Diagnostic Test Validity of Oxacillin Screen Agar for the Detection of Methicillin Resistant <i>Staphylococcus aureus</i>

Abstract

Background: Detection of Methicillin Resistant Staphylococcus aureus may vary in phenotypic and genotypic methods. Objective: The aim of this present study was to validate the oxacillin screen agar test for the detection of methicillin-resistant Staphylococcus aureus isolated from clinical specimens. Methodology: This cross-sectional study was planned to carry out in the Department of Microbiology and Immunology at Bangabandhu Sheikh Mujib Medical University, Dhaka from January, 2010 to December, 2010 for a period of one (01) year. Different clinical specimens were collected from the patients presented with infections at anybody sites. Isolation and identification of Staphylococcus aureus (S. aureus) were performed by staining, culture and biochemical tests. Oxacillin screen agar test was performed to detect the methicillin-resistant Staphylococcus aureus. PCR was performed for detection of the mecA gene for MRSA. Result: Out of the 22 suspected MRSA isolates 19 were mecA positive by PCR. The sensitivity and specificity of oxacillin screen agar were 100.0% (95% CI 82.3 to 100.0%) and 33.3% (95% CI 24.0 to 90.6%) respectively. The positive predictive value and negative predictive value of oxacillin screen agar test were 90.5% (95% CI 81.0 to 95.5%) and 100.0% (95% CI 20.6 to 100.0%) respectively. The accuracy of the oxacillin screen agar test was 90.9% (95% CI 71.7 to 96.3%). Conclusion: In conclusion oxacillin screen agar test has high sensitivity with low specificity for the detection of MRSA.