Methicillin-resistant Staphylococcus aureus: comparison of susceptibility test methods with mecA gene analysis for determining oxacillin (methicillin) resistance in our clinical isolates.

The aim of the study was to determine which of the following susceptibility test methods, using recommended or modified NCCLS, best detects oxacillin resistance: disk diffusion, agar screen, and broth dilution. PCR for mecA was used as "gold standard". We studied 120 Staphylococcus aureus isolates received from different patients hospitalized at the Clinical center in Skopje from May 2001 to November 2003. There were no two isolates from the same patient. Methicillin resistance in Staphylococcus aureus strains was performed according to the recommendations of the National Committee for Clinical Laboratory Standards (NCCLS). PCR appears to be promising. Since variations among the methods exist and no acceptable guidelines are formulated, a combination of conventional methods, including either 3 microg of oxacillin/ml. in Mueller Hinton broth or one of the screen agar plates (6 microg/ml), alone or with PCR should be the method of choice for the detection of MRSA. (Tab. 4, Ref. 12.)