Background: Cleaning and disinfection procedures play an essential role in the prevention of infection transmission in gastrointestinal endoscopy. In spite of published detailed guidelines, several variants and weak points still exist.

Methods: Cleaning-disinfection procedures were carried out according to “Working Party, Sydney 1990.” A microbiologic surveillance protocol tested the contamination of endoscopes and of automatic washing machines. To assess and improve the efficacy of disinfection, we adopted a quality assurance program.

Results: During a 2-year follow-up, the outside surfaces of gastroscopes were contaminated in 60.5% and channels in 41.3%; the outside areas of colonoscopes were contaminated in 62.3% and channels in 40.3%. Isolated bacteria were gram-negative organisms, particularly Pseudomonas species, and gram-positive organisms, mostly Staphylococcus species. The water reservoirs of automatic washing machines were frequently contaminated by Pseudomonas aeruginosa . The disinfection of washing machines and alcohol rinsing of endoscopes after standard procedures significantly reduced the bacterial contamination.

Conclusions: The microbiologic surveillance pointed out the main weak points that could be improved by the adoption of corrective interventions. Quality assurance is a feasible method to assess the efficacy of cleaning-disinfection, and its wide application would improve quality of care. (Gastrointest Endosc 1996;43:457-62.)