Immunological Relationships of Encapsulated Gram-Negative Rods. ∗

The difficulties encountered in the past, in the differentiation of the bacteria exemplified by the organisms of Friedlander, rhinoscleroma, ozaena, granuloma inguinale and Bad. aero genes, have more recently been increased, rather than diminished, by the discovery that members of the different species possess common immunological characteristics by virtue of similarities in the capsular carbohydrate. 1 Studies on the immunological reactions of the unencapsulated cell 2 supplied the hypothesis that the different organisms, once deprived of the ability to elaborate capsular polysaccharide, might be more readily amenable to systematization. Accordingly, unencapsulated, or “R”, strains have been derived from the encapsulated “S” strains by continued cultivation of the ”S“ form in homologous anti-S serum. Usually, 6 to 12 transplants in broth containing 10% immune serum sufficed for the conversion. Rabbits were then injected intravenously with suspensions of heat-killed (30 min. at 56°C.) R forms until the sera contained sufficient antibody for serological study.

For this purpose, anti-sera were obtained with R cells derived from Friedlander's bacillus, Types A and B and Group X; ozaena bacillus, Types I and II and Group III; three immunologically different strains of Bact. aerogenes; and a single strain of rhinoscleroma and granuloma bacillus. Agglutinations were then conducted employing each R strain and each anti-serum. In order to illustrate the reactions observed, a summary protocol has been arranged of all the reactions. The titres of the different anti-sera were close to 1:5000, and the agglutination was composed of large, coarse granules readily disrupted on agitation. This is, of course, in contradistinction to the agglutination of S cells, which is characterized by a compact, tenacious disc. Examination of the data reveals 2 large groups disclosed by the agglutination reaction.