Susceptibility testing of methicillin-resistant Staphylococcus aureus with three commercial microdilution systems.
The antimicrobial susceptibilities of 100 methicillin-resistant Staphylococcus aureus isolates were determined concurrently by API Uniscept KB, Micro-Media, MicroScan, standardized disk diffusion, and reference broth microdilution to evaluate whether these commercial microdilution systems would reliably defect methicillin-resistant S. aureus. The methicillin minimal inhibitory concentration for all isolates was greater than or equal to 16 micrograms/ml as determined by the reference minimal inhibitory concentration panels containing 2% NaCl supplemented Mueller-Hinton broth. Using the breakpoints established by the National Committee for Clinical Laboratory Standards for reporting susceptible and resistant methicillin results, there was 100% agreement between the reference methods and API Uniscept KB at 24 hr. The Micro-Media and MicroScan systems had 47% and 8% very major discrepancies at 24 hr, respectively. At 48 hr, these two systems exhibited 15% and 0% very major discrepancies. Micro-Media and MicroScan were in agreement with the reference microdilution method (+/- 1 log2 dilution) for 62% and 68% of the strains at 24 hr, respectively and 88% and 85% of the isolates at 48 hr, respectively. The results of this study indicate that API Uniscept KB would provide a practical and reliable method for the detection of methicillin-resistant S. aureus.
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D006801:Humans; D008712:Methicillin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D013211:Staphylococcus aureus / Q000187:drug effects*
D000900:Anti-Bacterial Agents; D008712:Methicillin