Pathogenic factors of Filifactor alocis and Streptococcus gordonii identified in patients with inflammatory periodontal diseases

Relevance. One of the key research areas in periodontology is the investigation of the pathogenetic role of individual periodontal pathogens and their microbial associations. With the advent of sequencing technologies and metagenomic analysis, the list of periodontal pathogens continues to expand, and new key pathogens, such as Filifactor alocis, are being identified. Analyzing the virulence factors and interactions of F. alocis with other biofilm-forming bacteria, especially early colonizers such as Streptococcus gordonii, remains an important task.

Objective. The aim of this study was to characterize the pathogenic factors of Streptococcus gordonii and Filifactor alocis in the oral microbiomes of patients with inflammatory periodontal diseases.

Materials and methods. The study involved samples of gingival sulcus contents from healthy individuals (n = 25) and patients with gingivitis (n = 15), as well as samples of periodontal pocket contents from patients with mild (n = 30) and moderate (n = 39) chronic periodontitis (CP). Based on 16S rRNA gene sequencing, the microbial composition of each sample was determined. DNA extracted from the samples was also used as a template for polymerase chain reaction (PCR) to amplify the GspB gene (encoding a serine-rich repeat glycoprotein) and the hsa gene (encoding a sialic acid-binding adhesin) of Streptococcus gordonii, as well as the FtxA gene (encoding an RTX toxin protein) of Filifactor alocis, using primers selected by the authors. Statistical analysis was performed using Statistica 10 software. Cramér’s V coefficient was applied to assess associations between bacterial species occurrence within the oral microbiomes and patient group classification.

Results. 16S rRNA gene sequencing identified Filifactor alocis and Streptococcus gordonii in the microbiomes of patients; these microorganisms were not detected in the microbiomes of healthy individuals. PCR analysis showed that in patients with gingivitis, only the GspB gene was detected (in 6.7% of cases). In patients with mild and moderate chronic periodontitis, both S. gordonii genes (hsa and GspB) were detected in 20% and 28.2% of cases, respectively, and the F. alocis FtxA gene was found in 13.3% and 23.1% of cases, respectively. However, none of the groups exhibited all three genes simultaneously.

Conclusion. S. gordonii and F. alocis are part of the oral microbiota associated with inflammatory periodontal diseases. Identifying their pathogenic factors helps elucidate the mechanisms by which these microorganisms contribute to the onset and progression of periodontal pathology. This knowledge may facilitate the development of more accurate and sensitive early diagnostic tools and support the identification of new therapeutic targets.

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