Antimicrobial resistance profiling and molecular typing of methicillin-resistant Staphylococcus aureus isolated from a Malaysian teaching hospital

The annual prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in Malaysia has been estimated to be 30 % to 40 % of all S. aureus infections. Nevertheless, data on the antimicrobial resistance and genetic diversity of Malaysian MRSAs remain few. In 2009, we collected 318 MRSA strains from various wards of our teaching hospital located in Kuala Lumpur, the capital city of Malaysia, and performed antimicrobial susceptibility testing on these strains. The strains were then molecularly characterized via staphylococcal cassette chromosome (SCC) mec and virulence gene (cna, sea, seb, sec, sed, see, seg, seh, sei, eta, etb, Panton-Valentine leukocidin and toxic shock syndrome toxin-1) typing; a subset of 49 strains isolated from the intensive care unit was also typed using PFGE. Most strains were found to be resistant to ciprofloxacin (92.5 %), erythromycin (93.4 %) and gentamicin (86.8 %). The majority (72.0 %) of strains were found to harbour SCCmec type III-SCCmercury with the presence of ccrC, and carried the sea+cna gene combination (49.3 %), with cna as the most prevalent virulence gene (94.0 %) detected. We identified four PFGE clusters, with pulsotype C (n=19) as the dominant example in the intensive care unit, where this pulsotype was found to be associated with carriage of SCCmec type III and the sea gene (P=0.05 and P=0.02, respectively). In summary, the dominant MRSA circulating in our hospital in 2009 was a clone that was ciprofloxacin, erythromycin and gentamicin resistant, carried SCCmec type III-SCCmercury with ccrC and also harboured the sea+cna virulence genes. This clone also appears to be the dominant MRSA circulating in major hospitals in Kuala Lumpur.