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Mycobacteria and glutaraldehyde: is high-level disinfection of endoscopes possible?
S Urayama1, R A Kozarek, S Sumida
1Department of Internal Medicine, Virginia Mason Medical Center, Seattle, Washington 98111, USA.
Background:
High-level disinfection of endoscopes has traditionally been undertaken by manual or automatic scope cleaning plus a 10 to 20 minute soak in 2% alkaline glutaraldehyde. Mycobacteria species are less sensitive to glutaraldehyde, and a 45-minute instrument soak has recently been recommended by the manufacturer. Because of concerns over endoscope damage, need for more endoscopes, and perception that the current cleaning method is adequate, we prospectively studied mycobacteria-contaminated endoscopes at various stages of the cleaning process.
Methods:
All work was done under a laminar flow hood in a microbiology laboratory. Five gastrointestinal scopes were contaminated with 10(8) colony forming units per milliliter (CFU/mL) of Mycobacterium chelonei, an atypical mycobacterium similar in chemical resistance to Mycobacterium tuberculosis but with less infectious potential. Cultures of the sheath, biopsy channel, and elevator channel were taken at baseline, after manual cleaning, and after 10, 20, and 45 minutes to glutaraldehyde soak both before and after alcohol rinse.
Results:
Manual cleaning resulted in a mean of 4.7 log10 reduction in viable mycobacterial colonies. Qualitative studies of the external endoscope surface as well as the air-water valve showed no detectable organisms after a 10-minute exposure to alkaline glutaraldehyde. Conventional quantitative culture techniques of the channels demonstrated one endoscope out of five with consistent growth after a 10-minute exposure to glutaraldehyde. Following alcohol treatment, there was no significant colony growth. In contrast, a quantitative membrane filter system showed the presence of at least one mycobacterial colony in four out of five scopes after a 45-minute glutaraldehyde exposure.
Conclusions:
Additional studies utilizing a standardized mycobacterial species, inoculum size, and suspension characteristics are recommended to delineate adequate duration of disinfectant exposure time.
Insights
Standard endoscope disinfection may not eliminate mycobacteria. A 45-minute glutaraldehyde soak was less effective than expected, indicating a need for further research on optimal disinfection protocols for medical scopes.
Area of Science:
- Microbiology
- Infectious Diseases
- Healthcare Disinfection
Background:
- Traditional endoscope disinfection involves manual cleaning and a 10-20 minute glutaraldehyde soak.
- Mycobacteria require longer glutaraldehyde exposure (45 minutes recommended) due to resistance.
- Concerns exist regarding endoscope damage and the adequacy of current cleaning methods.
Purpose of the Study:
- To prospectively evaluate the efficacy of glutaraldehyde disinfection against mycobacteria-contaminated endoscopes.
- To assess mycobacterial reduction at various stages of the cleaning and disinfection process.
Main Methods:
- Five gastrointestinal scopes were contaminated with Mycobacterium chelonei.
- Cultures were taken after manual cleaning and glutaraldehyde soaks (10, 20, 45 minutes) with and without alcohol rinse.
- Both conventional culture and a quantitative membrane filter system were used.
Main Results:
- Manual cleaning reduced mycobacteria by 4.7 log10.
- 10-minute glutaraldehyde soak eliminated detectable external organisms but not always internal ones.
- A 45-minute soak detected mycobacteria in 4/5 scopes using a sensitive filter method, contrasting with conventional cultures.
- Alcohol rinse following glutaraldehyde soak showed no significant growth.
Conclusions:
- Current disinfection protocols may be insufficient for complete mycobacterial eradication.
- Further studies are needed to establish standardized methods for determining adequate glutaraldehyde exposure times.
- Optimizing disinfection protocols is crucial for preventing healthcare-associated infections.