The molecular evolution of methicillin-resistant Staphylococcus aureus

Abstract

Staphylococcus aureus is a potentially pathogenic bacterium that causes a broad spectrum of diseases. S. aureus can adapt rapidly to the selective pressure of antibiotics, and this has resulted in the emergence and spread of methicillin-resistant S. aureus (MRSA). Resistance to methicillin and other beta-lactam antibiotics is caused by the mecA gene, which is situated on a mobile genetic element, the Staphylococcal Cassette Chromosome 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 genes for resistance to beta-lactam antibiotics, as well as genes for the regulation of expression of mecA. Additionally, SCCmec types II and III carry non-beta-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 on at least 20 occasions 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 types 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.

Biofilm formation in invasive Staphylococcus aureus isolates is associated with the clonal lineage

“…Our study did not supplement glucose which may have affected the MRSA biofilm capabilities. Our selection criteria was based on the genotypic classification which is also a limiting factor as some clones may be associated with methicillin-resistance (Deurenberg et al, 2007).…”

“…Pulsed-field gel electrophoresis (PFGE) is considered the reference standard for S. aureus strain typing and is the most discriminatory typing method (Deurenberg et al, 2007;Oosthuysen et al, 2013). The method described by McDougal et al was followed (McDougal et al, 2003).…”

Characterisation of the Virulence Factors and Genetic Types of Methicillin Susceptible Staphylococcus aureus from Patients and Healthy Individuals

“…PCR-RFLP of coa gene is based on the restriction digest of the heterogeneity of the coagulase region that contains the 81 bp tandem repeats at 3 0 coding region [11] whereas PFGE is based on digestion of chromosomal DNA with the restriction enzyme followed by agarose gel electrophoresis [12]. On the other hand, spa typing is based on the sequence analysis of polymorphic region X of S. aureus protein A is reported to be a highly effective tool in subtyping S. aureus [12].…”

Offsetting virulence and antibiotic resistance costs by MRSA

“…Methicillin resistance is conferred by the acquisition of a piece of DNA referred to as the SCCmec element (Deurenberg et al, 2007). The size and content of this element vary and is currently classified into five major groups (SCCmec types I-V) based on their content (Deurenberg et al, 2007).…”

“…The size and content of this element vary and is currently classified into five major groups (SCCmec types I-V) based on their content (Deurenberg et al, 2007). There are two features common to all SCCmec elements: the mecA gene, which encodes the alternative penicillin-binding protein that confers methicillin resistance, and the ccr recombination sites and associated recombinases that cause this mobile piece of DNA to excise and transmit horizontally (Hiramatsu et al, 2001).…”