[An index of the activity of antiseptics]

A new parameter is suggested: the antiseptic activity index (AAI), representing a ratio of the antiseptic concentration recommended for practice to its minimal suppressing concentration (MSC) for a certain bacterial strain or X + 2S MSC (the mean arithmetic value with two sigmas) for a population, species, or group of closely related species. This index has been determined in extrahospital and hospital strains of Staphylococcus aureus (342 strains), Pseudomonas aeruginosa (277 strains), and Enterobacteriaceae (500 strains). AAI gives a quantitative characterization of the antiseptic activity and of bacterial sensitivity to antiseptics, it is recommended for practical therapeutic and prophylactic antiseptics.