Weekly terminal cleaning is recommended to maintain low airborne bacterial counts in operating rooms.

OBJECTIVE: To identify the maximum recommended duration between terminal cleaning events in small animal veterinary operating rooms (ORs) and explore factors contributing to increased airborne microbial load. METHODS: An observational study using agar settle plates was completed to measure the Index of Microbial Air contamination (IMA) across ORs in a veterinary teaching hospital over a 2-year period. Plates were exposed for 60 minutes during surgeries and incubated for 48 hours to measure IMA. RESULTS: The median IMA for 192 collected cases was 4.3, below the published OR benchmark of 25 IMA, with a median terminal cleaning interval of 48 hours. Univariable linear regression implied that increasing time after terminal cleaning was associated (β = 0.002; 95% CI, 0.0002 to 0.003) with an increase in air contamination. For each 10-hour delay in cleaning, bacteria count increased by 1.04 IMA. Significant associations were also found between IMA and total number of personnel in the OR. In exploratory univariable analyses, significant relationships were not identified between IMA and procedure classification, number of scrubbed personnel, or postoperative surgical site infection. CONCLUSIONS: Settle plates offer a practical, cost-effective method for monitoring air hygiene and evaluating cleaning protocols. Our methodology confirms that terminal cleaning has a measurable effect in reducing OR air contamination and indicates weekly terminal cleaning events to maintain appropriate OR airborne microbial counts would be beneficial. CLINICAL RELEVANCE: Terminal cleaning should be completed at least every 10 days in veterinary ORs to keep microbial air contamination at levels below the working OR threshold of 25 IMA.