Variations of agar screen tests for detection of methicillin resistance in staphylococci: focus on cefoxitin

Members of the genus Staphylococcus are among the most important human pathogens, and strains demonstrating resistance to methicillin are an increasing problem worldwide, both within and outside of hospital environments. The objective of this study was to evaluate the use of variations of agar screening tests with cefoxitin and oxacillin to detect methicillin resistance in staphylococcal isolates. The agar screening test with cefoxitin (4 μg/ml) showed 99.4% accuracy for detecting both S. aureus and coagulase-negative staphylococci. The performance of the agar screening test with cefoxitin (4 μg/ml) either equaled or was superior to the other agar screening test variations evaluated and can be used to characterize the presence of the mecA gene among staphylococcal species.