engleski

The molecular evolution of methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is a potential pathogenic bacterium that causes a broad spectrum of diseases. S. aureus can adapt rapidly to antibiotics, and this has resulted in the emergence of methicillin-resistant S. aureus (MRSA). Resistance to methicillin and other ß-lactam antibiotics is caused by the mecA gene, which is situated on a mobile genetic element, the Staphylococcal Chromosomal Cassette mec (SCCmec). To date, five SCCmec types (I-V) have been distinguished and several variants of these SCCmec types have been described. All SCCmec elements carry resistance genes to β -lactam antibiotics as well as genes for the regulation of expression of mecA. Additionally, SCCmec types II and III carry non-β -lactam antibiotic resistance genes on integrated plasmids and a transposon. The epidemiology of MRSA has been investigated by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), spa typing and SCCmec typing. Numerous MRSA clones have emerged and disseminated worldwide. SCCmec has been acquired at least twenty times by different lineages of methicillin-sensitive S. aureus. Although most MRSA strains are hospital-acquired (HA-MRSA), community-acquired MRSA (CA-MRSA) strains have now been recognised. CA-MRSA is both phenotypically and genotypically different from HA-MRSA. CA-MRSA harbours SCCmec type IV or V, and is associated with the genes encoding Panton-Valentine leukocidin. The prevalence of MRSA ranges from 0.6% in The Netherlands to 66.8% in Japan. This review describes the latest developments in knowledge concerning the structure of SCCmec, the molecular evolution of MRSA, the methods used to investigate the epidemiology of MRSA, and the risk-factors associated with CA-MRSA and HA-MRSA.

CA-MRSA; evolution; HA-MRSA; methicillin-resistant Staphylococcus aureus; review; Staphylococcus aureus

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