Ethanol disinfection of plastic-adherent micro-organisms

This study investigated the bactericidal effect of ethanol/water (70:30 vol:vol) against plastic-adherent organisms that commonly cause line infections. The experiments were performed in polycarbonate wells and all incubations were at 37 degrees C. Bacteria in broth were inoculated into wells and incubated (16, 40 and 72 h) before washing to remove non-adherent organisms and exposure to ethanol/water. Wells were then re-incubated with broth to detect surviving bacteria. All organisms incubated for 16 h were killed by 1h of exposure to 70% ethanol. After incubation for 40 h, 4h of exposure to ethanol was required to kill two strains of Candida albicans. Likewise, one of three of both Klebsiella pneumoniae and Pseudomonas aeruginosa, incubated for 72 h, showed growth after 1h of exposure to 70% ethanol but not after 4h of exposure. These results suggest that in contrast to log phase organisms, which are killed by ethanol/water solutions in seconds, plastic-adherent organisms are more resistant to the bactericidal activity of ethanol.