Different genes govern Yersinia pestis pathogenicity in Caenorhabditis elegans and human lice.

To assess the role of virulence factors identified in Caenorhabditis elegans in the transmission of plague by lice, we infected 100 lice by feeding them on rabbits and made them bacteremic; the rabbits had been intravenously inoculated with 10(9) CFU of six different mutant Yersinia pestis strains of lower pathogenicity for C. elegans, obtained from the KIM5 strain. This strain lacks genes used for biofilm formation. High mortality rates were observed in all lice, which excreted viable bacteria in their feces. Mutants killed rabbits when infected intravenously, but mutants were not transmitted to rabbits by infected lice. We conclude that the genes governing pathogenicity in C. elegans and louse are not identical.