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.
Highlights
Methicillin resistant S. aureus (MRSA) was first described in 1961 collapsing the treatment options for staphylococcal infections as MRSA exhibits resistance to all B lactam antibiotics except 5th generation cephalosporins
It was thought that the only gene for methicillin resistance in staphylococci is mecA gene that encodes a transpeptidase PBP2a which has low affinity for ß lactams allowing cell wall synthesis to continue in the presence of the antibiotic
Isolates tested for mecA by conventional Polymerase chain reaction (PCR) included isolates tested by PBP2a latex agglutination and randomly selected isolates From Beni-Suef University Hospital which lies in a semirural area
Summary
Methicillin resistant S. aureus (MRSA) was first described in 1961 collapsing the treatment options for staphylococcal infections as MRSA exhibits resistance to all B lactam antibiotics except 5th generation cephalosporins. In this study we tried to evaluate the existence of mecC gene in methicillin resistant staphylococcal isolates obtained from two university hospitals in Egypt. A total of 600 sequential samples of methicillin resistant staphylococcal clinical isolates (520 MRSA and 80 MR-CoNS) were collected from clinical microbiology laboratories of two university hospitals in the duration from March 2014 to May 2016.
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