Shionogi Pharmacolog. Inc.; Fig. 1) and also from ESW-45 (Olympus Optical Comp.; Fig. 2). These machines continuously produce 750-1000 mL/min of SAEW from tap water and salt.We introduced SAEW as an endoscope disinfectant in 1994 and proved its efficacy and safety. 9 In this paper, we discuss the effect of SAEW compared with the use of GA by using experimentally contaminated endoscopes. were used in this experiment: half were upper GI endoscopes (Olympus video endoscope XQ200, XQ230) and the other half were colonoscopes (Olympus video endoscope CF200, CF230). Before the experiment, each endoscope was cleaned using an automatic reprocessor (Olympus OW30) with a 30-min soak in GA and alcoholic flush. Pseudomonas aeruginosa (ATCC 27853), Mycobacterium avium (ATCC 25291) and hepatitis B surface antigen (HbsAg) positive, e antigen positive blood were used as markers of contamination. Each bacterial suspension was prepared from precultures in sterile distilled water and adjusted to 10 6 CFU/mL. Then 10 mL of this suspension was aspirated from the tip of the endoscope through a suction channel; 20 mL was used for the colonoscope.Background: Glutaraldehyde (GA) is currently considered to be the best disinfectant for endoscope disinfection. However, GA poses high risks for medical staff involved in the process and also to the environment. Strongly acidic electrolyzed water (SAEW) has been recently re-evaluated for its potent bactericidal effect and environmental safety. Methods: Through the aspiration channel of the scopes, upper GI endoscopes and colonoscopes were experimentally contaminated with Pseudomonas aeruginosa, Mycobacterium avium and hepatitis B surface antigen positive blood. Four disinfection methods were tested: manual washing only, soaking in 3% GA for 5 and 10 min, and a 10-s soak in SAEW with 50 or 100 mL of aspiration. Results: Direct plating culture was positive for Pseudomononas contamination after manual washing only (1/5) and after a 5-min soak in 3% GA. Complete disinfection, confirmed by enrichment culture and polymerase chain reaction (PCR) of Pseudomonas and hepatitis B surface antigen positive blood on the contaminated upper GI endoscope was obtained after a 10-min soak in GA and after using SAEW (0/5). Mycobacterum avium are rather resistant against SAEW as determined by broth culture and PCR (1/5). Conclusion: Strongly acidic electrolyzed water is a valuable disinfectant for endoscopes.