High-level disinfection of gastrointestinal endoscopes: Are current guidelines adequate?

OBJECTIVE: For a germicide to obtain a high level disinfection (HLD) claim, EDA requires demonstration of a 6-log reduction of mycobacterial inoculum under worst case conditions. The purpose of this study was to assess the ad equacy of current guidelines for high level disinfection of GI endoscopes u sing alkaline glutaraldehyde in simulated-use testing. METHODS: Various gastrointestinal endoscopes were contaminated with Mycobac terium chelonae in 46 experiments. Quantitative cultures were obtained from each endoscope channel separately after each step: inoculation, standardiz ed manual cleaning, immersion in 2% glutaraldehyde (Cidex) for 10, 20, or 4 5 min at room temperature, 70% isopropanol rinse, and drying. RESULTS: Manual cleaning alone achieved a 4-log reduction. After 10 min of glutaraldehyde exposure, but before alcohol rinse, two of 10 experiments fa iled to achieve a 6-log reduction. However, after alcohol rinse, all 10 exp eriments achieved HLD. After 20 min of glutaraldehyde exposure, but before alcohol rinse, one of 18 experiments failed to achieve a 6-log reduction. A fter alcohol rinse, all 18 experiments achieved HLD. After 45 min of glutar aldehyde exposure, but before alcohol rinse, one of 18 experiments failed t o achieve a 6-log reduction. After alcohol rinse, all 18 experiments achiev ed HLD. Thus, if the entire reprocessing protocol including manual cleaning , glutaraldehyde exposure, alcohol rinse, and drying was taken into account , the required 6-log reduction of mycobacteria was achieved with a minimum of 10 min of glutaraldehyde exposure at room temperature. CONCLUSIONS: Current guidelines for high level disinfection using glutarald ehyde are appropriate. Alcohol rinse is a valuable adjunctive step for dryi ng and for its bactericidal effects. (Am J Gastroenterol 1999;94:1546-1550. (C) 1999 by Am. Coll. of Gastroenterology).