Immunological specificity of oral Eubacterium species

Antigens of Eubacterium species including E. alactolyticum, E. brachy, E. nodatum, E. saburreum, E. timidum, E. yurii subsp. yurii and E. yurii subsp. margaretiae, which have been isolated frequently from periodontal pockets and associated with periodontal diseases, were extracted by ultrasonication from whole bacterial cells. Antigens were also prepared from E. aerofaciens, E. lentum and E. rectale, which have been found in intestinal tracts and infected abscesses in human oral cavities. The antigens of the oral Eubacterium species were compared with antigens from E. limosum, the type species of the genus Eubacterium, by using SDS-PAGE and Western immunoblot assays. SDS-PAGE gels stained with Coomassie brilliant blue indicated that no major peptide bands were common among the Eubacterium species examined. The protein profile patterns were distinctly different from each other. Western immunoblotting reactions with rabbit antisera showed that the Eubacterium species could be clearly distinguished serologically, and that the species-specific antigens were peptide components of ultrasonic extracts from the whole bacterial cells. The present study demonstrates that these Eubacterium species show great heterogeneity in their peptide components and immunological reactions, which may be useful for identification of the Eubacterium species from human oral specimens.