Accuracy of oxacillin susceptibility testing methods for Staphylococcus aureus

Since oxacillin is the first-choice drug in the treatment of methicillin-susceptible Staphylococcus aureus infections, correct assessment of oxacillin susceptibility is mandatory. METHODS: One hundred and fifty-six S.aureus strains have been used to evaluate the accuracy of disk diffusion method (1 μg oxacillin disk and 30 μg cefoxitin disk), detection of minimum inhibitory concentration of oxacillin (E-test), and a latex-agglutination test for detection of PBP2a compared with detection of mecA gene by a real-time PCR technique as gold standard. RESULTS: The mecA gene was detected in 68 strains. Sensitivities of the evaluated methods were 98.5%, 100%, and 100%, while specificities were 100% for all three of them. CONCLUSIONS: Accuracy of phenotypic methods for assessment of oxacillin resistance approaches that of detection of mecA for S.aureus isolates