Natural bioburden levels detected on flexible gastrointestinal endoscopes after clinical use and manual cleaning.

BACKGROUND: Colonoscopes present a special bacterial decontamination challenge because the colon has a large and diverse microbial population.

METHODS: Bioburden of colonoscope insertion tube surfaces and suction channels were determined after use and after manual cleaning.

RESULTS: After use bioburden in suction channels averaged 7.0 x 10(9) colony-forming units (cfu). Cleaning reduced this level to 1.3 x 10(5). Cleaning of tube surfaces reduced the after-use bioburden from a level of 5.1 x 10(5) to 2.2 x 10(4) cfu. Gram-negative rods accounted for approximately 99% of the bioburden within the suction channel after use and after cleaning. After use flora were predominantly Escherichia coli and Bacteroides. The flora shifted to waterborne Pseudomonas organisms, and other members of the family Enterobacteriaceae after cleaning. Gram-positive bacteria were the primary isolates from the device surfaces both after use (56%) and after cleaning (47%). Because gram-positive cocci and diphtheroids are a part of the normal microbiota of the skin, these bacteria may have been introduced by the hospital environment or by handling.

CONCLUSIONS: After the cleaning of in-use colonoscopes, fewer than 10(6) vegetative bacteria could be recovered. This value is several logs lower than some previous estimates. This finding may be useful in the formulation of sterilization and disinfection cycles. Microflora from the colonoscopes indicated that the cleaning process introduced waterborne and enteric microorganisms, which highlights the importance of sanitation in the device reprocessing area.