Observations Concerning the Pathogenesis of E. Coli Infections in Mice

Summary Two strains of E. coli, serotypes 07 and 0111, which had been found to differ strikingly in their ability to kill mice after intraperitoneal inoculation were compared in order to define certain aspects of the pathogenesis of E. coli infections. Bacteriolytic, bactericidal and opsonizing capacity of 07 antisera was strikingly less for 07 than 0111 antiserum was for 0111, despite the fact that homologous antisera contained comparable quantities of agglutinating antibody for the two organisms. The more virulent organism, 07, resisted phagocytosis by macrophages in vivo and by polymorphonuclear leukocytes in vitro; in addition it persisted intraperitoneally and multiplied. Thus these studies define an important role for phagocytosis in the pathogenesis of virulent E. coli infections.