Evaluation of Oxacillin Disk Diffusion Test for the Phenotypic Detection of Methicillin Resistant Staphylococcus aureus

ABSTRACT

Background: Different phenotypic detection method for theMethicillin Resistant Staphylococcus aureus is available.Objective: The aim of this present study was to evaluate theoxacillin disk diffusion test for the detection of methicillinresistant Staphylococcus aureus isolated from clinicalspecimens.Methodology: This cross-sectional study was planned to carryout in the Department of Microbiology and Immunology atBangabandhu Sheikh Mujib Medical University, Dhaka fromJanuary, 2010 to December, 2010 for a period of one (01)year. Different clinical specimens were collected from thepatients presented with infections at anybody sites. Isolationand identification of Staphylococcus aureus (S. aureus) wasperformed by staining, culture and biochemical tests. Oxacillindisk diffusion test was performed to detect the methicillinresistant Staphylococcus aureus. PCR was performed fordetection of the mecA gene for MRSA.Results: Out of the 22 suspected MRSA isolates 19 weremecA positive by PCR. The sensitivity and specificity ofoxacillin disc diffusion method for the detection of MRSA was84.2% (95 CI 60.4 to 96.6%) and 66.2% (95% CI 9.4 to99.2%) respectively. The positive predictive value and negativepredictive value of oxacillin disc diffusion method were 94.1%(95% CI 76.1 to 98.8%) and 40.0% (95% CI 15.2 to 71.2%)respectively. The accuracy was 81.8% (95% CI 66.7 to 95.3%).Conclusion: Oxacillin disk diffusion test shows high sensitivitywith moderate specificity for the detection of MRSA fromclinical specimens.