Antimicrobial efficacy of endoscopic disinfection procedures: a controlled, multifactorial investigation

Background: Adequate disinfection of endoscopes is essential to prevent env ironmental and patient-to-patient transmission of infectious agents, but da ta from controlled studies are limited. Moreover, there is controversy rega rding current guidelines for disinfection. We compared the antimicrobial ef ficacy of several endoscopic disinfection procedures controlling for multip le factors that affect reprocessing. Methods: A colonoscope was contaminated with 10(8) CFU/mL of Enterococcus f aecalis as a standardized inoculum. The colonoscope was passed through 1 of 16 study arms (5 reps/arm for a total of 80 runs) that were controlled for all possible combinations of the following variables: manual precleaning; 10-, 20-, or 45-minute glutaraldehyde exposure; air or ethanol drying; or a utomated reprocessing with peracetic acid (liquid sterilization system). Su ction accessory channels and air-water channels were harvested for microbio logic culture. Results: Control runs (no cleaning or disinfection) recovered more than 5 x 10(7) CFU/mL from each sampling site. When each processing variable was is olated independent of other variables, the benefits of manual precleaning, longer soak times, and ethanol drying were apparent. When factors were comb ined, manual precleaning followed by 20- and 45-minute glutaraldehyde expos ure and ethanol drying removed all test organisms, as did processing with t he liquid sterilization system. Conclusion: Although the initial cost is higher, the automated liquid steri lization system provides effective sterilization and minimizes worker expos ure. In units where chemical disinfection is used, our results suggest that manual precleaning followed by at least 20-minute glutaraldehyde exposure and ethanol rinse drying are sufficient to achieve complete disinfection.