Association of Filifactor alocis and its RTX toxin gene ftxA with periodontal attachment loss, and in synergy with Aggregatibacter actinomycetemcomitans

Abstract

The Gram-positive bacterium, <i>Filifactor alocis</i> is an oral pathogen, and approximately 50% of known strains encode a recently identified repeat-in-toxin (RTX) protein, FtxA. By assessing a longitudinal Ghanaian study population of adolescents (10-19 years of age; mean age 13.2 years), we recently discovered a possible correlation between deep periodontal pockets measured at the two-year follow-up, presence of the <i>ftxA</i> gene, and a high quantity of <i>F. alocis</i>. To further understand the contribution of <i>F. alocis</i> and FtxA in periodontal disease, we used qPCR in the present study to assess the carriage loads of <i>F. alocis</i> and the prevalence of its <i>ftxA</i> gene in subgingival plaque specimens, sampled at baseline from the Ghanaian cohort (n=500). Comparing these results with the recorded clinical attachment loss (CAL) longitudinal progression data from the two-year follow up, we concluded that carriers of <i>ftxA</i>-positive <i>F. alocis</i> typically exhibited higher loads of the bacterium. Moreover, high carriage loads of <i>F. alocis</i> and concomitant presence of the <i>ftxA</i> gene were two factors that were both associated with an enhanced prevalence of CAL progression. Interestingly, CAL progression appeared to be further promoted upon the simultaneous presence of <i>F. alocis</i> and the non-JP2 genotype of <i>Aggregatibacter actinomycetemcomitans</i>. Taken together, our present findings are consistent with the notion that <i>F. alocis</i> and its <i>ftxA</i> gene promotes CAL during periodontal disease.