Laboratory trials with inactivated vaccines against Escherichia coli (O78 K80) infection in fowls.

Laboratory trials made with five inactivated (O78 K80) Escherichia coli vaccines showed that the greatest degree of protection against an intramuscular challenge with the homologous strain was obtained with an alum precipitated vaccine. This vaccine was equally effective when administered by the subcutaneous, intramuscular or intraperitoneal route. Maximal protection, persisting for at least six weeks, was obtained by inoculating chicks at three weeks of age with a dose of approximately 1-5 X 10(9) cells in 0.5 ml. Some degree of protection was obtained, however, in chicks vaccinated earlier. There was no evidence that this vaccine provided any cross protection against other pathogenic serotypes of E coli. No adverse effect was noted on growth rate or carcase quality in the chicks vaccinated. Immunological studies showed that protection was not related to the production of O and K serum agglutinins.