Characterization of nasal methicillin-resistant Staphylococcus aureus isolated from international human and veterinary surgeons

Purpose. Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is poorly described for surgeons, despite the increased exposure to nosocomial pathogens and at-risk patients. This study investigated the molecular epidemiology and antimicrobial resistance of 26 MRSA isolates cultured from the nares of an international cross-sectional study of 1166 human and 60 veterinary surgeons. Methodology. All isolates were subjected to agr, spa and multilocus sequence typing, and the presence of 22 virulence factors was screened for by PCR. Additionally, biofilm-forming ability, haemolytic activity, staphyloxanthin production and antibiotic resistance were determined. The genome of a rifampicin-resistant MRSA was sequenced. Results. Approximately half of the isolates belonged to well-described clonal lineages, ST1, ST5, ST8, ST45 and ST59, that have previously been associated with severe infections and increased patient mortality. Two of the three veterinarian MRSA belonged to epidemic livestock-associated MRSA clonal lineages (ST398 and ST8) previously associated with high transmission potential between animals and humans. The isolates did not display any consistent virulence gene pattern, and 35% of the isolates carried at least one of the Panton-Valentine leukocidin (lukFS-PV), exfoliative toxin (eta) or toxic shock syndrome (tst) genes. Resistance to rifampicin was detected in one veterinarian isolate and was found to be due to three mutations in the rpoB gene. Conclusion. Surgeons occupy a critical position in the healthcare profession due to their close contact with patients. In this study, surgeons were found to be colonized with MRSA at low rates, similar to those of the general population, and the colonizing strains were often common clonal lineages.