Efficacy of hospital cleaning agents and germicides against epidemic Clostridium difficile strains

Objective. To compare the effects of hospital cleaning agents and germicides on the survival of epidemic Clostridium difficile strains. Methods. We compared the activity of and effects of exposure to 5 cleaning agents and/or germicides (3 containing chlorine, 1 containing only detergent, and 1 containing hydrogen peroxide) on vegetative and spore forms of epidemic and non-epidemic C. difficile strains (3 of each). We carried out in vitro exposure experiments using a human fecal emulsion to mimic conditions found in situ. Results. Cleaning agent and germicide exposure experiments yielded very different results for C. difficile vegetative cells, compared with those for spores. Working-strength concentrations of all of the agents inhibited the growth of C. difficile in culture. However, when used at recommended working concentrations, only chlorine-based germicides were able to inactivate C. difficile spores. C. difficile epidemic strains had a greater sporulation rate than nonepidemic strains. The mean sporulation rate, expressed as the proportion of a cell population that is in spore form, was 13% for all strains not exposed to any cleaning agent or germicide, and it was significantly increased by exposure to cleaning agents or germicides containing detergent alone (34%), a combination of detergent and hypochlorite (24%), or hydrogen peroxide (33%). By contrast, the mean sporulation rate did not change substantially after exposure to germicides containing either a combination of detergent and dichloroisocyanurate (9%) or dichloroisocyanurate alone (15%). Conclusions. These results highlight differences in the activity of cleaning agents and germicides against C. difficile spores and the potential for some of these products to promote sporulation.