COAGGLUTINATION TEST FOR SEROTYPING PASTEURELLA-HAEMOLYTICA

A coagglutination test was described for simple, fast, and reliable de tection of Pasteurella haemolytica type-specific antigens in lung lesi ons even in the absence of viable P. haemolytica. The coagglutinating reagents were prepared by coating protein A-producing Staphylococcus a ureus cells with hyperimmune sera raised against P. haemolytica type s trains. Bacterial suspensions, saline extracts, and boiled saline extr acts of the bacteria were used as antigens. Homologous reactions with all types of antigens were precise. Some cross-reactions were similar to those obtained by the indirect hemagglutination test, and some addi tional one-way cross-reactions were identified. The coagglutination te st was used for serotyping 65 P. haemolytica field strains and for the detection of P. haemolytica type-specific antigens in the lung specim ens of 62 calves and 78 sheep. Ninety-four percent of the field strain s could be serotyped by the coagglutination test. P. haemolytica type- specific antigens were detected in the lung specimens of 3 calves and 5 sheep that had succumbed to naturally occurring P. haemolytica pneum onia and in the lungs of 20 calves experimentally infected with P. hae molytica A1. The coagglutination test detected type-specific antigens in 36% of the lung specimens of slaughtered field sheep but not in the lungs of slaughtered field cattle with small chronic lung lesions. No reaction occurred in the case of nonpneumonic calves and sheep or whe n pneumonic lesions were caused by other bacteria. No P. haemolytica s trains could be isolated from lung samples that were coagglutination t est negative. This test is recommended as an additional method for fas t and reliable serotyping of P. haemolytica.