Protein banding patterns of the outer membrane-enriched fraction of Bacteroides bivius

Bacteroides bivius is a common anaerobe in female genital infections. Although protein banding patterns of outer membrane (OM) preparations of Bacteroides fragilis are well described and are homologous within the species, similar work has not been done with B. bivius. Our aims were to (i) characterize the OM banding patterns of B. bivius and compare them with those of other Bacteroides species and (ii) test clinical isolates of B. bivius against anti-B. bivius and anti-B. fragilis sera to identify different serogroups that might also exhibit different OM banding patterns. OM-enriched fractions of 27 clinical strains of B. bivius, 6 Bacteroides disiens strains, 10 B. fragilis strains, and 12 other Bacteroides strains were prepared, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis was performed. Antisera to B. bivius ATCC 29303 and B. fragilis ATCC 25285 were raised in rabbits and tested against Bacteroides strains in an indirect enzyme-linked immunosorbent assay. All 27 B. bivius strains contained protein bands at 32, 27, 25, and 23 kilodaltons. This pattern was present in only 2 of 28 other strains; both of these were B. disiens. All B. bivius strains were reactive with the anti-B. bivius serum, while only 6 of 39 other strains (2 of 6 B. disiens) were reactive. Non-B. fragilis Bacteroides strains did not react with the anti-B. fragilis serum. Although there was marked homogeneity in the OM banding patterns of B. bivius, some B. disiens strains exhibited similar OM banding patterns. There appears to be some antigenic cross-reactivity between strains of B. bivius and B. disiens and very little with other Bacteroides species. These results may ultimately allow the development of rapid diagnostic tests for the B. bivius-B. disiens group.t