Pathogenicity of conventional and debilitated Escherichia coli K12

Abstract

THE development of ‘disabled’ strains of Escherichia coli for recombinant DNA work has so far concentrated on abolishing their ability to survive outside the test tube and to persist in the intestinal tract of man and animals. However, these changes make it impossible to test for any possible changes in pathogenicity in these strains caused by inserted foreign DNA by simple oral inoculation. Oral inoculation also does not provide any information on their relative pathogenicity if accidentally introduced by any other route. We have therefore investigated the ability of E. coli K12 DO-11 and of the ‘disabled’ E. coli χ1776 to colonise and kill susceptible mice when introduced by various parenteral routes. We show that at high concentrations both of these E. coli strains, which do not colonise the intestines of normal (non-germ-free) mice, can survive and prove lethal when injected intravenously, intraperitoneally or intracranially.