Identification of Bacteroides gingivalis by fluorescent antibody staining

Reactivity with the conjugates to the 4 serogroups A, B, C and C-1 of the former taxon Bacteroides melaninogenicus and with antisera to B. gingivalis and to oral strains of B. melaninogenicus subsp. intermedius, was studied by fluorescent antibody staining (FAS) on strains representative of the black-pigmented Bacteroides: B. asaccharolyticus, B. melaningogenicus subsp. intermedius, B. melaninogenicus subsp. melaninogenicus, B. melaninogenicus subsp. levii, B. melaninogenicus subsp. macacae and B. gingivalis. The strains of B. gingivalis only reacted with the homologous antiserum and failed to react with any of the other immunoreagents tested indicating that the oral strains of asaccharolytic black- pigmented Bacteroides belong to a serogroup distinct from those currently serogrouped. This serological characteristic corroborates the definition of the new species B. gingivalis which has been proposed on the basis of phenotypic and genetic characteristics different from that of B. asaccharolyticus and can be used for their discrimination. FAS appears to be a reliable method for identification of B. gingivalis, a suspected major periodontopathic organism.