Modes of action of three disinfectant active substances: A review

This review deals with three categories of active substances for disinfectant products, their modes of action (MOA), and how MOA can help predict propensity for resistance in microorganisms. Within the European Union applications for approval of disinfectants of all kinds must be submitted in a few years, and documentation on MOA and resistance must be part of those applications. Peracetic acid is an unspecific, pervasive oxidizer of C-C double bonds and reduced atoms. This MOA would imply poor chance for development of resistance in microorganisms, as borne out by the absence of such reports in the literature. The quaternary ammonium compounds (QAC's) are much more specific in their antimicrobial mechanism. Even very low concentrations cause damage to the cytoplasmic membrane due to perturbation of the bilayers by the molecules' alkyl chains. Development of microbial resistance to QAC's, as well as cross-resistance to antibiotics, are particularly well documented. The polymer PHMB is antimicrobial because it disturbs the cell membrane's bilayer by interacting with it along the surface of the membrane. Resistance to the polymer appears not to develop despite many years of use in many fields. However, PHMB's toxicity to humans upon inhalation dictates great caution when deploying the substance.