Abstract
Strains of Escherichia coli causing urinary-tract infections were found to be more commonly haemolytic than were faecal strains. Strains from the introitus that subsequently gave rise to urinary-tract infections resembled urinary strains and those that did not give rise to infections resembled faecal strains. alpha-Haemolysin production was closely associated, in strains from a variety of different sources, with the production of a haemolysin detectable in liquid medium and with cytotoxicity in tissue culture.