Evolution of community- and healthcare-associated methicillin-resistant Staphylococcus aureus

Abstract

Staphylococcus aureus is a prominent cause of human infections globally. The high prevalence of infections is compounded by antibiotic resistance--a significant problem for treatment. Methicillin-resistant S. aureus (MRSA) is endemic in hospitals and healthcare facilities worldwide, and is an increasingly common cause of community-associated bacterial infections in industrialized countries. Although much focus is placed on the role of S. aureus as a human pathogen, it is in fact a human commensal organism that has had a relatively long coexistence with the human host. Many S. aureus infections can be explained by host susceptibility or other predisposing risk factors. On the other hand, the emergence/re-emergence of successful S. aureus clones (referred to as epidemic waves) suggests a rapid bacterial adaption and evolution, which includes the emergence of antibiotic resistance and increased virulence and/or transmissibility. It is within this context that we review our understanding of selected S. aureus epidemic waves, and highlight the use of genome sequencing as a means to better understand the evolution of each lineage.

Keywords: Antimicrobial resistance; Epidemic; Genome sequencing; MRSA; Staphylococcus aureus.

Fig. 1

Phylogenetic analyses of selected CC30 strains/isolates. Left panel is a phylogenetic analysis of CC30 strains (indicated by dots or labeled as EMRSA-16) based upon analysis of a contiguous 1.4 Mb region of the genome. Right panel is a phylogenetic analysis of CC30 strains based upon concatenated SNPs in the core genome. SWP, Southwest Pacific clone; 80/81, phage type 80/81 S. aureus; Contemporary HA, contemporary hospital CC30 isolates. Adapted from DeLeo et al. (2011).