Production of colicin V in vitro and in vivo and observations on its effects in experimental animals

Abstract

In recent years, a possible relationship between pathogenicity and colicinogeny in some Escherichia coli strains responsible for gastrointestinal infection and bacteremia in man and animals has been inferred. Using enterotoxigen-negative, colicin V-producing E. coli strains, we have (i) elaborated a simple in vitro method for producing greater yields of colicin V free of bacterial cells and large, non-dialyzable molecules; (ii) detected the presence of the bacteriocin in peritoneal fluids of moribund mice injected intraperitoneally 18 h previously with colicin V-producing strains (in these mice, Col V+ exconjugants survived and multiplied more extensively than the Col V- recipient strains from which they were derived; and (iii) observed an increased vascular permeability and inflammatory response in rabbits and guinea pigs when a culture supernatant demonstrating colicin activity was injected intradermally. The vascular response obtained after the injection of either a colicin V-containing dialysate alone or that of a trypsinized colicin-containing supernatant was always smaller than when the colicin V-active supernatant was injected. An enterotoxin-free dialysate containing colicin V also increased markedly in rabbits and guinea pigs the mild inflammatory reaction that occurred in the skin when purified endotoxin was injected subcutaneously in microgram doses. Our results are consistent with the hypothesis that colicin V may act as a virulence factor in some E. coli strains.