Sporicidal activity of chemical sterilants used in hospitals

The current study was designed to assess the sporicidal activity of chemical sterilants using the Association of Official Analytical Chemists (AOAC) sporicidal test. Chemical sterilants are used most commonly in the healthcare setting to disinfect medical instruments such as endoscopes. This study was undertaken to evaluate the efficacy of several newer formulations of glutaraldehydes and hydrogen peroxide as chemical sterilants.

Using the AOAC test the following agents were tested: two 2% alkaline glutaraldehydes (2% Alk-Glut), 2% acid glutaraldehyde (2% Acid Glut), 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate, 10% glutaraldehyde-0.5% phenylphenol-0.1% tertiary amylphenol, and 6% hydrogen peroxide (H2O2). Growth in > 1 of 60 seeded penicylinders is considered by the AOAC to indicate failure of sporicidal activity.

Test results of the six disinfectants against Bacillus subtilis using the manufacturers' specified use-dilution and exposure time were: 0/60 with 2% Alk-Glut (product 1) at 10 hours, 0/60 with 2% Alk-Glut (product 2) at 8 hours, 0/60 with 2% Acid Glut at 10 hours, 2/60 with 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate at 6.75 hours, 0/60 with a 1:5 dilution (2.0% Glut) of 10% glutaraldehyde-0.5% phenylphenol-0.1% amylphenol at 6 hours, 59/60 with a 1:20 dilution (0.5% Glut) of 10% glutaraldehyde-0.5% phenylphenol-0.1% tertiary amylphenol at 12 hours and 0/60 with 6% H2O2 at 6 hours. Test results against Clostridium sporogenes were: 2/60 with 2% Alk-Glut (product 1) at 10 hours, 1/60 with 2% Alk-Glut (product 2) at 8 hours, 1/60 with 2% Acid Glut at 10 hours, 2/60 with undiluted 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate at 6.75 hours, 6/60 with a 1:5 dilution (2% Glut) of 10% glutaraldehyde-0.5% phenylphenol-0.1% amylpenol at 6 hours, 60/60 with a 1:20 dilution (0.5% Glut) of 10% glutaraldehyde-0.5% phenylphenol-0.1% amylpenol at 12 hours, and 0/60 with 6% H2O2 at 6 hours. Dilutions of 2% glutaraldehyde-7.05% phenol-1.20% sodium phenate yielded the following results against C sporogenes: 59/60 with a 1:8 dilution (0.25% Glut) at 6.75 hours, 60/60 with a 1:16 dilution (0.125% Glut) at 6.75 hours, 11/90 with a 1:8 (0.25% Glut) dilution at 12 hours, and 60/60 with a 1:16 dilution (0.125% Glut) at 12 hours.

Both 2% acid and alkaline glutaraldehydes are effective chemical sterilants. Diluting glutaraldehyde-based sterilants below 2% glutaraldehyde resulted in failure to kill spores of B subtilis and C sporogenes.