The Influence of Streptomycin on the Ecology of the Intestine and Resistance to Infection

Abstract

Streptomycin administration increased the susceptibility of Swiss white mice to intestinal colonization with Pseudomonas aeruginosa and Salmonella typhimurium and facilitated translocation of these organisms extraintestinally. The antibiotic altered the composition of the mouse cecal flora, caused an increase in the pH and Eh of cecal contents and a decrease in the concentration of volatile fatty acids. In addition, the passage of contents was slower through the cecum of antibiotic treated than untreated animals. P. aeruginosa failed to multiply, under anaerobic conditions, in cecal contents from treated (T) or untreated (U) animals. A population decline was apparent in contents from untreated animals. S. typhimurium multiplied in contents from both groups of animals but its multiplication rate and total population were greater in contents from treated animals. P. aeruginosa multiplied in T-VFA broth, containing concentrations of volatile fatty acids detected in cecal contents of streptomycin treated mice, but failed to multiply in U-VFA broth, which contained acids in concentrations found in untreated mice. S. typhimurium multiplied in both types of broth but its multiplication rate and total population were greater in T-VFA broth than in U-VFA broth.