Abstract
Following the discovery of atypical mycobacterial contamination of endoscopes and of automatic endoscope washers, we report the results of our further investigation. Such contamination had been prevalent when 1% glutaraldehyde solution was used as disinfectant solution, and despite standard use 2% glutaraldehyde solution for the washers when used without exchange of the solution in the washer-reservoir tank for more than two weeks. It is interesting to note that recorded glutaraldehyde concentrations contained in the washer were found to marginally decrease in each washing cycle with a total eventual decrease of 20%-40% by 25 cycles, due to introduction of rinsing water into the disinfect ant reservoir. Optimal concentration of glutaraldehyde (2%) was found to be maintainable using a 3% solution of glutaraldehyde to prevent the washing solution falling below effective concentration levels and by replacing this with a complete exhange twice a week (every 3-4 days). Vigorous brushing of the biopsy channel and overnight immersion of the endoscope, both using concentrated disinfectant solution (3%), effectively prevented atypical mycobacterial contamination. All bacteriological examinations showed that these prevention techniques have been effective for a continuous period of over 18 months to date. We have accordingly undertaken routine examinations of the employed bronchoscopes, following bronchoscopy in 12 cases of active pulmonary tuberculosis where bronchial secretes carried M. tuberculosis, and no contamination of either endoscope or washer by M. tuberculosis was found since introduction of our new techniques. The acid fast bacilli which had contaminated the endoscopes and the washers were confirmed to be M, chelonae subsp. chelonae, M, chelonae subsp. abscessus and M. gordonae. The M. gordonae was also confirmed in the local water delivery systems. The source(s) of other acid fast bacilli are being still actively investigated.
