Evaluation of a cefoxitin disk diffusion test for the routine detection of methicillin-resistant Staphylococcus aureus.

Two oxacillin disk methods were compared with a cefoxitin disk diffusion test for detection of methicillin-resistant Staphylococcus aureus (MRSA), with PCR for mecA as the reference method. When tested with 115 MRSA and 350 methicillin-susceptible S. aureus isolates, the cefoxitin disk test (specificity 100%, sensitivity 96.5%) was superior to the oxacillin disk methods (specificity 99.1%, sensitivity 90.4%). Testing with both oxacillin and cefoxitin disks would give better sensitivity (100%) than the cefoxitin test alone, but at the expense of specificity (99.1%). The cefoxitin disk test required no special test conditions and would improve the reliability of routine tests for detection of MRSA.