Mechanisms of antimicrobial action of antiseptics and disinfectants: an increasingly important area of investigation

The term ‘biocide’ is increasingly being used to describe compounds with antiseptic, disinfectant or, sometimes, preservative activity. A compound might be used in only one such capacity or possess two or even all of these properties. 1 Until fairly recently, there were two long-held general opinions about biocides. The first was that, as long as they were effective, there was little reason (apart from academic value) to determine how they achieved their inhibitory or lethal effects. The second, widely perceived, view was that antiseptics and disinfectants acted as general protoplasmic poisons and, as such, merited little attention. At the beginning of the twentieth century, there were few drugs available for the treatment of infections. Antiseptics and disinfectants had at that stage been employed for various purposes and in various guises, notable examples being phenol (carbolic acid), mercuric chloride, chlorine, hypochlorites and iodine. Quaternary ammonium compounds (QACs) were described in 1916 but were not used commercially for another 19 years or so. 2 Early studies on the action of such compounds concentrated on the kinetics of bacterial inactivation, 3 although Cooper 4