OBSERVATIONS ON QUATERNARY AMMONIUM DISINFECTANTS

Abstract

Bacterial death rate studies were carried out with several quaternary ammonium compounds. The survivor curves were found to be sigmoid. This shape was shown to be due to the difference in resistance to the QAC among the individual cells. An exponential rate was found when a more resistant strain was selected from the survivors of disinfection. Sporocidal action was not found. The reaction between substrate protein and the QAC removes the disinfectant from solution and occurs in the presence of a wide QAC–protein ratio, but the bactericidal action is dependent upon the concentration of the disinfectant. Serratia marcescens was adapted to grow in 200 times the originally lethal concentration of disinfectant, Escherichia coli in 43 times, but no increase in concentration was tolerated by Micrococcus pyogenes var. aureus.