Discrepancies in the identification of methicillin-resistant Staphylococcus aureus and the absence of mecC in surveillance isolates in South Africa

Abstract

We investigated instances of phenotypic and genotypic discrepancies in the identification of methicillin-resistant Staphylococcus aureus in a reference laboratory in South Africa. Organism identification and antimicrobial susceptibility testing were performed using automated systems; and, the detection of mecA, mecC and nuc was performed using real-time and conventional PCR methods. Staphylococcal cassette chromosome mec (SCCmec) typing was done using conventional typing methods. Ninety-nine percent of phenotypic and genotypic results correlated; however, there were some discrepancies. The mecC gene was not detected in any of isolates tested. Although modest in number, the awareness of potential discrepancies is important and should be noted. However, our findings suggest that such discrepancies are rare and that phenotypic identification methods are acceptable.