Study of the antigenic relationships between strains of Bacteroides. intermedius, B. melaninogenicus, B. corporis, and B. denticola revealed by immunoblotting with rabbit antisera

Abstract

Antigen profiles of saccharolytic oral black-pigmented Bacteroides have been developed by Western blotting. Visual comparisons indicated extensive cross-reactions between B. intermedius, B. melaninogenicus, B. denticola, and B. corporis. Porphyromonas gingivalis, P. asaccharolyticus, and B. buccae showed less cross-reaction. Quantitation of antigenic similarity was made from densitometric scans. Calculation of the Jackard coefficient gave results of 33–72% similarity among the saccharolytic pigmented species, with the two homology groups of B. intermedius separated at 53%. Species were separated below 70%. Subtraction of the profile of a cross-reacting strain from that of the homologous strain also allowed quantitation of similarities. These similarities were lower; the range between species was 4–62%, although the two homology groups of B. intermedius still separated at 50 and 58%. Species were separated below 63%. Sera absorbed with a cross-reacting strain gave reduced reactions with the homologous strain and cross-reacting strains, indicating several common antigens among the four species. The species-specific antigens demonstrated by sera absorbed with cells of cross-reacting species were relatively few (3–6) compared with cross-reacting antigens detected by non-absorbed sera (18–28). The method appears useful to quantitate antigenic similarities among Bacteroides species and strains and allows analysis and quantitation of individual humoral responses in animals to these bacteria. Key words: oral Bacteroides, Porphyromonas, antigenic similarities, immunoblotting.