Description of a polyvalent conjugate and a new serogroup of Bacteroides melaninogenicus by fluorescent antibody staining

Abstract

A polyvalent conjugate (fluorescein isothiocyanate-labeled antibody reagent) containing serogroups A, B and C conjugates was prepared. This polyvalent conjugate gave a positive fluorescent antibody (FA) stain with 49 strains of B. melaninogenicus representing serogroups A, B and C. When additional strains (92 strains) of the 3 subspecies of B. melaninogenicus were examined by the FA stain with A, B and C, and polyvalent conjugates, 9 strains of B. melaninogenicus ssp. intermedius failed to give a positive stain with any conjugate. FA conjugate was prepared with the [rabbit] antiserum to 1 of these strains (532-70A); all 9 strains stained positively with this conjugate. These 9 strains were biochemically characteristic of B. melaninogenicus ssp. intermedius; these strains were designated as a new serogroup, serogroup C-1. A new polyvalent conjugate containing serogroups A, B, C and C-1 was prepared. This polyvalent conjugate stained positively with 23 representative strains from serogroups A, B, C and C-1. The new conjugates failed to stain positively with other anaerobes or aerobes tested. The 4 individual conjugates, and the polyvalent conjugate, may be used for a more rapid identification of B. melaninogenicus than is possible by biochemical testing.