Comparison of mecA polymerase chain reaction with phenotypic methods for the detection of methicillin-resistant Staphylococcus aureus.

In the present study, several conventional methods to detect methicillin-resistant Staphylococcus aureus (MRSA) were compared with polymerase chain reaction (PCR) detection of mecA gene-positive isolates. Cefoxitin E-test was also evaluated as a possible phenotypic method of MRSA detection. Oxacillin agar screen and PBP2' latex agglutination methods were found to be more sensitive than oxacillin and cefoxitin disk-diffusion methods. Cefoxitin disk diffusion was found to be the most specific. A combination of oxacillin agar screening with cefoxitin disk diffusion, or oxacillin disk diffusion with PBP2', improved sensitivity and specificity. Cefoxitin E-test with the current break points had low sensitivity and specificity (33.3% and 75%, respectively) for the detection of MRSA. However, changing the break points to or= 6 microg/ml for sensitive and resistant, respectively, greatly improved both. Changing the 30-microg cefoxitin disk-diffusion break points to