Effect of Surface Active Agents on Oxidations of Lactate by Bacteria

Baker, Harrison and Miller 1 have studied the effect of synthetic surface active agents on the metabolism of bacteria as measured in the Warburg manometric apparatus. Cationic surface active agents were found to inhibit equally the metabolism of both Gram positive and Gram negative bacteria. Anionic agents, in general, inhibit the metabolism of Gram positive bacteria only. In a subsequent paper 2 studies on bactericidal effects were reported. Dubos 3 discussed the differential susceptibility of Gram positive and Gram negative bacteria to different injurious agents, and suggested the use of anionic and cationic surface active agents as tools for the study of bacterial structure.

In this paper we report the effects of an anionic surface active agent, the dioctyl ester of sodium sulfosuccinate, and of a cationic agent, cetyl pyridinium chloride, on a Gram positive organism and a Gram negative organism. As an index of the action of these agents we used the oxidation of lactate by molecular oxygen as compared with anaerobic oxidation by methylene blue.

Methods. Two organisms were used, the Insecticide Board strain of Staphylococcus aureus, a Gram positive organism, and Escherichia coli, University of Washington No. 406, a Gram negative organism. These two cultures were selected because they possessed relatively active lactic dehydrogenases as determined by the Thunberg technic.

Staphylococcus aureus was grown on the broth prescribed for the Food and Drug Administration procedure for the phenol coefficient. 4 After 24 hours' incubation, the organisms were collected by means of a continuous flow' Sharpies centrifuge and washed 3 times with M/100 phosphate buffer at pH 7.0. Escherichia coli was grown on Blake bottles containing F. D. A. broth to which 2% agar had been added.