Airborne Bacterial Deposition Onto Surgical Sites Under Operating Room Versus Field Sterility: A Passive Air Sampling Study Across 3 Surgical Environments.

BACKGROUND: Airborne microbial contamination contributes to surgical site infections. While operating rooms (ORs) use specialized ventilation, many minor procedures are now performed outside the main suite using field sterility. This study compared airborne bacterial deposition across 3 clinical settings with differing sterility protocols.

METHODS: An observational environmental sampling study was conducted in a minor procedures room, a day surgery suite, and a main OR. Minor procedures and day surgery used identical field-sterility draping; the OR used full sterile draping. On each sampling day, 15 blood agar settle plates were exposed in 3 sequential 1-hour intervals (5 plates/hour) on a tray 1 m above the floor and 1 m from the operative field, following index of microbial air contamination principles. After 24-hour incubation at 37 °C, colony-forming units (CFUs) were counted (n = 180 total; 60 per environment). Mean CFU counts were compared using 1-way analysis of variance (ANOVA) with Tukey post hoc testing.

RESULTS: Overall differences in mean CFU counts across the 3 environments were statistically significant (1-way ANOVA, F = 23.10, P < .001). The minor procedures room had the highest mean CFU/plate at 3.48 (SD = 2.53), followed by the day surgery suite at 2.23 (SD = 1.47), and the OR at 1.17 (SD = 1.38). Tukey post hoc testing showed significantly higher counts in the minor procedures room compared with the OR (mean difference [MD] = 2.32, P < .0001) and day surgery suite (MD = 1.25, P = .0013). Day surgery counts were also significantly higher than the OR (MD = 1.07, P = .0058).

CONCLUSIONS: Airborne microbial deposition differed significantly across environments, lowest in the OR and highest in the minor procedures room. Despite identical field-sterility draping in minor procedures and day surgery, contamination levels varied, suggesting environmental factors beyond draping influence microbial burden and should be considered when evaluating procedural environments.