Phenotypic and Genotypic Characterization of Methicillin Resistance in Staphylococci Isolated from an Egyptian University Hospital

Abstract

Methicillin-resistant in <i>Staphylococci</i> is a serious public health issue. It is mostly encoded by the <i>mecA</i> gene. The <i>mecC</i> gene is a new <i>mecA</i> analog responsible for resistance to methicillin in some <i>Staphylococcal</i> clinical isolates. This <i>mecC</i> gene is still underestimated in Egypt. The aim of the current study was to detect <i>mecA and mecC</i> genes in clinical <i>Staphylococci</i> isolates from a tertiary care university hospital in Egypt compared to the different phenotypic methods. A total of 118 <i>Staphylococcus aureus</i> (<i>S. aureus</i>) and 43 coagulase-negative <i>Staphylococci</i> (CoNS) were identified from various hospital-acquired infections. Methicillin resistance was identified genotypically using the PCR technique and phenotypically using the cefoxitin disc diffusion test, oxacillin broth microdilution and the VITEK2 system in all <i>Staphylococcal</i> isolates. The <i>mecA</i> gene was detected in 82.2% of <i>S. aureus</i> and 95.3% of CoNS isolates, while all of the isolates tested negative for the <i>mecC</i> gene. Interestingly, 30.2% of CoNS isolates showed the unique character of inducible oxacillin resistance, being <i>mecA</i>-positive but oxacillin-susceptible (OS-CoNS). The dual use of genotypic and phenotypic methods is highly recommended to avoid missing any genetically divergent strains.