Antigenic relationships of Haemophilus pertussis, the parapertussis bacillus, and Brucella bronchiseptica as shown by cross protection tests in mice.

Antigenic relationships among the three organisms, Haemophilu-s pertussi8, the parapertussis bacillus, and Brucella bronchiseptica, have been demonstrated by various workers, using different methods. Ferry and Noble (1918), by means of agglutination tests, and Ferry and Klix (1918), using complement fixation procedures, showed cross reactions between H. pertussis and B. bronchiseptica. In connection with the description of the parapertussis bacillus Eldering and Kendrick (1938) outlined the differential characteristics and demonstrated relationships with H. pertusis and B. bronchiseptica using agglutination and agglutinin absorption techniques. Evans (1940) studied the toxins of the three organisms and showed that they were aRl neutralized by pertussis antitoxic serum. Further evidence of these relationships was presented in the work of Eldering (1942) with protection test in mice challenged by the intraperitoneal route. The results indicated cross protection among the three species. In fect, B. bronchiseptica antigens, either the whole culture or a carbohydrate fraction, protected against H. pertus8is infection fully as well as did H. pertuwsi8 antigen itself. It is of interest that both the parapertussis bacillus and B. bronchiseptica occasionally are found associated with clinical whooping cough in children. A recent paper by Eldering and Kendick (1952) reports that approximately 2 per cent of the cultures isolated in the Grand Rapids area during a 16 year period from children with whooping cough symptoms were parapertussis.