Evaluation of Cefoxitin Disk Diffusion Test for Routine Detection of Methicillin-resistant Staphylococcus Aureus

Background and Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial and community acquired infections. Detection of MRSA in laboratories is veryimportant for treatment and appropriate infection control. The aim of this study was to evaluatecefoxitin disk diffusion method for detection of MRSA and comparison of this method with otherconventional methods. Methods: A total of 175 clinical isolates of S. aureus isolated from clinical specimens were studied. The isolates were identified by conventional laboratory methods. In this respect, E-testMIC, cefoxitin and oxacillin disk diffusion methods, and MAST ID Methicillin strips were used for detection of MRSA. All disk diffusion methods were performed as recommended by NCCL andmanufacturers’ guidelines. Results: Using E-test MIC, 53 out of 175 strains of S. aureus were resistant to methicillin.In addition, disk diffusion method using oxacillin disk showed that 52 strains are resistant to methicillin. In this respect, 8 strains had intermediate resistance to methicillin. For cefoxitin diskdiffusion method, 52 strains were resistant to methicillin. This method had a good correlation withE-test MIC method. Meanwhile, MAST ID methicillin strips detected 47 strains that were resistant to mehicillin. Sensitivity and specificity for both cefoxitin and oxacillin disk diffusion methods were 98%and 100% respectively. However cefoxitin was better than oxacillin for detecting intermediateresistant strains of S. aureus. Sensitivity and specificity for MAST ID methicillin strips were 91% and 100% respectively. Conclusion: This study revealed that cefoxitin disk diffusion method is a good alternative for oxacillin disk diffusion method for detection of MRSA. This method is more reliable for identification of intermediate resistant strains of S. aureus.

کلیدواژه ها:

Methicillin-resistant Staphylococcus aureus ، Cefoxitin