Searching for links between environmental and clinical mecA⁺Staphylococcus aureus: A comparative genomics study

Area of Science:

• Microbiology
• Genomics
• Evolutionary Biology

Background:

• Staphylococcus aureus, particularly methicillin-resistant strains (MRSA) due to the mecA gene, are significant public health threats.
• The ubiquity of S. aureus necessitates understanding its ecological dynamics and potential for adaptation.

Purpose of the Study:

• To investigate the genomic relatedness and adaptive potential of environmental mecA+ S. aureus compared to clinical isolates.
• To determine if environmental MRSA strains can thrive as clinical isolates and identify associated accessory genome features.

Main Methods:

• Comparative genomic analysis of 111 environmental and 103 clinical mecA+ S. aureus isolates.
• Phylogenetic analysis, core-genome analysis, and accessory genome profiling.
• Identification of clinically relevant genes, including those for antibiotic resistance and virulence.

Main Results:

• Environmental and clinical mecA+ S. aureus isolates share common phylogenetic backgrounds (MLSTs).
• Environmental isolates showed significantly higher frequencies of genes conferring resistance to beta-lactams, aminoglycosides, and macrolides, alongside enterotoxin and serine protease genes.
• Clinical isolates were enriched for genes related to macrolide/phenicol resistance, fosfomycin resistance, leucocidin, and serine protease functions.

Conclusions:

• mecA+ S. aureus demonstrates exchangeability between clinical and environmental niches.
• Accessory genome variations, including antibiotic resistance and virulence factors, are likely associated with specific habitats, indicating bacterial adaptation.
• The interplay between phylogeny and accessory genome aids in understanding MRSA ecology and evolution.