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Published on: March 17, 2023
Relationships in anesthesia work areas between contamination measured as colony-forming units, Staphylococcus aureus
Arnav Bhushan1, Franklin Dexter1, Carmen Brindeiro2
1Department of Anesthesia, University of Iowa, 200 Hawkins Dr, Iowa City, IA 52242 USA.
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 × 109 per S. aureus (standard error 0.53 × 109, 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.
Supplementary Information:
The online version contains supplementary material available at 10.1007/s44254-026-00169-y.
Insights
Colony-forming units (CFU) do not reliably indicate Staphylococcus aureus transmission in operating rooms. Feedback on CFU measures disinfection effectiveness, not bacterial spread, impacting infection control strategies.
Area of Science:
- Healthcare epidemiology
- Infection prevention and control
- Microbiology
Background:
- Surgical site infections (SSIs) are a significant concern, with Staphylococcus aureus transmission contributing to increased patient risk.
- Previous studies indicated that basic preventive measures and feedback on colony-forming units (CFU) per surface area could reduce S. aureus transmission and SSIs.
- Hospitals seek reliable methods to assess anesthesiologists' impact on postoperative infection rates.
Purpose of the Study:
- To evaluate if colony-forming units (CFU) serve as a dependable criterion for hospitals to assess anesthesiologists' contributions to postoperative infections.
- To determine the correlation between CFU counts on reservoirs and S. aureus transmission during surgical procedures.
Main Methods:
- Prospective data collection during 81 cesarean delivery cases in a single operating room.
- Sampling of up to 15 reservoirs (e.g., anesthetist's hands) per case during the summer of 2025.
- Quantification of S. aureus and total CFU on sampled reservoirs.
Main Results:
- 52 out of 1016 reservoir samples (5.1%) detected S. aureus, with higher CFU counts correlating with increased detection (P=0.0063).
- Samples with <100 CFU/reservoir showed no S. aureus.
- CFU counts were uncorrelated with S. aureus transmission (P > 0.99 after adjustment).
Conclusions:
- Colony-forming units (CFU) are not a reliable indicator of Staphylococcus aureus transmission in the operating room.
- Feedback on CFU primarily reflects disinfection effectiveness, not the actual spread of S. aureus.
- Surrogate measures of disinfection may be inaccurate for assessing S. aureus isolation and transmission, especially with high contamination levels.
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