Fowl cholera: gel diffusion precipitin test for serotyping Pasteruella multocida from avian species.

SUMMARY Heat-stable antigens extracted with formalinized saline were used in the gel diffusion precipitin test to group Pasteurella multocida associated with fowl cholera into 5 serotypes. Of 258 field isolants tested, 33 were type 1, 157 were type 3, 28 were type 4, 4 were type 5, and 4 were type 6; 27 isolants reacted with type 3 antiserum and to a lesser extent with type 4 antiserum, and 5 isolants did not react with any antisera. Bacterins prepared with P. multocida serotypes 1, 3, and 4 induced good immunity in chickens and turkeys against organisms of the same serotype. A bacterin prepared with serotype 4 culture induced as good immunity against a serotype 5 challenge-exposure culture as was induced with the homologous bacterin. The serological behavior of the heat-stable antigens was compared by gel diffusion and immunoelectrophoresis with partially purified lipopolysaccharide-protein complex (endotoxin) that had induced specific immunity in turkeys. Lines of identity were observed in the gel diffusion test, but a slight difference was observed with immunoelectrophoresis. The heat-stable antigen was demonstrated in the serum of a turkey with acute fowl cholera and in the blood of turkeys that died of the acute disease.