Prevalence of Filifactor alocis and Its RTX Protein-Encoding Gene, ftxA, Among Periodontitis Patients in Sweden

The oral pathogen Filifactor alocis encodes a repeats-in-toxin (RTX) protein, FtxA, that is encoded by the ftxA gene; it is present in approximately 50% of known isolated strains from various infected oral sites, including periodontitis, peri-implantitis, and root canal infections. It has been determined from PCR assessment of periodontally diseased cohorts in Ghana and Australia. Based on current knowledge, ftxA appears to be associated with both the progress and severity of periodontitis. This finding could potentially be linked to enhanced levels of ftxA-positive F. alocis, relative to ftxA-negative strain, and/or, in addition, a synergy between ftxA-positive strains and other periodontal pathogens. The exact mechanism remains unclear but may depend on an FtxA-mediated shifting of the host cell response toward immunosuppression. The main objective of the present work was to evaluate the prevalence and loads of F. alocis and the presence of ftxA in subgingival plaque in patients recruited for periodontal treatment in Sweden. This observational study included all samples that were received from external clinics over one full year (n = 71 patients). Our findings revealed that F. alocis was carried by 49 (69%) of the individuals, with the prevalence of ftxA amounting to 42.9% (n = 21). In 32 of the 71 samples, F. alocis could be quantitatively assessed. In this sub-population of F. alocis-positive patients, high loads of the bacterium were not related to age, and high loads were more frequently observed upon carriage of ftxA. The presence of, and co-colonization with, F. alocis with four additional periodontal pathogens was also evaluated. F. alocis was notable in that it co-colonized with all of the other species. Moreover, it was detected alongside two and even three of the other species within the same sample.