Abstract
The serological relationships of 47 strains derived from the genera Achromobacter, Acinetobacter, Alcaligenes, Mima, Herellea, Moraxella, Neisseria, Flavobacterium, Cytophaga and Agrobacterium were examined in gel diffusion studies using ultrasonically disintegrated bacterial suspensions as antigens and antisera raised against these in rabbits. The results of cross precipitation tests were coded for computer analysis by three different methods: qualitative, 2-state quantitative and multistate quantitative. The qualitative method of coding was found unsatisfactory as only 22 of 47 strains were grouped at a similarity level of 80 per cent. The 2-state and multistate quantitative methods resulted in satisfactory classifications which, however, were not identical; nevertheless it was shown that most discrepancies in the dendrograms could be resolved by examining the mean similarities between groups of strains. The homologous precipitation patterns of 20 of the 47 strains used in the preliminary experiments were examined in detail and 128 different precipitation lines were identified and numbered. The antigenic structure of the 20 reference strains and a further group of strains were then defined in terms of the 128 numbered precipitation lines and the resultant table of data was numerically analysed presenting the strains as objects and the presence or absence of the 128 precipitation lines in each strain as tests and vice versa; that is, presenting the 128 precipitation lines as objects and their presence or absence in the strains as tests. The following well defined groups appeared in all computations: 1. Oxidase-positive Moraxella strains, Neisseria caviae and N. catarrhalis with precipitation lines 6 and 8 common to all strains; 2. Mima polymorpha, Herellea vaginicola, Acinetobacter anitratum, Acinetobacter lwoffii and non-motile Achromobacter strains based on sharing precipitation lines 13, 14, 20, 21, 35, 36, 40, 41 and others. 3. Alcaligenes strains, motile Achromobacter strains and Mima polymorpha var. oxidans, based on sharing precipitation lines 89 and 31. Computer analysis of serological relationships of loosely bound or superficially situated antigens on the cell revealed by agglutination tests did not show any correspondences with the groupings obtained by cross reactions of antigens released by ultrasonication.