title: alpha-Haemolysin: an additive virulence factor in Escherichia coli.
abstract: Haemolytic Escherichia coli, including human intestinal and extraintestinal as well as porcine enterotoxigenic and oedema disease isolates, and Proteus morganii strains were studied for their virulence. Hly+ wild type strains and Hly+ transconjugants were more virulent than Hly- derivatives as shown in mice and chick embryos. This enhanced virulence seems to be connected with the ability of diffusible alpha-haemolysin production because clones producing only non-diffusible, beta-haemolysin behaved as non-haemolytic ones. Haemorrhagic lung symptoms and haemoglobinuria were frequently observed after parenteral challenge of mice with alpha-haemolytic clones. Though the Hly- clone exhibited a high resistance against blood clearance, the number of circulating bacteria was significantly higher in the case of alpha-haemolytic clone. A causal connection between this phenomenon and the leukocidin activity of alpha-haemolysin is suggested.
mesh_terms: D000818:Animals; D002642:Chick Embryo; D004926:Escherichia coli / Q000378:metabolism / Q000472:pathogenicity*; D006459:Hemolysin Factors; D006460:Hemolysin Proteins / Q000096:biosynthesis / Q000502:physiology*; D007956:Leukocidins; D051379:Mice; D011511:Proteus / Q000472:pathogenicity; D011654:Pulmonary Edema / Q000209:etiology
chemical_list: D006460:Hemolysin Proteins; D007956:Leukocidins