Polymerase chain reaction for the detection of flaA-1 genes of oral spirochaetes in human advanced periodontal pockets

A novel group of oral spirochaetes that were specifically labeled by H9-2, a monoclonal antibody against the 37-kDa endoflagellar sheath protein of Treponema pallidum, have earlier been demonstrated in periodontitis-associated plaque samples; two cultivable oral spirochaetes T. vincentii and T. medium displayed cross-reactivity with that monoclonal, but the molecular basis for this cross-reactivity is not yet defined. Here, the flaA-1 genes which encode the 37-kDa sheath protein from T. vincentii and the oral spirochaetes present in samples from advanced periodontitis were examined. A 856 bp fragment of the flaA-1 gene was amplified in T. pallidum and T. vincentii. The same-size polymerase chain reaction fragments were also amplified in two clinical samples from patients with advanced periodontitis but not from samples of healthy plaque. The sequences of the flaA-1 genes of the oral spirochaetes detected in human periodontal plaque were closely similar to those of T. pallidum and T. vincentii, but neither of these two organisms could be detected in these samples using rRNA-specific primers. The identity of the flaA-1 positive spirochaetes associated with periodontitis remains to be determined.