Inactivation of Clostridium difficile spores by disinfectants

The current study was designed to evaluate the activity of glutaraldehyde-based disinfectants against Clostridium difficile using the Association of Official Analytical Chemists' (AOAC) sporicidal test. This study was undertaken because gastrointestinal endoscopes that may be contaminated with C difficile spores are most commonly disinfected between patients using glutaraldehyde-based disinfectants.

Using the AOAC test, the following disinfectants were tested: 2% alkaline glutaraldehyde, 2% acid glutaraldehyde, a 1:16 dilution of a 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate, and a 1:20 dilution of a 10% glutaraldehyde-0.5% phenylphenol-0.1% amylphenol.

Test results of the four disinfectants against C difficile spores at exposure times of 10, 20, and 60 minutes were as follows (number of positive penicylinders per 30 replicates): 0, 0, and 0 for 2% alkaline glutaraldehyde; 6, 3, and 0 for 2% acid glutaraldehyde; 30, 29, and 30 for a 1:16 dilution of glutaraldehyde-7.05% phenol-1.20% sodium phenate; and 30, 30, and 30 for a 1:20 dilution of glutaraldehyde-0.5% phenylphenol-0.1% amylphenol.

C difficile spores are more susceptible to inactivation by glutaraldehyde-based disinfectants than the spore-forming organisms recommended in the AOAC sporicidal test (i.e., Bacillus subtilis and Clostridium sporogenes). Diluting glutaraldehyde-based disinfectants below 2% led to the inability to inactivate spores of C difficile using exposure times commonly employed to disinfect semicritical items such as gastrointestinal endoscopes.