Comparison of different methods for the detection of methicillin resistant Staphylococcus aureus

Methicillin-resistant (MRSA) is responsible for an increasing number of serious nosocomial and community-acquired infections. Phenotypic heterogeneous drug resistance to antistaphylococcal beta-lactams affects the results of susceptibility testing.The aim of this study was to compare the specificity and sensitivity of the oxacillin and cefoxitin disk diffusion, E-test, MRSA latex agglutination and the oxacillin agar screen tests, with PCR for the mecA gene (Genotype MRSA) used as the ?gold standard? assay.Of the 100 clinical isolates of S. aureus tested with Genotype MRSA 90 were determined as mecA positive. While the specificities of all methods were found as 100 %, the cefoxitin and oxacillin disk diffusion, E-test and the oxacillin agar screen test showed sensitivities of 86.6, 91.0, 88.8, and 95.6%, respectively. MRSA latex aglutination test for detection of PBP2a corresponded 100% with the results of Genotype MRSA.Our results indicated that, the oxacillin disk diffusion method was the best perfoming test for routine detection of MRSA in our laboratory. MRSA latex agglutination test is more accurate than any susceptibility testing method and can be use as confirmatory test when necessary.Key words: Staphylococcus aureus, methicillin resistance, mecA