Modulating Effect of Subinhibitory Concentrations of Compound LY 127935 on the Virulence of <i>Escherichia col</i><i>i</i> in the Mouse

Abstract

The filamentous forms of a serum resistant Escherichia coli strain developed under in vitro exposure to subminimal inhibitory concentration of the compound LY 127935 showed a higher resistance against host defence than the nontreated control bacteria. Significantly diminished LD₅₀ values and a longer lasting persistence in the peritoneal cavity of the mouse were found after intraperitoneal infection. In order to exclude the suggestion that the enhanced virulence was only due to the separation of filaments into normal virulent bacilli, the course of experimental infection with normal virulent germs was investigated under treatment with subtherapeutic doses of the antibiotic. When animals treated with repeated doses of 10–15 μg/kg of LY 127935 were intraperitoneally infected a significantly smaller elimination rate of bacteria was observed in the peritoneal cavity than in animals injected with saline.