Characterizing the Molecular Epidemiology of Anaesthesia Work Area Transmission of Staphylococcus aureus ST5.

BACKGROUND: Staphylococcus aureus sequence type 5 (ST5) is an emerging global threat. Our primary goal was to characterize the epidemiology of ST5 transmission in the anaesthesia work area.

METHODS: The retrospective cohort study analysed transmitted, prophylactic antibiotic resistant Staphylococcus aureus isolates involving anaesthesia work area reservoirs. Using whole genome analysis, the epidemiology of ST5 transmission was characterized by reservoir(s) of origin, transmission location(s), portal of entry, and mode(s) of transmission. All patients were followed for at least 30 days for surgical site infection development.

RESULTS: Forty-one percent (18/44, 95% CI 28-56%) of isolates were ST5. Provider hands were the reservoir of origin for 28% (5/18) of transmitted ST5 vs. 4% (1/26) for other ST. Provider hands were the transmission location for 28% (5/18) of ST5 vs. 7% (2/26) of other ST. Stopcock contamination occurred for 8% (1/13) of ST5 isolates versus 12% (3/25) of other ST. Sixty-three percent of transmission events occurring between cases on separate operative dates involved ST5. ST5 was more likely to harbour resistance traits (ST5 median [interquartile range] 3 [2-3] vs. other ST 2 [1-2], P < 0.001) and had greater resistance to cefazolin, piperacillin-tazobactam, and/or ciprofloxacin (ST5 3 [2-3] vs. 2 [1-3] other ST, P=0.02). ST5 was associated with three of six SSIs.

CONCLUSIONS: ST5 is prevalent among transmitted, prophylactic antibiotic resistant isolates in the anaesthesia work area. Transmission involves provider hands and one patient to another on future date(s). ST5 is associated with a greater number of resistance traits and reduced in vitro susceptibility vs. other intraoperative MRSA.