Resistance to and killing by the sporicidal microbicide peracetic acid.

ABSTRACT

OBJECTIVES: To elucidate the mechanisms of spore resistance to and killing by the oxidizing microbicide peracetic acid (PAA). METHODS: Mutants of Bacillus subtilis lacking specific spore structures were used to identify resistance properties in spores and to understand the mechanism of action of PAA. We also assessed the effect of PAA treatment on a number of spore properties including heat tolerance, membrane integrity and germination. RESULTS: The spore coat is essential for spore PAA resistance as spores with defective coats were greatly sensitized to PAA treatment. Small acid-soluble spore proteins apparently provide no protection against PAA. Defects in spore germination, specifically in germination via the GerB and GerK but not the GerA germination receptors, as well as leakage of internal components suggest that PAA is active at the spore inner membrane. It is therefore likely that the inner membrane is the major site of PAA's sporicidal activity. CONCLUSIONS: PAA treatment targets the spore membrane, with some of its activity directed specifically against the GerB and GerK germination receptors.