V. POST¹, L.G. HARRIS², M. MORGENSTERN³, R.G. RICHARDS¹, T.F. MORIARTY<sup>1

1</sup>AO Research Institute, AO Foundation, Davos Switzerland, ²University of Swansea, Swansea, United Kingdom, ³BGU Murnau, Murnau Germany

Staphylococci are common opportunistic pathogens colonizing the human population. The data available to date on nasal colonization in surgeons has been limited. A prospective study was undertaken in late 2013. The aim was to identify the prevalence of staphylococci (S. aureus/methicillin-resistant S. aureus (MRSA) and coagulase-negative staphylococci (CoNS/MRCoNS)) in an international cohort of surgeons. Nasal swabs and basic demographic data were collected from participants at an international educational event, on an anonymous and voluntary basis. MRSA isolates were subjected to agr-, spa- and MLST 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 for these MRSA isolates. The genome of a rifampicin resistant MRSA was sequenced, due to the importance of this antibiotic in patients served by orthopedic surgeons. Amongst the 1,166 human surgeons, the average overall S. aureus nasal colonization rate was 28% and MRSA rate 2% while the MRSA rate for veterinary surgeons was 5%. MRCoNS nasal carriage rate was 21%. The 26 MRSA displayed no remarkable virulence gene pattern and 35% of the isolates carried at least one of the Panton-Valentine leukocidin lukFS-PV, the exfoliative toxin eta or the toxic shock syndrome tst genes. All isolates were resistant to multiple antibiotics. Resistance to rifampicin was due to 3 mutations in the rpoB gene. Half of the isolates belonged to well-described clonal lineages, ST1, ST5, ST8, ST45 and ST59 that are associated with severe infections and increased patient mortality. Two of the 3 veterinarian MRSA belonged to epidemic livestock-associated MRSA clonal lineages ST398 and ST8 associated with high transmission potential between animals and humans. In conclusions, surgeons are colonized by S. aureus and MRSA at broadly equivalent rates to the general population. Twenty-six surgeons were colonized with multiply antibiotic resistant MRSA and belonged to clonal lineages with high transmission potential and causing increased infection severity.