Studies on the antigenic relationships of six adherent isolates of Bordetella bronchiseptica

Six isolates of Bordetella bronchiseptica recovered from swine with atrophic rhinitis were studied. All hemagglutinated swine red blood cells, autoagglutinated in saline and showed fimbriae by electron microscopy. Hyperimmune sera against each were produced in rabbits and the antigenic relationships between the isolates were studied by cross-absorption and by the determination of the cross-reactivity indices of pairs of sera. Three isolates seemed to be identical by both methods, while 2 others showed close antigenic relationships. Hemagglutination titers with heterologous antigens and cross-reactivity indices greater than 0 suggest some degree of cross-immunity among the isolates studied, even when antigenic heterogeneity was demonstrated.