[Comparison of different detection methods for methicillin resistance in Staphylococcus aureus]

The investigation of methicillin resistance in Staphylococcus aureus (MRSA) is a serious problem for the physician and microbiologist. Accurate and rapid detection is essential for the use of appropriate antimicrobial therapy and for the control of nosocomial spread of the resistant strain. The performance characteristics of the MicroScan Overnight Conventional Pos Combo 12 panels (MOCP), BBL Crystal MRSA ID (CR), E-test and agar screen plate (Muller Hinton agar with oxacillin 6 micrograms/ml and 4% NaCl) (AS) were evaluated for the detection of oxacillin resistance. Thirty S. aureus clinically significant strains with different PFGE (Pulse Field Gel Electrophoresis) banding pattern were tested, and 22 of them were mecA positive by PCR. These strains were also analyzed by mecA and Tn554 polymorphism. All mecA positive strains were classified as methicillin resistant by MOCP and E-test. CR and AS failed to detect oxacillin resistance in 2 strains. One false positive was only detected by E-test. Accurate testing for the presence of MRSA may reduce the need for empiric therapy with vancomycin for patients with staphylococcal infections. According to our results the best performance was obtained with MOCP. However, as a rapid method, CR gave acceptable sensitivity for clinical purposes.