Evaluation for the Novel mecC MethicillinResistance among Methicillin ResistantStaphylococcal Isolates in two EgyptianUniversity Hospitals

Abstract

Methicillin resistance adds to the threat of staphylococcal infections in humans. The gene for methicillin resistance in staphylococci is not only mecA gene as it was thought. The recently discovered mecC gene in animal and human isolates also encodes for methicillin resistance. The prevalence of the novel gene may be underestimated. It is discovered so far in Europe with low prevalence. This study evaluates the existence of mecC gene in two Egyptian university hospitals. A total of 600 methicillin resistant (520 MRSA and 80 MRCoNS) isolates from two university hospitals were screened for discrepancy in susceptibility between cefoxitin (30 μg) and oxacillin (1 μg) by disc diffusion as a method that could be used to predict the potential existence of mecC gene whose protein product has noticeably higher affinity for oxacillin. Discordant isolates included in selected 150 samples (110 MRSA and 40 MR-CoNS) were tested by PBP2a latex agglutination test, and or conventional PCR for mecA gene. Samples negative for mecA gene were tested for oxacillin and cefoxitin MIC by Vitec II and for mecC gene by PCR. All discrepant isolates were positive for PBP2a latex agglutination and mecA PCR, while the 6 isolates (5.5%) negative for mecA by PCR were resistant to both cefoxitin and oxacillin by disc diffusion and by Vitec II. In addition, those 6 isolates negative for mecA were also negative for mecC gene. Thus mecC gene for methicillin resistance couldn’t be detected in this study, though this may be baseline for further prevalence studies.