Polymerase chain reaction amplification of the constant and variable regions of the Bacteroides nodosus fimbrial gene.

Serogrouping of Bacteroides nodosus is based on antigenic differences in fimbriae of the different New Zealand prototype strains. Because of the time needed to isolate and grow pure cultures of B. nodosus and the difficulty in distinguishing between different serogroups because of cross-agglutination, a new DNA-based diagnostic approach based on the fimbrial gene sequence of B. nodosus was developed. Published nucleotide sequences of the fimbrial genes for serogroups A, G, D, and H showed conservation at the 5' end, coding for the N terminus, and variability at the 3' end, coding for the C terminus. The polymerase chain reaction was used to amplify both the constant and variable regions of the fimbrial genes. Constant-region oligonucleotide primers were used to amplify a 100-base-pair fragment from the constant regions of the fimbrial genes of 10 New Zealand serogroups. Serogroup-specific oligonucleotide primers for serogroups A and H allowed amplification of a 282-base-pair fragment from serogroup A and a 363-base-pair fragment from serogroup H. Thus, amplification of the constant and variable regions of the fimbrial gene allows rapid detection and grouping of B. nodosus.