Sporicidal activity of disinfectants as one possible cause for bacteria in patient-ready endoscopes.

Four endoscopes were cleaned by an experienced endoscopy technician using an enzyme detergent solution with brushing, rinsing with tap water, and then high-level disinfection in an automatic endoscope reprocessing machine using CIDEX orthophthalaldehyde solution (CIDEX OPA). After disinfection, the channels of these patient-ready endoscopes were flushed with sterile neutralizing medium, brushed with a sterile brush, and then flushed again with sterile medium. The effluent from each flush was collected in sterile bottles, immediately returned on ice to a laboratory, and tested for the presence of bacteria. An average of about 200 colony-forming units of bacteria were recovered from each endoscope. Upon staining and microscopic examination, 3 of these colonies were spore-forming bacteria, and 7 colonies were nonspore-forming bacteria. These results suggest that the endoscopes might have been contaminated with a biofilm. Bacterial biofilms have been speculated to commonly occur in endoscopes as a result of the many possible inadequacies of cleaning, disinfecting, rinsing, drying, storage, and other functions associated with the difficulties of reprocessing endoscopes. As one possible cause for a biofilm, three high-level disinfectants (CIDEX activated dialdehyde solution, CIDEX OPA, and Aldahol high-level disinfectant) were tested for their sporicidal activity against high-protein or low-protein cultures of spore-forming bacteria in suspension. The potential importance of killing spore-forming bacteria within a practical exposure time in order to prevent the formation of biofilms is discussed.

The influence of laboratory adaptation on test strains, such as Pseudomonas aeruginosa, in the evaluation of the antimicrobial efficacy of ortho-phthalaldehyde.

The microbiocidal efficacy of 0.55% ortho-pthalaldehyde (OPA) was evaluated in a rough carrier test, using more than 200 strains of bacteria and yeasts from patients and reference ATCC strains. This test was then compared with the European carrier test (prEN14561) using Pseudomonas aeruginosa. We also sought to determine whether recently isolated P. aeruginosa had the same susceptibility to OPA, after laboratory adaptation. It was shown that P. aeruginosa was less susceptible to OPA (being reduced by a factor of 10(3.8)) than the other strains (reduced by a factor of 10(4)). The surface test used, produced a lesser reduction of P. aeruginosa than the European test. For recently isolated strains (N = 66), the rough model demonstrated that the number of survivors increased both quantitatively and qualitatively from day one to day seven. It was concluded that disinfectant efficacy should be confirmed with recently isolated organisms.

In-hospital evaluation of orthophthalaldehyde as a high level disinfectant for flexible endoscopes.

One hundred endoscopes used for bronchoscopy (30), gastroscopy (35) or colonoscopy (35) were studied to determine the efficiency of a new high level disinfectant, orthophthalaldehyde (OPA). Manual cleaning was the method studied since this would be the least effective and thereby provide the greatest challenge to the 0.5% (w/v) OPA solution. The OPA was convenient and easy to use since it did not have irritating vapours and as it is used directly, does not require dilution. Our study demonstrated that the OPA was stable for up to 14 days despite repeated re-use. The cleaning/disinfection procedure could achieve a > or = 5 LOG10 reduction in bacterial load. This in-hospital evaluation supports the conclusion that OPA is an effective choice as a high level disinfectant for flexible endoscopes.