EFFICACY OF VARIOUS DISINFECTANTS IN KILLING A RESISTANT STRAIN OF PSEUDOMONAS-AERUGINOSA BY COMPARING ZONES OF INHIBITION - IMPLICATIONS FOR ENDOSCOPIC EQUIPMENT REPROCESSING

Objective: Previous studies have shown that high-level disinfection of GI endoscopes may not be reliably achieved using glutaraldehyde at ro om temperature. In our laboratory, we have isolated a strain of Pseudo monas aeruginosa that is resistant to disinfection with glutaraldehyde . We compared the bactericidal activity of various disinfectants again st this organism. Methods: One hundred microliters of an overnight cul ture of this organism was spread onto blood agar plates. Twenty microl iters of a disinfectant was placed on a sterile 7-mm filter paper, pla ced on the blood agar plate, and incubated overnight at 37 degrees C t o determine the zone of inhibition for each disinfectant tested. Disin fectants included Cider, Dispatch, Virahol, OMNI II, Lysol, IodoFive, Lysol I.C. Spray, and Chlorox. The zone of inhibition (i.e., clearing) roughly correlates with the bactericidal strength of the disinfectant . Results: Compared with the glutaraldehyde-containing solution Cider, the alcohol-containing disinfectants Lysol I.C. Spray and Virahol had the largest mean zones of inhibition (11.33 vs 20.60 and 20.55 mm; p = 0.0001). The hypochlorite compounds Chlorox (1:10 dilution) and Disp atch had mean zones of inhibition similar to that of Cider (11.08 and 11.25 mm vs 11.33 mm; p = not significant). The phenolic compounds OMN I II and Lysol had mean zones of inhibition smaller than that of Cider (10.50 and 10.35 mm vs 11.33 mm; p < 0.006), and the phosphoric acid and iodine-containing IodoFive had the smallest mean zone of inhibitio n (9.70 vs 11.33 mm; p = 0.0001). Conclusion: The alcohol-containing d isinfectants had the largest zones of inhibition against resistant P. aeruginosa. These compounds may be more effective than glutaraldehyde for endoscopic equipment reprocessing. (C) 1998 by Am. Coll. of Gastro enterology.