Mycobacteria and glutaraldehyde: is high-level disinfection of endoscopes possible?
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.
Urayama
S
S
Department of Internal Medicine, Virginia Mason Medical Center, Seattle, Washington 98111, USA.
Kozarek
R A
RA
Sumida
S
S
Raltz
S
S
Merriam
L
L
Pethigal
P
P
D000433:1-Propanol / Q000494:pharmacology; D015169:Colony Count, Microbial; D004203:Disinfection / Q000592:standards*; D020776:Endoscopes, Gastrointestinal; D004866:Equipment Contamination; D005976:Glutaral / Q000494:pharmacology*; D016926:Mycobacterium chelonae / Q000187:drug effects* / Q000302:isolation & purification
D000433:1-Propanol; D005976:Glutaral