Inhibition of Shigella flexneri by the Normal Intestinal Flora I. Mechanisms of Inhibition by Klebsiella

Abstract

Growth curves were plotted for Shigella flexneri and Klebsiella ( Aerobacter aerogenes ) multiplying in pure and mixed culture. In mixed culture, Klebsiella inhibited Shigella . Exponential growth was interrupted and Shigella entered into a logarithmic death phase. An analysis of cultures at the time inhibition occurred revealed that formic and acetic acids produced by Klebsiella were responsible for the inhibition of Shigella . Klebsiella strongly reduced the culture medium. The volatile fatty acids, operating under reduced conditions, exerted a bactericidal effect on Shigella . Results are discussed with reference to the possible role of volatile fatty acids as factors responsible for Shigella inhibition in vivo.