Khawaja A, Arshad F, Asif M, Ahmad S, Yunus N, Hameed A.
Molecular Evaluation of Methicillin Resistant Staphylococcus Aureus Isolates at a Tertiary Care Hospital in Lahore.
Biomedica Jan ;35(1):24-7.

Background and Objectives: The versatility of Staphylococcus aureus has been transformed as "Methicillin resistant Staphylococcus aureus". Among phenotypic methods for detection of MRSA, feasible technique, i.e., cefoxitin disc diffusion test and/or oxacillin disc diffusion test can significantly contribute towards reliable detection. To determine methicillin resistance in Staphylococcus aureus by disc diffusion methods; and to evaluate their accuracy with mecA gene PCR for MRSA detection. Methodology: A total of 750 staphylococcus aureus isolates were screened with oxacillin disk (1 ?g) and cefoxitin disk (30 ?g) by Kirby-Bauer method using CLSI guideline (2016); to get 105 continuous, nonrepetitive clinical isolates of MRSA. All the methicillin resistant staphylococcus aureus isolates were further amplified by polymerase chain reaction for mecA gene detection. Results: All the 105 MRSA isolates were resistant by both oxacillin and cefoxitin disk diffusion tests. On PCR amplification, out of 105 MRSA (oxacillin resistant) isolates, 83 (79.04%) isolates were positive for mecA gene. Among 105 MRSA (cefoxitin resistant) isolates, 89 (84.76%) were mecA gene positive, by PCR amplification. The sensitivity (96.73%) and diagnostic accuracy (94.28%) of cefoxitin disc diffusion method was higher than oxacillin disc diffusion technique, with reference to PCR as a gold standard. Conclusion: Cefoxitin disc diffusion method can be employed reliably for detection of mecA gene in MRSA isolates in settings with limited resources, where molecular methods are not available. This can efficiently reduce the misdiagnosis and dissemination of resistant strains.

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