Evaluation of cefoxitin disc diffusion test as a rapid phenotypic method for detection of methicillin resistance

Abstract

: Accuracy and promptness in the detection of methicillin resistance are of key importance in ensuring correct antibiotic treatment in infected patients and control of MR staphylococci in the hospital environment. The aim of this study was to detect MRSA phenotypically by oxacillin screen agar and Oxacillin MIC method and to evaluate cefoxitin disc diffusion test as a screening tool for MRSA detection. In the present study, a total of 50 isolates of from various clinical samples collected were used for the detection of Methicillin resistant (MRSA). Methicillin resistance was determined by oxacillin disc diffusion, cefoxitin disc diffusion the oxacillin screen agar test and MIC. Out of 50 isolates 21 (42%) isolates were detected as MRSA based on MIC method, which is considered as gold standard method for the detection of MRSA. All the isolates of MRSA were 100% susceptible to vancomycin and linezolid. rnIn the present study, cefoxitin diffusion method has given 100% sensitivity and specificity in concordance with MIC method. However, the oxacillin screen agar method showed 95.24% sensitivity and 96.55% specificity. As per our study and previous reports elsewhere on phenotypic detection of MRSA, cefoxitin is more potent inducer of the regulatory system and an accurate surrogate marker for the detection of MRSA in the routine susceptibility testing.