Antibiotic resistance and biofilm formation among coagulase-negative staphylococci isolated from clinical samples at a tertiary care hospital of eastern Nepal

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Abstract

Background

Coagulase negative staphylococci were long regarded non-pathogenic as they are the commensals of human skin and mucosa but the recent changes in the medical practice and changes in underlying host populations, they are being considered significant pathogens associated with number of nosocomial infections. The objective of the study was to determine the species, antimicrobial susceptibility pattern, biofilm forming ability of the clinically significant CoNS isolates and to compare the different methods for the detection of biofilm formation.

Methods

A total of 52 clinically significant CoNS isolates obtained from different units during a year period were studied. Characterization was done using standard microbiological guidelines and antimicrobial susceptibility was done following CLSI guidelines. Biofilm formation was detected by using three methods i.e. tissue culture plate method, congo red agar method and tube adherence method.

Results

Among 52 isolates , S. epidermidis (52%) was the most common species which was followed by S. saprophyticus (18%) and S. haemolyticus (14%). Antimicrobial susceptibility pattern of CoNS documented resistance of 80% to ampicillin. Resistance to cefoxitin and ceftriaxone was observed in 58% of the isolates. Biofilm formation was observed in 65.38% of the isolates. The accuracy of Congo red agar and tube adherence method for the detection of biofilm formation was 82% and 76% respectively.

Conclusion

CoNS isolates obtained from clinical samples should be processed routinely and antimicrobial susceptibility testing should be performed. Multidrug-resistant CoNS are prevalent. All the three methods i.e. tissue culture plate, Congo red agar and tube adherence method can be used in detecting biofilm formation.

Related collections

Most cited references 21

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Adherence of coagulase-negative staphylococci to plastic tissue culture plates: a quantitative model for the adherence of staphylococci to medical devices.

G D Christensen, W A Simpson, J J Younger … (1985)

The adherence of coagulase-negative staphylococci to smooth surfaces was assayed by measuring the optical densities of stained bacterial films adherent to the floors of plastic tissue culture plates. The optical densities correlated with the weight of the adherent bacterial film (r = 0.906; P less than 0.01). The measurements also agreed with visual assessments of bacterial adherence to culture tubes, microtiter plates, and tissue culture plates. Selected clinical strains were passed through a mouse model for foreign body infections and a rat model for catheter-induced endocarditis. The adherence measurements of animal passed strains remained the same as those of the laboratory-maintained parent strain. Spectrophotometric classification of coagulase-negative staphylococci into nonadherent and adherent categories according to these measurements had a sensitivity, specificity, and accuracy of 90.6, 80.8, and 88.4%, respectively. We examined a previously described collection of 127 strains of coagulase-negative staphylococci isolated from an outbreak of intravascular catheter-associated sepsis; strains associated with sepsis were more adherent than blood culture contaminants and cutaneous strains (P less than 0.001). We also examined a collection of 84 strains isolated from pediatric patients with cerebrospinal fluid (CSF) shunts; once again, pathogenic strains were more adherent than were CSF contaminants (P less than 0.01). Finally, we measured the adherence of seven endocarditis strains. As opposed to strains associated with intravascular catheters and CSF shunts, endocarditis strains were less adherent than were saprophytic strains of coagulase-negative staphylococci. The optical densities of bacterial films adherent to plastic tissue culture plates serve as a quantitative model for the study of the adherence of coagulase-negative staphylococci to medical devices, a process which may be important in the pathogenesis of foreign body infections.

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Detection of biofilm formation among the clinical isolates of Staphylococci: an evaluation of three different screening methods.

A. Rattan, Rahul Upadhyay, Khalid Khan … (2005)

The purpose of this study was to evaluate three methods for detection of biofilm formation in staphylococci. For detection of biofilm formation, 152 clinical isolates of Staphylococcus spp. were screened by tissue culture plate (TCP), Tube method (TM) and Congo red agar (CRA) method. Of the 152 Staphylococcus spp. 88(57.8%) displayed a biofilm-positive phenotype under the optimized conditions in the TCP method and strains were further classified as high 22 (14.47 %) and moderate 60 (39.4 %) while in 70 (46.0 %) isolates weak or no biofilm was detected. Though TM correlated well with the TCP test for 18 (11.8 %) strongly biofilm producing strains, weak producers were difficult to discriminate from biofilm negative isolates. Screening on CRA does not correlate well with either of the two methods for detecting biofilm formation in staphylococci. The TCP method was found to be most sensitive, accurate and reproducible screening method for detection of biofilm formation by staphylococci and has the advantage of being a quantitative model to study the adherence of staphylococci on biomedical devices.

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Coagulase-negative staphylococci: pathogens associated with medical progress.

G L Archer, M Rupp (1994)

Coagulase-negative staphylococcal bacteremia and infections of prosthetic medical devices have become major clinical problems. Efforts to differentiate contaminating from infecting isolates consume the time of microbiology laboratory personnel; decisions over when and with what to institute therapy for multiresistant isolates consume the energy of clinicians; and the need to institute expensive parenteral antimicrobial therapy consumes the hospital pharmacy budget. It is clear that the increased incidence of coagulase-negative staphylococcal infections is the result of medical progress and is due to the use of invasive and indwelling medical devices. Multiresistant organisms have evolved that will survive in the presence of antimicrobial agents designed to eradicate more traditional pathogens. They have an ecological niche on human skin from which they are difficult to eradicate, and they have adapted themselves to survive on inert devices designed to persist indefinitely in the human body. Since it is likely that the use of prosthetic medical devices will continue to increase, we need to device innovative strategies for the diagnosis, treatment, and prevention of infections of these indwelling foreign bodies. Studies that will address these issues should be a major goal of future research on hospital-acquired infections.

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Author and article information

Contributors

Lok Bahadur Shrestha: lok.shrestha@bpkihs.edu , drlok86@gmail.com

Narayan Raj Bhattarai: narayan.bhattarai@bpkihs.edu , bhattarai03@gmail.com

Basudha Khanal: basudha.khanal@bpkihs.edu , hod.microbiology@bpkihs.edu , basudhak@gmail.com

Journal

Journal ID (nlm-ta): Antimicrob Resist Infect Control

Journal ID (iso-abbrev): Antimicrob Resist Infect Control

Title: Antimicrobial Resistance and Infection Control

Publisher: BioMed Central (London )

ISSN (Electronic): 2047-2994

Publication date (Electronic): 31 August 2017

Publication date PMC-release: 31 August 2017

Publication date Collection: 2017

Volume: 6

Electronic Location Identifier: 89

Affiliations

ISNI 0000 0004 1794 1501, GRID grid.414128.a, Microbiology & Infectious Diseases, B. P. Koirala Institute of Health Sciences (BPKIHS), ; Dharan, Nepal

Article

Publisher ID: 251

DOI: 10.1186/s13756-017-0251-7

PMC ID: 5579930

PubMed ID: 28883911

SO-VID: beb842e8-80b5-48a3-8b1f-5f8cc0f5bae3

License:

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.