Relationships in anesthesia work areas between contamination measured as colony-forming units, Staphylococcus aureus detection, and S. aureus transmission

Abstract Purpose Earlier, patients developed surgical site infection for 2.0% of cases without Staphylococcus aureus transmission through anesthesia work areas, 11% with S. aureus transmitted susceptible to prophylactic antibiotic, and 18% with transmission of antibiotic-resistant isolates. A randomized trial and an effectiveness study both found that anesthesiologists who used basic preventive measures (e.g., alcohol releasing intravenous caps) and received feedback on colony-forming units per surface area sampled (CFU) had reduced S. aureus transmission and postoperative healthcare-associated infections. We used prospectively collected data to evaluate whether CFU would be a reliable criterion for hospitals to assess anesthesiologists’ contributions to postoperative infections. Methods During the summer of 2025, reservoirs (e.g., anesthetist’s hands at case start/end) were sampled during 81 cesarean delivery cases performed in the same operating room. There were ≤ 15 reservoirs sampled per case. Results 52/1016 reservoir samples had S. aureus detected, more often with greater CFU ( P = 0.0063). The 159/1016 samples with < 100 CFU had no S. aureus . Total CFU of all reservoirs for each case to total S. aureus isolates was 2.50 × 10 9 per S. aureus (standard error 0.53 × 10 9 , N = 81 cases). CFU and S. aureus transmission were uncorrelated (all 15 reservoirs’ unadjusted P ≥ 0.12, Holm-Bonferroni P > 0.99). Conclusions With substantive contamination (≥ 100 CFU), so few isolates are S. aureus that surrogate measures of insufficient disinfection (e.g., ATP bioluminescence) are inaccurate markers both of S. aureus isolation and transmission. The lack of association between contamination and transmission shows that feedback on CFU provides information on the effectiveness of disinfection, not on S. aureus transmission.