Comparison of Two Disc Diffusion Methods with Minimum Inhibitory Concentration for Antimicrobial Susceptibility Testing of Neisseria Gonorrhoeae Isolates

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Abstract

Background:

A few studies are available comparing either minimum inhibitory concentration (MIC) values with the Clinical and Laboratory Standards Institute (CLSI) disc diffusion method or MIC with the Australian Gonococcal Surveillance Program (AGSP) method.

Aim:

This study was conducted with the aim to identify the most feasible and cost-effective method for antimicrobial susceptibility testing of Neisseria gonorrhoeae.

Materials and Methods:

Antimicrobial susceptibility testing of N. gonorrhoeae was performed using, in parallel, the E-test for MIC determination and disc diffusion by CLSI and AGSP techniques, and were compared. Susceptibility to penicillin, ciprofloxacin, tetracycline, ceftriaxone and spectinomycin and cefixime were determined by CSLI and AGSP method and Kappa statistics used to analyse the data with SPSS software.

Results:

All isolates were susceptible to ceftriaxone and spectinomycin by three methods. Ninety-nine (99%) strains were resistant to ciprofloxacin, while 1% showed intermediate susceptibility to ciprofloxacin by all methods. Statistically, there was a moderate level of agreement between the methods for penicillin.

Conclusion:

All three methods gave reproducible results. Although the media used in the disc diffusion by the AGSP method is easy and cheap to prepare, the CLSI method of disc diffusion testing is recommended for susceptibility testing of gonococcal isolates because of its feasibility and 100% accuracy, with MIC by E-test as the reference method.

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Most cited references 11

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BSAC standardized disc susceptibility testing method (version 8).

, J. E. Andrews (2009)

There have been considerable changes to the format of the recommendations since the previous version (version 7). The majority of the footnotes to the tables have been removed and the notations added to the end column; it is hoped that this change will avoid confusion in interpretation. Antibiotics have been separated into groups, e.g. beta-lactams, aminoglycosides, etc. Recommendations for urinary tract infections (UTIs) have been removed for most agents except for those that are administered solely for the treatment of uncomplicated UTIs or where there are limited recommendations for specific organisms, e.g. trimethoprim. For agents that previously had dual recommendations, systemic recommendations remain and the intermediate category can be used for interpretation for UTIs because intermediate susceptibility infers that the infection may respond as the agent is concentrated at the site of infection. This change will also avoid errors in interpretation when an organism is isolated from multiple sites, e.g. blood and urine. The changes that have been made to version 7 are as follows: MIC and zone diameter breakpoints (BPs) for trimethoprim, fosfomycin and nitrofurantoin for UTIs (Table 7); MIC and zone diameter breakpoints (BPs) for doripenem (Tables 7-9); colistin MIC BPs for Pseudomonas spp. (Table 9), co-trimoxazole MIC BPs for Stenotrophomonas maltophilia (Table 10); staphylococci MIC and zone diameter BPs for clarithromycin, clindamycin, erythromycin, quinupristin/dalfopristin, trimethoprim UTI, nitrofurantoin UTI and rifampicin (Table 11); Streptococcus pneumoniae MIC and zone diameter BPs for azithromycin, clarithromycin, erythromycin, co-trimoxazole, linezolid, rifampicin and telithromycin (Table 12); addition of streptomycin recommendations for enterococci (Table 13); enterococcal MIC and zone diameter BPs for quinupristin/dalfopristin, nitrofurantoin UTI and trimethoprim UTI (Table 13); beta-haemolytic streptococci MIC and zone diameter BPs for azithromycin, clarithromycin, erythromycin and telithromycin (Table 15); clarithromycin and erythromycin MIC and zone diameter BPs for Moraxella catarrhalis (Table 16); azithromycin MIC BPs for Neisseria gonorrhoeae (Table 17); chloramphenicol and rifampicin MIC BPs for Neisseria meningitidis (Table 18); azithromycin MIC BPs for Haemophilus influenzae (Table 19); MIC BPs for metronidazole for Bacteroides fragilis, Bacteroides thetaiotaomicron and Clostridium perfringens (Tables 23-25, respectively); susceptibility testing of Listeria spp. (Appendix 3); the acceptable range for ATCC 25923 to a 10 microg tobramycin disc (Table 26).

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Antimicrobial susceptibilities and plasmid contents of Neisseria gonorrhoeae isolates from commercial sex workers in Dhaka, Bangladesh: emergence of high-level resistance to ciprofloxacin.

N Albert, Shamsun Nahar, Mohammed M. Ahmed … (1999)

Commercial sex workers (CSWs) serve as the most important reservoir of sexually transmitted diseases (STD), including gonorrhea. Periodic monitoring of the antimicrobial susceptibility profile of Neisseria gonorrhoeae in a high-risk population provides essential clues regarding the rapidly changing pattern of antimicrobial susceptibilities. A study concerning the prevalence of gonococcal infection among CSWs was conducted in Bangladesh. The isolates were examined with regards to their antimicrobial susceptibility to, and the MICs of, penicillin, tetracycline, ciprofloxacin, cefuroxime, ceftriaxone, and spectinomycin by disk diffusion and agar dilution methods. The total plasmid profile of the isolates was also analyzed. Of the 224 CSWs, 94 (42%) were culture positive for N. gonorrhoeae. There was a good correlation between the results of the disk diffusion and agar dilution methods. Some 66% of the isolates were resistant to penicillin, and 34% were moderately susceptible to penicillin. Among the resistant isolates, 23.4% were penicillinase-producing N. gonorrhoeae (PPNG). 60.6% of the isolates were resistant and 38.3% were moderately susceptible to tetracycline, 17.5% were tetracycline-resistant N. gonorrhoeae, 11.7% were resistant and 26.6% had reduced susceptibility to ciprofloxacin, 2.1% were resistant and 11.7% had reduced susceptibility to cefuroxime, and 1% were resistant to ceftriaxone. All PPNG isolates contained a 3.2-MDa African type of plasmid, and a 24.2-MDa conjugative plasmid was present in 34.1% of the isolates. Since quinolones such as ciprofloxacin are recommended as the first line of therapy for gonorrhea, the emergence of significant resistance to ciprofloxacin will limit the usefulness of this drug for treatment of gonorrhea in Bangladesh.

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High percentages of resistance to tetracycline and penicillin and reduced susceptibility to azithromycin characterize the majority of strain types of Neisseria gonorrhoeae isolates in Cuba, 1995-1998.

Vinicio Sosa, Yan-Hui Li, Sandra Arcos … (2003)

In many regions the susceptibility of Neisseria gonorrhoeae isolates to antimicrobial agents is rarely tested. The Gonococcal Antimicrobial Surveillance Program (GASP) in Cuba was established as part of a larger regional GASP program to facilitate the collection and reporting of antimicrobial susceptibility data for N gonorrhoeae isolates. The goal was to retrospectively determine the antimicrobial susceptibility and molecular epidemiology of 91 isolates of N gonorrhoeae isolated from 11 centers in Cuba. Isolates of N gonorrhoeae were collected and presumptively identified from 11 Cuban provincial health centers. They were then forwarded to the National Laboratory of Pathogenic Neisseria Havana for confirmatory identification and were subsequently analyzed at the Center for GASP in Ottawa. Isolates were tested for susceptibility to penicillin, tetracycline, spectinomycin, ceftriaxone, ciprofloxacin, and azithromycin by the agar dilution method. To establish baseline data for molecular epidemiologic profiles, the auxotype (A), serovar (S), plasmid content (P), and TetM type of the isolates were determined. Certain A/S/P classes were further analyzed by pulsed field gel electrophoresis (PFGE). High percentages of the 91 N gonorrhoeae isolates were resistant to penicillin (68%) and tetracycline (83.5%), with 56% being penicillinase-producing (PPNG) and 64% carrying plasmid-mediated tetracycline resistance (TRNG; 50% were PP/TRNG). An additional 14% of the isolates carried chromosomal resistance (CMRNG) to either tetracycline or penicillin or both antibiotics. All isolates were susceptible to spectinomycin, ceftriaxone, and ciprofloxacin. However, nine isolates were resistant to azithromycin (MIC, > or = 1.0 microgram/ml), and 43 other isolates displayed reduced susceptibility to this antibiotic (MIC, 0.25-0.5 microgram/ml). Although a total of 21 different A/S classes were identified, most of the isolates (61) belonged to three A/S classes: NR/IA-6 (35 isolates), NR/IB-1 (15 isolates), and P/IA-6 (11 isolates). Thirty-two of 45 PP/TRNG were A/S class NR/IA-6, and nine of the P/IA-6 isolates were TRNG. By contrast, most of A/S class NR/IB-1 (8) were CMRNG. PFGE analysis following digestion with NheI or SpeI further clustered the isolates into separate groups. This study demonstrates high percentages of N gonorrhoeae isolates with penicillin and tetracycline resistance in Cuba. As has been noted in other studies in the Caribbean region and Latin America, resistance and reduced susceptibility to azithromycin are developing as emerging problems. Since penicillin and tetracycline continue to be widely used for the treatment of gonococcal infections in Cuba, this study indicates the importance of antimicrobial susceptibility surveillance so that effective antibiotics may be recommended for treatment of gonococcal infections.

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Author and article information

Journal

Journal ID (nlm-ta): Ann Med Health Sci Res

Journal ID (iso-abbrev): Ann Med Health Sci Res

Journal ID (publisher-id): AMHSR

Title: Annals of Medical and Health Sciences Research

Publisher: Medknow Publications & Media Pvt Ltd (India )

ISSN (Print): 2141-9248

ISSN (Electronic): 2277-9205

Publication date (Print): May-Jun 2014

Volume: 4

Issue: 3

Pages: 453-456

Affiliations

[1] Department of Microbiology, Maulana Azad Medical College, New Delhi, India

Author notes

Address for correspondence: Dr. Preena Bhalla, Department of Microbiology, Maulana Azad Medical College, New Delhi, India. E-mail: preenadr@ 123456gmail.com

Article

Publisher ID: AMHSR-4-453

DOI: 10.4103/2141-9248.133477

PMC ID: 4071750

PubMed ID: 24971225

SO-VID: 258ac4fc-9990-4a1d-9356-697e43bbaa27

License:

This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Comparison of Two Disc Diffusion Methods with Minimum Inhibitory Concentration for Antimicrobial Susceptibility Testing of Neisseria Gonorrhoeae Isolates

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Abstract

Background:

Aim:

Materials and Methods:

Results:

Conclusion:

Related collections

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Most cited references 11

BSAC standardized disc susceptibility testing method (version 8).

Antimicrobial susceptibilities and plasmid contents of Neisseria gonorrhoeae isolates from commercial sex workers in Dhaka, Bangladesh: emergence of high-level resistance to ciprofloxacin.

High percentages of resistance to tetracycline and penicillin and reduced susceptibility to azithromycin characterize the majority of strain types of Neisseria gonorrhoeae isolates in Cuba, 1995-1998.

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