Geographic Influence on Subgingival Microbiota in Health and Periodontitis: A Multinational Shotgun Metagenomic Study.

Aims: To assess the differences in the taxonomical and functional profile of the subgingival microbiota isolated from healthy subjects (HS) and patients with periodontitis (PP) from four different countries.

Methods: In this study, 80 subgingival samples from HS and PP from four different countries (Belgium, Chile, Peru, and Spain) were analyzed using shotgun metagenomic sequencing.

Results: The results indicated significant variation in α-diversity between HS and PP, segregated by country, with PP from Peru clearly standing out from the rest. In terms of composition, β-diversity was explained more by the country of origin (6.8%) than by the diagnosis (4.1%). In addition, more than 75 different taxa, 63 of which were identified at the species level, showed significantly different relative abundances when comparing the country of origin, diagnosis, and both variables combined. Moreover, 85 metabolic pathways showed significantly different relative abundances between HS and PP, with species commonly associated with periodontitis, such as Porphyromonas gingivalis and Tannerella forsythia, strongly contributing to the reinforcement of periodontitis-associated pathways. On the other hand, differences in functional profiles based on the country of origin were almost nonexistent, suggesting that variability in taxonomic profiles does not have a direct impact on healthy or periodontitis-associated functional profiles.

Conclusion: These findings suggest that microbial analysis should take into account the geographic origin of samples in order to provide a more accurate description of the subgingival microbiota. Moreover, they lay the groundwork for larger and more comprehensive studies that might analyze this phenomenon in the future.