Dania Aijaz Shah, Shehnaz Wasim, Farhan Essa Abdullah.
Comparison of Oxacillin and Cefoxitin for the Detection of mecA Gene to Determine Methicillin Resistance in Coagulase Negative Staphylococci (CoNs).
J Coll Physicians Surg Pak Jan ;27(8):520-2.

The aim of the study was to compare the effectiveness of Cefoxitin with that of Methicillin/Oxacillin in the determination of mecA gene in Methicillin resistant Coagulase-negative staphylococci (CoNS). We assessed 57 CoNS isolates for mecA gene via PCR, which were subsequently subjected to Methicillin/Oxacillin and Cefoxitin disc diffusion test. These methods are simple, inexpensive and easily available compared to PCR despite less specificity. Out of 41 mecA positive species, 33 (80.5%) were resistant to Methicillin/Oxacillin. Cefoxitin-resistance was seen in all 41 (100%) mecA positive samples. Two (12.5%) mecA negative isolates of S.saprophyticus were Methicillin/Oxacillin resistant, but were Cefoxitin sensitive. Four (9.7%) isolates of S.saprophyticus, three (7.3%) of S.epidermidis species, and one (2.4%) S.haemolyticus that were mecA positive were sensitive to Methicillin/Oxacillin but resistant to Cefoxitin. Cefoxitin resistance provides a more accurate picture of mecA gene positivity as compared to Methicillin and Oxacillin.

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