Version 2: Staphylococcus aureus  associated with post-operative wound infections in Western Kenya reveals genomic hotspots for pathogen evolution

Objectives.  Staphylococcus aureus is one of the most common pathogens attributed to hospital infections. Although S. aureus infections have been well studied in developed countries, far less is known about the biology of the pathogen in sub-Saharan Africa.

Methods. Here, we report on the isolation, antibiotic resistance profiling, whole genome sequencing, and genome comparison of six multi-drug resistant isolates of S. aureus obtained from a referral hospital in Kakamega, Western Kenya.

Results. Five of the six isolates contained a 20.7-kb circular plasmid carrying blaZ (associated with resistance to b-lactam antibiotics). These five strains all belonged to the same sequence type, ST152. Despite the similarity of the plasmid these isolates, whole genome sequencing revealed that the strains differed, depending on whether they were associated with hospital-acquired or community-acquired infections.

Conclusion. The intriguing finding is that the hospital acquired and the community acquired isolates of S. aureus belonging to the same genotype ST152 formed two separate sub-clusters in the phylogenetic tree and differed by the repertoire of accessory virulence genes suggesting an ongoing adaptive evolution and significant genomic plasticity.