COMPARISON OF ETEST AND AGAR DILUTION FOR DETERMINING MINIMUM INHIBITORY CONCENTRATION OF VANCOMYCIN TO HEALTHCARE-ASSOCIATED METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
Abstract
ABSTRACT
Objectives: To compare agar dilution method and Etest in the determination of minimum inhibitory concentration (MIC) of vancomycin to healthcareassociated
methicillin-resistant
Staphylococcus
aureus
(HA-MRSA).
Methods: A total of 98 non-duplicate strains of HA-MRSA isolated from different clinical specimens were tested for their antibiotic susceptibility
pattern by Kirby-Bauer disk diffusion method and vancomycin MIC by agar dilution method and Etest (BioMerieux, France).
Results: Out of 98 strains of HA-MRSA, 94 (95.9%) were vancomycin susceptible (MIC ≤2 µg/ml and 4 (4.1%) were vancomycin intermediate (MIC
4 µg/ml) by agar dilution method. By Etest, 53 (54.1%) were vancomycin susceptible, 4 (4.1%) were vancomycin intermediate, and the remaining 41
isolates had vancomycin MIC between 2 µg/ml and 4 µg/ml.
Conclusion: Etest allows the detection of HA-MRSA strains with intermediate MIC values in addition to traditional dilutions. These properties will
help in detection of MIC creep and also decision-making in using vancomycin for the treatment of serious infections caused by HA-MRSA.
Keyword: Vancomycin, Minimum inhibitory concentration, Etest, Agar dilution.
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