrained water (dryness fraction ≥97%).
194
Pressure serves as a means to obtain the high temperatures necessary to quickly kill
microorganisms. Specific temperatures must be obtained to ensure the microbicidal
activity. The two common steam sterilizing temperatures are 121° C (250° F) and 132° C
(270° F). These temperatures (and other high temperatures) must be maintained for
a minimal time to kill microorganisms. Recognized minimum exposure periods for sterilization
of wrapped health care supplies are 30 minutes at 121° C in a gravity displacement
sterilizer or 4 minutes at 132° C in a prevacuum sterilizer. At constant temperatures,
sterilization times vary depending on the type of item (e.g., metal versus rubber,
plastic, items with lumens), whether the item is wrapped or unwrapped, and the sterilizer
type.
The two basic types of steam sterilizers (autoclaves) are the gravity displacement
autoclave and the high-speed prevacuum sterilizer. In the former, steam is admitted
at the top or the sides of the sterilizing chamber and, because the steam is lighter
than air, forces air out the bottom of the chamber through the drain vent. The gravity
displacement autoclaves are primarily used to process laboratory media, water, pharmaceutical
products, regulated medical waste, and nonporous articles whose surfaces have direct
steam contact. With gravity displacement sterilizers the penetration time into porous
items is prolonged because of incomplete air elimination. The high-speed prevacuum
sterilizers are similar to the gravity displacement sterilizers except they are fitted
with a vacuum pump (or ejector) to ensure air removal from the sterilizing chamber
and load before the steam is admitted. The advantage of a vacuum pump is that there
is nearly instantaneous steam penetration even into porous loads.
Like other sterilization systems, the steam cycle is monitored by physical, chemical,
and biological monitors. Steam sterilizers usually are monitored using a printout
(or graphically) by measuring temperature, the time at the temperature, and pressure.
Typically, chemical indicators are affixed to the outside and incorporated into the
pack to monitor the temperature or time and temperature. The effectiveness of steam
sterilization is monitored with a biological indicator containing spores of Geobacillus
stearothermophilus (formerly Bacillus stearothermophilus). Positive spore test results
are a relatively rare event and can be attributed to operator error, inadequate steam
delivery,
206
or equipment malfunction.
Portable steam sterilizers are used in outpatient, dental, and rural clinics. These
sterilizers are designed for small instruments, such as hypodermic syringes and needles
and dental instruments. The ability of the sterilizer to reach physical parameters
necessary to achieve sterilization should be monitored by physical, chemical, and
biologic indicators.
Steam sterilization should be used whenever possible on all critical and semicritical
items that are heat and moisture resistant (e.g., steam sterilizable respiratory therapy
and anesthesia equipment), even when not essential to prevent pathogen transmission.
Steam sterilizers also are used in health care facilities to decontaminate microbiologic
waste and sharps containers,
207
but additional exposure time is required in the gravity displacement sterilizer for
these items.
Immediate-Use Steam Sterilization
“Flash” steam sterilization was originally defined by Underwood and Perkins as sterilization
of an unwrapped object at 132° C for 3 minutes at 27 to 28 pounds of pressure in a
gravity displacement sterilizer.
208
It was intended for instruments (e.g., dropped instruments) when there is insufficient
time to sterilize an item by the preferred package method. The term “flash” arose
out of the abbreviated time of exposure of the unwrapped instrument. Flash sterilization
is an antiquated term that does not fully describe the various steam sterilization
cycles now used to process items not intended to be stored for later use. Immediate
use is defined as the shortest possible time between a sterilized item's removal from
the sterilizer and its aseptic transfer to the sterile field. This implies that the
sterilized item is used during the procedure for which it was sterilized and in a
manner that minimizes its exposure to air and other environmental contaminants. The
same critical reprocessing steps (e.g., cleaning, decontamination, rinsing, and aseptic
transfer from the sterilizer to the point of use) must be followed. Immediate-use
steam sterilization should not be used for convenience, as an alternative to purchasing
sufficient instrument sets, or as a time saver.209, 210
Ethylene Oxide “Gas” Sterilization
ETO is a colorless gas that is flammable and explosive. The four essential parameters
(operational ranges) are gas concentration (450 to 1200 mg/L); temperature (37° C
to 63° C); relative humidity (40% to 80%; water molecules carry ETO to reactive sites);
and exposure time (1 to 6 hours). These parameters influence the effectiveness of
ETO sterilization.211, 212, 213, 214 Within certain limitations, an increase in gas
concentration and temperature may shorten the time necessary for achieving sterilization.
The main disadvantages associated with ETO are the lengthy cycle time and its potential
hazards to patients and staff; the main advantages are that it is highly penetrating
and can sterilize occluded locations in medical items and can sterilize heat- or moisture-sensitive
medical equipment without deleterious effects on the material used in the medical
devices (see Table 301-3).
212
Acute exposure to ETO may result in irritation (e.g., to skin, eyes, or gastrointestinal
or respiratory tracts) and central nervous system depression.
69
Chronic inhalation has been linked to the formation of cataracts, cognitive impairment,
neurologic dysfunction, and disabling polyneuropathies.
69
Occupational exposure in health care facilities has been linked to hematologic changes
and an increased risk for spontaneous abortions and various cancers.
69
ETO should be considered a known human carcinogen.
215
The use of ETO evolved when few alternatives existed for sterilizing heat- and moisture-sensitive
medical devices; however, favorable properties (see Table 301-3) account for its continued
widespread use.
216
Two ETO gas mixtures are available to replace ETO-chlorofluorocarbon (CFC) mixtures
for large capacity, tank-supplied sterilizers. The ETO-carbon dioxide (CO2) mixture
consists of 8.5% ETO and 91.5% CO2. This mixture has limited use in U.S. health care
facilities but is sometimes used in hospitals in India and China. It is less expensive
than ETO-hydrochlorofluorocarbons (HCFC), but a disadvantage is the need for pressure
vessels rated for steam sterilization, because higher pressures (28-psi gauge) are
required. The other mixture, which is a drop-in CFC replacement, is ETO mixed with
HCFC. HCFCs are approximately 50-fold less damaging to the earth's ozone layer than
are CFCs. The EPA will begin regulation of HCFC in the year 2015 and will terminate
production in the year 2030. The ETO-HCFC mixtures have been provided by companies
as a drop-in replacement for CFC-12 (one mixture consists of 8.6% ETO and 91.4% HCFC,
and the other mixture is composed of 10% ETO and 90% HCFC) but will be phased out
by the end of 2013.
216
An alternative to the pressurized mixed-gas ETO systems is 100% ETO. Partly because
of the events just described, the 100% ETO sterilizers that use unit-dose cartridges
will become the systems for ETO use in U.S. health care facilities.
The excellent microbicidal activity of ETO has been demonstrated in several studies25,
161, 162, 217, 218, 219 and summarized in published reports.
220
ETO inactivates all microorganisms, although bacterial spores (especially B. atrophaeus)
are more resistant than other microorganisms. For this reason, B. atrophaeus is the
recommended biologic indicator organism.
Like all sterilization processes, the effectiveness of ETO sterilization can be altered
by lumen length, lumen diameter, inorganic salts, and organic materials.‡ For example,
although ETO is not used commonly for reprocessing endoscopes,
39
several studies have shown failure of ETO in inactivating contaminating spores in
endoscope channels
221
or lumen test units.25, 161, 218 Residual ETO levels averaging 66.2 ppm have been
found even after the standard degassing time.
130
Failure of ETO also has been observed when dental handpieces were contaminated with
Streptococcus mutans and exposed to ETO.
222
It is recommended that dental handpieces be steam sterilized.
ETO is used in health care facilities to sterilize critical items (and sometimes semicritical
items) that are moisture or heat sensitive and cannot be sterilized by steam sterilization.
Hydrogen Peroxide Gas Plasma
New sterilization technology based on hydrogen peroxide and plasma was patented in
1987 and marketed in the United States in 1993. Gas plasmas have been referred to
as the fourth state of matter (i.e., liquids, solids, gases, and gas plasmas). Gas
plasmas are generated in an enclosed chamber under deep vacuum using radiofrequency
or microwave energy to excite the gas (i.e., hydrogen peroxide) molecules and produce
charged particles, many of which are in the form of free radicals (e.g., hydroxyl
and hydroperoxyl). This system works by diffusing hydrogen peroxide into the chamber
and then “exciting” the hydrogen peroxide into a plasma state. The combined use of
hydrogen peroxide vapor and plasma safely and rapidly sterilizes instruments without
leaving toxic residues. The biologic indicator used with this system is Geobacillus
stearothermophilus spores.
This process has the ability to inactivate a broad range of microorganisms, including
resistant bacterial spores. Studies have been conducted against vegetative bacteria
(including mycobacteria), yeasts, fungi, viruses, and bacterial spores.25, 161, 219,
223, 224, 225, 226, 227, 228, 229 Like all sterilization processes, the effectiveness
can be altered by lumen length, lumen diameter, inorganic salts, and organic materials.§
Materials and devices that cannot tolerate high temperatures and humidity, such as
some plastics, electrical devices, and corrosion-susceptible metal alloys, can be
sterilized by hydrogen peroxide gas plasma. This method has been compatible with most
(>95%) medical devices and materials tested.230, 231
Vaporized Hydrogen Peroxide
A new low temperature sterilization system uses vaporized hydrogen peroxide to sterilize
reusable metal and nonmetal devices used in health care facilities. The system is
compatible with a wide range of medical instruments and materials (e.g., polypropylene,
brass, polyethylene). There are no toxic by-products because only water vapor and
oxygen are produced. The system is not intended to process liquids, linens, powders,
or any cellulose materials. The system can sterilize instruments with diffusion-restricted
spaces (e.g., scissors) and medical devices with a single stainless steel lumen based
on lumen internal diameter and length (e.g., an inside diameter of 1 mm or larger
and a length of 125 mm or shorter; see manufacturer's recommendations). Thus, gastrointestinal
endoscopes and bronchoscopes cannot be sterilized in this system at the current time.
Although this system has not been comparatively evaluated with other sterilization
processes, vaporized hydrogen peroxide has been shown to be effective in killing spores,
viruses, mycobacteria, fungi, and bacteria. Table 301-3 lists the advantages and disadvantages
of this and other processes.
Disinfection
Reprocessing of Endoscopes
Physicians use endoscopes to diagnose and treat numerous medical disorders. Although
endoscopes represent a valuable diagnostic and therapeutic tool in modern medicine
and the incidence of infection associated with use has been reported as very low (about
1 in 1.8 million procedures),
232
more health care–associated outbreaks have been linked to contaminated endoscopes
than to any other medical device.4, 5, 6, 233 To prevent the spread of health care–associated
infections, all heat-sensitive endoscopes (e.g., gastrointestinal endoscopes, bronchoscopes,
nasopharyngoscopes) must be properly cleaned and at a minimum subjected to high-level
disinfection after each use. High-level disinfection can be expected to destroy all
microorganisms; although when high numbers of bacterial spores are present, a few
spores may survive.
Recommendations for the cleaning and disinfection of endoscopic equipment have been
published and should be strictly followed.9, 37, 234, 235 Unfortunately, audits have
shown that personnel do not adhere to guidelines on reprocessing,236, 237, 238, 239
and outbreaks of infection continue to occur.240, 241 To ensure that reprocessing
personnel are properly trained, there should be initial and annual competency testing
for each individual who is involved in reprocessing endoscopic instruments.9, 38,
167, 234
In general, endoscope disinfection or sterilization with a liquid chemical sterilant
or high-level disinfectant involves five steps after leak testing:
1.
Clean—mechanically clean internal and external surfaces, including brushing internal
channels and flushing each internal channel with water and a enzymatic cleaner.
2.
Disinfect—immerse endoscope in high-level disinfectant (or chemical sterilant) and
perfuse (eliminates air pockets and ensures contact of the germicide with the internal
channels) disinfectant into all accessible channels such as the suction/biopsy channel
and air/water channel and expose for a time recommended for specific products.
3.
Rinse—rinse the endoscope and all channels with sterile water, filtered water (commonly
used with automated endoscope reprocessors), or tap water.
4.
Dry—rinse the insertion tube and inner channels with alcohol and dry with forced air
after disinfection and before storage.
5.
Store—store the endoscope in a way that prevents recontamination and promotes drying
(e.g., hung vertically).
Unfortunately, there is poor compliance with the recommendations for reprocessing
endoscopes, which may result in patient exposure to bloodborne pathogens.
242
In addition, there are rare instances in which the scientific literature and recommendations
from professional organizations regarding the use of disinfectants and sterilants
may differ from the manufacturer's label claim. One example is the contact time used
to achieve high-level disinfection with 2% glutaraldehyde. Based on FDA requirements
(FDA regulates liquid sterilants and high-level disinfectants used on critical and
semicritical medical devices), manufacturers test the efficacy of their germicide
formulations under worst-case conditions (i.e., minimum recommended concentration
of the active ingredient) and in the presence of organic soil (typically 5% serum).
The soil is used to represent the organic loading to which the device is exposed during
actual use and that would remain on the device in the absence of cleaning. These stringent
test conditions are designed to provide a margin of safety by ensuring that the contact
conditions for the germicide provide complete elimination of the test bacteria (e.g.,
105 to 106
M. tuberculosis in organic soil and dried on a scope) if inoculated into the most
difficult areas for the disinfectant to penetrate and in the absence of cleaning.
However, the scientific data demonstrate that M. tuberculosis levels can be reduced
by at least 8 log10 with cleaning (4 log10) followed by chemical disinfection for
20 minutes at 20° C (4 to 6 log10).9, 37, 243 Because of these data, professional
organizations (at least 14 professional organizations worldwide) that have endorsed
an endoscope reprocessing guideline recommend contact conditions of 20 minutes at
20° C (or <20 minutes outside the United States) with 2% glutaraldehyde to achieve
high-level disinfection that differs from that of the manufacturer's label.37, 244,
245, 246 It is important to emphasize that the FDA tests do not include cleaning,
a critical component of the disinfection process. Therefore, when cleaning has been
included in the test methodology, 2% glutaraldehyde for 20 minutes has been demonstrated
to be effective in eliminating all vegetative bacteria.
OSHA Bloodborne Pathogen Standard
In December 1991 OSHA promulgated a standard entitled “Occupational Exposure to Bloodborne
Pathogens” to eliminate or minimize occupational exposure to bloodborne pathogens.
247
One component of this requirement is that all equipment and environmental and working
surfaces be cleaned and decontaminated with an appropriate disinfectant after contact
with blood or other potentially infectious materials. Although the OSHA standard does
not specify the type of disinfectant or procedure, the OSHA original compliance document
248
suggested that a germicide must be tuberculocidal to kill hepatitis B virus (e.g.,
phenolic, chlorine). However, in February 1997, OSHA amended its policy and stated
that EPA-registered disinfectants that are labeled as effective against HIV and hepatitis
B virus would be considered as appropriate disinfectants “provided such surfaces have
not become contaminated with agent(s) or volumes of or concentrations of agent(s)
for which higher level disinfection is recommended.” When bloodborne pathogens other
than hepatitis B virus or HIV are of concern, OSHA continues to require the use of
EPA-registered tuberculocidal disinfectants or hypochlorite solution (diluted 1 : 10
or 1 : 100 with water).89, 249 Recent studies demonstrate that, in the presence of
large blood spills, a 1 : 10 final dilution of EPA-registered hypochlorite solution
initially should be used to inactivate bloodborne viruses54, 250 to minimize risk
for disease to the health care worker from percutaneous injury during the clean-up
process.
Emerging Pathogens, Antibiotic-Resistant Bacteria, and Bioterrorism Agents
Emerging pathogens are of growing concern to the general public and infection control
professionals. Relevant pathogens include Cryptosporidium parvum, C. difficile, severe
acute respiratory syndrome (SARS)-coronavirus, Helicobacter pylori, E. coli O157:H7,
HIV, hepatitis C virus (HCV), rotavirus, multidrug-resistant M. tuberculosis, human
papillomavirus, norovirus, and nontuberculous mycobacteria (e.g., M. chelonae). Similarly,
publications have highlighted the concern about the potential for bioterrorism.
251
The Centers for Disease Control and Prevention (CDC) has categorized several agents
as “high priority” because they can be easily disseminated or transmitted person to
person, can cause high mortality, and are likely to cause public panic and social
disruption.
252
These agents include Bacillus anthracis (anthrax), Yersinia pestis (plague), variola
major (smallpox), Francisella tularensis (tularemia), filoviruses (Ebola hemorrhagic
fever, Marburg hemorrhagic fever); and arenaviruses (Lassa [Lassa fever], Junin [Argentine
hemorrhagic fever]), and related viruses.
252
With rare exceptions, the susceptibility of each of these pathogens to chemical disinfectants/sterilants
has been studied and all of these pathogens (or surrogate microbes such as feline-calicivirus
for norovirus, vaccinia for variola,
142
and B. atrophaeus [formerly Bacillus subtilis] for B. anthracis), are susceptible
to currently available chemical disinfectants/sterilants.9, 253, 254 Standard sterilization
and high-level disinfection procedures for patient care equipment (as recommended
in this chapter) are adequate to sterilize or disinfect instruments or devices contaminated
with blood or other body fluids from persons infected with bloodborne pathogens, emerging
pathogens, and bioterrorism agents, with the exception of prions (see later). No changes
in procedures for cleaning, disinfecting, or sterilizing need to be made.
9
In addition, there are no data to show that antibiotic-resistant bacteria (methicillin-resistant
Staphylococcus aureus [MRSA], vancomycin-resistant Enterococcus [VRE], multidrug-resistant
M. tuberculosis) are less sensitive to the liquid chemical germicides that antibiotic-sensitive
bacteria at currently used germicide contact conditions and concentrations.255, 256
Current Issues in Disinfection and Sterilization
Inactivation of Creutzfeldt-Jakob Disease Agent
Creutzfeldt-Jakob disease (CJD) is a degenerative neurologic disorder of humans with
an incidence in the United States of approximately 1 case/million population/year.257,
258 CJD is believed to be caused by a proteinaceous infectious agent or prion. CJD
is related to other human transmissible spongiform encephalopathies (TSEs) that include
kuru (0 incidence, now eradicated), Gertsmann-Straussler-Sheinker (GSS) syndrome (1/40
million), and fatal insomnia syndrome (FFI) (<1/40 million). The agents of CJD and
other TSEs exhibit an unusual resistance to conventional chemical and physical decontamination
methods. Because the CJD agent is not readily inactivated by conventional disinfection
and sterilization procedures and because of the invariably fatal outcome of CJD, the
procedures for disinfection and sterilization of the CJD prion have been both conservative
and controversial for many years.
The current recommendations consider inactivation data but also use epidemiologic
studies of prion transmission, infectivity of human tissues, and the efficacy of removing
proteins by cleaning.257, 259, 260 On the basis of scientific data, only critical
(e.g., surgical instruments) and semicritical devices contaminated with high-risk
tissue (i.e., brain, spinal cord, and eye tissue) from high-risk patients (e.g., known
or suspected infection with CJD or other prion disease) require special prion reprocessing.
A moist environment after contamination reduces the attachment of both protein and
prion amyloid to the stainless steel surface so moist conditions should be maintained.
261
After the device is clean, it should be sterilized by either autoclaving (i.e., steam
sterilization) or using a combination of sodium hydroxide and autoclaving
262
using one of the options below
257
:
Option 1—autoclave at 134° C for 18 minutes in a prevacuum sterilizer
Option 2—autoclave at 132° C for 1 hour in a gravity displacement sterilizer9, 257,
263
Option 3—immerse in 1N sodium hydroxide for 1 hour; remove and rinse in water, then
transfer to an open pan and autoclave (121° C gravity displacement or 134°C porous
or prevacuum sterilizer) for 1 hour
Option 4—immerse in 1N sodium hydroxide for 1 hour and heat in a gravity displacement
at 121° C for 30 minutes, then clean and subject to routine sterilization.
Some data suggest the temperature should not exceed 134° C because the effectiveness
of autoclaving may decline as the temperature is increased (e.g., 136° C, 138° C).
264
Prion-contaminated medical devices that are impossible or difficult to clean should
be discarded. To minimize environmental contamination, noncritical environmental surfaces
should be covered with plastic-backed paper; and when contaminated with high-risk
tissues, the paper should be properly discarded. Noncritical environmental surfaces
(e.g., laboratory surfaces) contaminated with high-risk tissues should be cleaned
and then spot decontaminated with a 1 : 10 dilution of hypochlorite solutions.
257
Role of Surfaces in Disease Transmission
There is excellent evidence in the scientific literature that environmental contamination
plays an important role in the transmission of several key health care–associated
pathogens, including MRSA, VRE, Acinetobacter, norovirus, and C. difficile.
265, 266, 267, 268 All these pathogens have been demonstrated to persist in the environment
for days (in some cases months), frequently contaminate the environmental surfaces
in rooms of colonized or infected patients, transiently colonize the hands of health
care personnel, be transmitted by health care personnel, and cause outbreaks in which
environmental transmission was deemed to play a role. Importantly, a recent study
by Steifel and associates demonstrated that contact with the environment was just
as likely to contaminate the hands of health care workers as was direct contact with
the patient.
269
Further, admission to a room in which the previous patient was colonized or infected
with MRSA, VRE, Acinetobacter, or C. difficile has been shown to be a risk factor
for the newly admitted patient to develop colonization or infection.270, 271
Adequacy of Room Cleaning and Disinfection Using Chemical Germicides
It has long been recommended in the United States that environmental surfaces in patient
rooms be cleaned and disinfected on a regular basis (e.g., daily or three times per
week), when surfaces are visibly soiled, and after patient discharge (terminal cleaning).
9
Disinfection is generally performed using an EPA-registered hospital disinfectant
such as a quaternary ammonium compound. Recent studies have demonstrated that adequate
environment cleaning is frequently lacking. For example, Carling and co-workers assessed
the thoroughness of terminal cleaning in the patient's immediate environment in 23
acute care hospitals (1119 patient rooms) by using a transparent, easily cleaned,
stable solution that fluoresces when exposed to hand-held UV light.
272
The overall thoroughness of cleaning, expressed as a percent of surfaces evaluated,
was 49% (range for all hospitals, 35% to 81%). Using a similar design, Carling and
co-workers assessed the environmental cleaning in intensive care unit rooms in 16
hospitals (2320 objects) and demonstrated that only 57.1% of sites were cleaned after
discharge of the room's occupant.
273
A recent study using ATP bioluminescence assays and aerobic cultures demonstrated
that medical equipment frequently had not been disinfected as per protocol.
274
Improving Room Cleaning and Disinfection and Demonstrating the Effectiveness of Surface
Decontamination in Reducing Health Care–Associated Infections
Investigators have reported that intervention programs aimed at environmental services
workers resulted in significant improvement in cleaning practices.65, 66 Such interventions
have generally included multiple activities: improved education, monitoring the thoroughness
of cleaning (e.g., by use of ATP assays or fluorescent dyes) with feedback of performance
to the environmental service workers or use of cleaning checklists or both. We have
found that assignment of cleaning responsibility (e.g., medical equipment to be cleaned
by nursing; environmental surfaces to be cleaned by environmental service) is also
important to ensure all objects and surfaces are decontaminated, especially the surfaces
of medical equipment (e.g., cardiac monitors). Improved environmental cleaning has
been demonstrated to reduce the environmental contamination with VRE,275, 276 MRSA,
276
and C. difficile.
277
Importantly, no study has reported in the postintervention period proper cleaning
of more than 85% of objects. Further, all studies have only focused improvement on
a limited number of “high risk” objects. Thus, a concern of published studies is that
they have only demonstrated improved cleaning of a limited number of “high risk” objects
(or “targeted” objects), not an improvement in the overall thoroughness of room decontamination.
“No Touch” Methods for Room Decontamination
As noted earlier, multiple studies have demonstrated that environmental surfaces and
objects in rooms are frequently not properly cleaned and these surfaces may be important
in transmission of health care–associated pathogens. Further, although interventions
aimed at improving cleaning thoroughness have demonstrated effectiveness, many surfaces
remain inadequately cleaned and therefore potentially contaminated. For this reason,
several manufacturers have developed room disinfection units that can decontaminate
environmental surfaces and objects. These systems use one of two methods—either ultraviolet
light or hydrogen peroxide.
268
These technologies supplement, but do not replace, standard cleaning and disinfection
because surfaces must be physically cleaned of dirt and debris.
Ultraviolet Light for Room Decontamination
UV irradiation has been used for the control of pathogenic microorganisms in a variety
of applications, such as control of legionellosis, as well as disinfection of air,
surfaces, and instruments.278, 279 At certain wavelengths, UV light will break the
molecular bonds in DNA, thereby destroying the organism. UV-C has a characteristic
wavelength of 200 to 270 nm (e.g., 254 nm), which lies in the germicidal active portion
of the electromagnetic spectrum of 200 to 320 nm. The efficacy of UV irradiation is
a function of many different parameters such as intensity, exposure time, lamp placement,
and air movement patterns.
An automated mobile UV-C unit has been shown to eliminate more than 3-log10 vegetative
bacteria (MRSA, VRE, Acinetobacter baumannii) and more than 2.4-log10
C. difficile seeded onto Formica surfaces in patients' rooms experimentally contaminated.
280
Boyce and colleagues report the results of assessing the effectiveness of the same
UV-C unit to reduce environmental contamination with vegetative bacteria (measured
using aerobic colony counts) and C. difficile inoculated onto stainless steel carrier
disks.
281
Room decontamination with the UV system resulted in significant reductions in aerobic
bacteria on five high-touch surfaces. Mean C. difficile log10 reductions ranged from
1.8 to 2.9 using cycle times of 34.2 to 100.1 minutes. Surfaces in direct line-of-sight
were significantly more likely to yield negative cultures after UV decontamination
than before decontamination. Nerandzic and colleagues showed that UV-C at a reflected
dose of 22,000 mWs/cm2 for approximately 45 minutes consistently reduced recovery
of C. difficile spores and MRSA by more than 2- to 3-log10 colony-forming units (CFU)/cm2
and of VRE by more than 3- to 4-log10 CFU/cm2.
282
Thus, there are now three studies that have demonstrated that a UV-C system is capable
of reducing vegetative bacteria inoculated on a carrier by more than 3- to 4-log10
in 15 to 20 minutes and C. difficile by more than 1.7- to 4-log10 in 35 to 100 minutes.
The studies also demonstrate reduced effectiveness when surfaces were not in direct
line of sight.280, 281, 282
Hydrogen Peroxide Systems for Room Decontamination
Several systems that produce hydrogen peroxide (e.g., vapor, aerosolized dry mist)
have been studied for their ability to decontaminate environmental surfaces and objects
in hospital rooms. Hydrogen peroxide vapor (HPV) has been used increasingly for the
decontamination of rooms in health care facilities.283, 284, 285, 286, 287, 288, 289,
290, 291, 292 Investigators found that hydrogen peroxide systems are a highly effective
method for eradicating various pathogens (e.g., MRSA, M. tuberculosis, Serratia, C.
difficile spores, Clostridium botulinum spores) from rooms, furniture, and equipment.
Importantly, using a before-after study design, Boyce and co-workers have shown that
use of hydrogen peroxide vapor was associated with a significant reduction in the
incidence of C. difficile infection on five high-incidence wards.
283
Comparison of Ultraviolet Irradiation versus Hydrogen Peroxide for Room Decontamination
The UV-C system studied and the systems that use hydrogen peroxide have their own
advantages and disadvantages
268
and there is now ample evidence that these “no-touch” systems can reduce environmental
contamination with health care–associated pathogens. However, each specific system
should be studied and its efficacy demonstrated before being introduced into health
care facilities. The main advantage of both units is their ability to achieve substantial
reductions in vegetative bacteria. As noted earlier, manual cleaning has been demonstrated
to be suboptimal because many environmental surfaces are not cleaned. Another advantage
is their ability to substantially reduce C. difficile because low-level disinfectants
(e.g., quaternary ammonium compounds) have limited or no measurable activity against
spore-forming bacteria.
278
Both systems are residual free and they decontaminate all exposed surfaces and equipment
in the room.
The major disadvantages of both decontamination systems are the substantial capital
equipment costs, the need to remove personnel and patients from the room, thus limiting
their use to terminal room disinfection (must prevent/minimize exposure to UV and
hydrogen peroxide), the staff time needed to transport the system to rooms to be decontaminated
and monitor its use, the need to physically clean the room of dust and debris, and
the sensitivity to use parameters. There are several important differences between
the two systems. The UV-C system offers faster decontamination that reduces the “down”
time of the room before another patient can be admitted. The hydrogen peroxide systems
have been demonstrated to be more effective in eliminating spore-forming organisms.
Whether this improved sporicidal activity is clinically important is unclear because
studies have demonstrated that although environmental contamination is common in the
rooms of patients with C. difficile infection, the level of contamination is relatively
low (also true for MRSA and VRE). Finally, the hydrogen peroxide system was demonstrated
to reduce C. difficile incidence in a clinical study, whereas similar studies with
the UV-C system have not been published. If additional studies continue to demonstrate
a benefit, then widespread adoption of these technologies should be considered for
terminal room disinfection of certain patient rooms (e.g., contact precautions) in
health care facilities.
Control of Hospital Waste
Health care facilities that generate medical, chemical, or radiologic waste have a
moral and legal obligation to dispose of these wastes in a manner that poses minimal
potential hazard to the environment or public health. The proper disposal of these
wastes requires a dynamic waste management plan that conforms to federal, state, and
local regulations and provides adequate personnel and financial resources to ensure
implementation.
Medical waste disposal has been as a major problem in the United States for the past
40 years. The problem has developed as a result of medical waste washing ashore in
some coastal states in 1987 and 1988 and the perceived threat of acquiring HIV infection
via this waste. This has led to restrictive rules governing the disposal of medical
waste in many states and an increase in the volume of waste defined as regulated medical
waste. Coincidentally, with an increase in volume of regulated medical waste (formerly
called “infectious waste”), the options for medical waste treatment and disposal are
diminishing because of space and environmental concerns. This section will review
some of the principles associated with medical waste management, but a more detailed
description of collection, storage, processing, transporting, treatment, and public
health implications of medical waste may be found elsewhere.293, 294, 295, 296, 297
Despite the attention given to medical waste by the public, the media, and all levels
of government, the terms hospital waste, medical waste, regulated medical waste, and
infectious waste are often used synonymously. Hospital waste refers to all waste,
biologic or nonbiologic, that is discarded and not intended for further use. Medical
waste refers to materials generated as a result of patient diagnosis, immunization,
or treatment, such as soiled dressings or intravenous tubing. Infectious waste refers
to that portion of medical waste that could potentially transmit an infectious disease.
Congress and the EPA used the term regulated medical waste rather than infectious
waste in the Medical Waste Tracking Act (MWTA) of 1988 in deference to the remote
possibility of disease transmission associated with this waste. Thus, medical waste
is a subset of hospital waste, and regulated medical waste (which is synonymous with
infectious waste from a regulatory perspective) is a subset of medical waste.
293
As stated, regulated medical waste (or infectious waste) is capable of producing an
infectious disease. This definition requires a consideration of the factors necessary
for disease induction that include dose, host susceptibility, presence of a pathogen,
virulence of a pathogen, and the most commonly absent factor, a portal of entry. For
a waste to be infectious, therefore, it must contain pathogens with sufficient virulence
and quantity so that exposure to the waste by a susceptible host could result in an
infectious disease. Because there are no tests that allow infectious waste to be identified
objectively, responsible agencies (e.g., the CDC, EPA, or states) define waste as
infectious when it is suspected to contain pathogens in sufficient number to cause
disease. Not only does this subjective definition result in conflicting opinions from
the CDC, EPA, and state agencies on what constitutes infectious waste and how it should
be treated, but it also gives undue emphasis to the mere presence of pathogens.
Guidelines produced by the CDC have designated five types of hospital waste as regulated
medical waste (i.e., microbiology laboratory waste, pathology and anatomy waste, contaminated
animal carcasses, blood, and sharps).
40
The EPA guidelines consider the same types of waste as infectious or regulated medical
waste but also designate communicable disease isolation waste.
296
In the MWTA, the EPA modified its position on “communicable disease isolation waste”
by including only certain “highly” communicable disease waste such as Class 4 (e.g.,
Marburg, Ebola, and Lassa viruses) as regulated medical waste
298
(Table 301-4
). In a systematic random survey of all U.S. hospitals conducted in July 1987 and
January 1988, the overall compliance rates with the CDC and EPA recommendations were
82% and 75%, respectively. Not only were the majority of hospitals in compliance,
but the hospitals frequently treated other hospital waste as infectious, including
contaminated laboratory waste (87%), surgery waste (78%), dialysis waste (69%), items
contacting secretions (63%), intensive care (37%), and emergency department waste
(41%).
293
TABLE 301-4
Types of Medical Waste Designated as Infectious (or Regulated Medical Waste) and Recommended
Disposal/Treatment Methods: CDC and EPA
SOURCE/TYPE OF MEDICAL WASTE
CDC
EPA
MWTA
Infectious Waste Methods
Disposal/Treatment
Infectious Waste Methods
Disposal/Treatment
Infectious Waste*
Microbiologic (e.g., stocks and cultures of infectious agents)
Yes†
S, I
Yes
S, I, TI, C
Yes
Blood and blood products
Yes
S, I, Sew
Yes
S, I, Sew, C
Yes
Pathologic (e.g., tissue, organs)
Yes
I
Yes
I, SW, CB
Yes
Sharps (e.g., needles)
Yes
S, I
Yes
S, I
Yes‡
Communicable disease isolation
No
—
Yes
S, I
Yes‡
Contaminated animal carcasses, body parts, and bedding
Yes
S, I (carcasses)
Yes
I, SW (not bedding)
Yes
Contaminated laboratory wastes
No
—
Optional§
If considered IW, use S or I
No
Surgery and autopsy wastes
No
—
Optional
If considered IW, use S or I
No
Dialysis Unit
No
—
Optional
If considered IW, use S or I
No
Contaminated equipment
No
—
Optional
If considered IW, use Sor I
No
CDC, Centers for Disease Control and Prevention
40
; EPA, U.S. Environmental Protection Agency
296
; MWTA, Medical Waste Tracking Act.
298
Disposal/Treatment abbreviations: C, chemical disinfection for liquids only; CB, cremation
or burial by mortician; I, incineration; IW, infectious waste; S, steam sterilization;
Sew, sanitary sewer (EPA requires secondary treatment); SW, steam sterilization with
incineration or grinding; TI, thermal inactivation.
Note: The Joint Commission requires that there be a hazardous waste system designed
and operated in accordance with applicable law and regulations.
*
The CDC guidelines specify “microbiology laboratory waste” as infectious waste. This
term includes stocks and cultures of etiologic agents and microbiology laboratory
waste contaminated with etiologic agents (e.g., centrifuge tubes, pipettes, tissue
culture bottles).
†
The Act went into effect on June 22, 1989, and expired June 22, 1991. It affected
only four states (New Jersey, New York, Connecticut, and Rhode Island). The Act required
both treatment (any method, technique, or process designed to change the biologic
character or composition of medical waste so as to eliminate or reduce its potential
for causing disease) and destruction (waste is ruined, torn apart, or mutilated so
that it is no longer generally recognizable as medical waste).
‡
MWTA specified used and unused sharps. The Act regulated wastes from persons with
highly communicable diseases such as Class 4 etiologic agents (e.g., Marburg, Ebola,
Lassa viruses).
§
Optional infectious waste: EPA states that the decision to handle these wastes as
infectious should be made by a responsible, authorized person or committee at the
individual facility.
Modified from Rutala WA, Mayhall CG; Society of Hospital Epidemiology of America.
Position paper: Medical waste. Infect Control Hosp Epidemiol. 1992:13;38-48.
A key component in evaluating the impact of a medical waste management program is
the quantity of waste produced per patient. Hospitalized patients generate about 15
pounds of hospital waste per day. The amount of hospital waste generated by U.S. hospitals
is approximately 6700 tons per day. U.S. hospitals designate approximately 15% of
the total hospital waste by weight as infectious (about 1000 tons of infectious waste
per day).
293
Not surprisingly, the percentage of medical waste treated as infectious increases
with the number and types of medical waste classified as infectious. For example,
about 6% of hospital waste would be treated as infectious waste if the CDC guidelines
are followed but 45% of hospital waste could be considered infectious waste under
the MWTA.293, 299
The vast majority of U.S. hospitals designate and treat microbiologic, pathologic,
isolation, blood, and sharp waste as infectious.
293
In the late 1980s, treatment of infectious waste by U.S. hospitals was most commonly
accomplished by incineration (range, 64% to 93%, depending on the type of waste),
but emission regulations that limit air pollutants has reduced the number and use
of incineration for medical waste. For example, in September 1997 there were an estimated
2373 medical waste incinerators in the United States, but based on the EPA's 2010
inventory there are 54 infectious waste incinerators.
300
Autoclaves or steam sterilizers have become the primary nonincineration technology
used by hospitals to process their regulated medical waste (except pathology waste)
(E. Krisiunas, written communication, 2008). Several other nonincineration alternatives
have been proposed for treating regulated medical waste (e.g., mechanical/chemical
disinfection, microwave decontamination, steam disinfection, and compacting).
297
Nonregulated medical waste is generally discarded in a properly sited and operated
sanitary landfill because this is a safe and inexpensive disposal method (e.g., landfill
disposal costs $0.02 to 0.05 per pound for nonregulated medical waste versus a contract
incinerator cost of $0.20 to 0.60 per pound for regulated medical waste).
The conflicting opinions of state and federal regulations are related to the paucity
of microbiologic and epidemiologic evidence that medical waste represents a threat
to the public health. First, with the exception of “sharps” such as needles, which
have caused disease only in an occupational setting, there is no scientific evidence
that medical waste has caused disease in the hospital or the community. Second, data
demonstrate that household waste contains on average 100 times as many microorganisms
with pathogenic potential for humans than medical waste.
301
Third, detailed reports of the beach washups found that the vast majority of waste
on beaches was debris (about 99%) such as wood, plastic, and paper, not medical waste.
EPA documents acknowledge that much of the medical waste that washed ashore in the
summer of 1988 was syringe related (65%) and came from home health care and illegal
drug use. Fourth, studies have shown that most U.S. hospitals are in compliance with
the CDC infectious waste guidelines. Fifth, although the principal purpose of the
MWTA was to reduce medical waste on beaches, it has not demonstrated its intended
benefit. The relative number of syringes on the beaches in the MWTA states was significantly
greater during implementation of the Act (17.23%) than before the Act went into effect
(3.2%).
299
If regulatory control were based on epidemiologic, microbiologic, and environmental
data, only two types of medical waste would require special handling and treatment—sharps
and microbiologic waste.
Federal medical waste regulations have been promulgated by the U.S. Department of
Transportation and OSHA. The Department of Transportation regulation involves the
transport of infectious substances and medical waste and went into effect January
1996.
302
The OSHA Bloodborne Pathogen Standard requires labeling to designate waste that poses
a health threat in the workplace. The OSHA definition of regulated waste is not intended
to designate waste that must be treated. In fact, generators who apply the OSHA definition
of regulated waste (rather than state regulations) to designate infectious waste for
treatment by incineration or other means may unintentionally incur additional expenses.
247
Conclusion
When properly used, disinfection and sterilization can ensure the safe use of invasive
and noninvasive medical devices. However, current disinfection and sterilization guidelines
must be strictly followed.