An 18-month pilot microbiological evaluation of sterilized operating room supplies stored under routine clinical conditions at a single hospital in Japan

Time-related sterility maintenance (TRSM) remains common in Japanese operating rooms (ORs), requiring routine re-sterilization of unopened supplies. Event-related sterility maintenance (ERSM), which defines loss of sterility based on contamination events rather than elapsed time, may reduce unnecessary reprocessing and associated burden. This study reports a pre-specified 18-month pilot interim analysis of a prospective observational evaluation of ERSM. This single-center prospective observational study was conducted in a tertiary-care OR. Representative materials (titanium instruments, cotton, and latex) were sterilized using steam, ethylene oxide, or vaporized hydrogen peroxide, double-bagged and heat-sealed in ISO 11607-1–compliant sterile barrier systems, and stored in closed cabinets at three OR locations under routine clinical handling. Sterility testing followed the Japanese Pharmacopoeia (18th edition) sterility test (4.06), harmonized with USP and Ph. Eur. 2.6.1. At 18 months, all 18 cultured items showed no microbial growth (0/18) across all sterilization modalities and storage locations. These interim findings are descriptive and suggest feasibility only; the ongoing protocol will continue to the planned 60-month evaluation.