Periodontal treatment causes a longitudinal increase in nitrite-producing bacteria

Abstract

Background: The oral microbiome-dependent nitrate (NO₃ ^-)-nitrite (NO₂ ^-)-nitric oxide (NO) pathway may help regulate blood pressure. NO₂ ^--producing bacteria in subgingival plaque are reduced in relative abundance in patients with untreated periodontitis compared with periodontally healthy patients. In periodontitis patients, the NO₂ ^--producing bacteria increase several months after periodontal treatment. The early effects of periodontal treatment on NO₂ ^--producing bacteria and the NO₃ ^--NO₂ ^--NO pathway remain unknown. The aim of this study was to determine how periodontal treatment affects the oral NO₂ ^--producing microbiome and salivary NO₃ ^- and NO₂ ^- levels over time.

Methods: The subgingival microbiota of 38 periodontitis patients was analysed before (baseline [BL]) and 1, 7 and 90 days after periodontal treatment. Changes in NO₂ ^--producing bacteria and periodontitis-associated bacteria were determined by 16s rRNA Illumina sequencing. Saliva samples were collected at all-time points to determine NO₃ ^- and NO₂ ^- levels using gas-phase chemiluminescence.

Results: A significant increase was observed in the relative abundance of NO₂ ^--producing species between BL and all subsequent timepoints (all p < 0.001). Periodontitis-associated species decreased at all timepoints, relative to BL (all p < 0.02). NO₂ ^--producing species negatively correlated with periodontitis-associated species at all timepoints, with this relationship strongest 90 days post-treatment (ρ = -0.792, p < 0.001). Despite these findings, no significant changes were found in salivary NO₃ ^- and NO₂ ^- over time (all p > 0.05).

Conclusions: Periodontal treatment induced an immediate increase in the relative abundance of health-associated NO₂ ^--producing bacteria. This increase persisted throughout periodontal healing. Future studies should test the effect of periodontal treatment combined with NO₃ ^- intake on periodontal and cardiovascular health.

Keywords: 16s rRNA sequencing; nitrate; nitrite; oral nitrate reduction; periodontitis.