Oral Reduction of Nitrate Increases During Recovery From Antiseptic Mouthwash

Objectives: Nitric Oxide (NO) is an important signaling molecule in human health. NO is produced by bacterial reduction of the nitrates (NO₃) or nitrites (NO₂) that are in food. Many of these NO-producing bacteria are found on the tongue, and can be impacted use of antiseptic mouth rinses. In this study we assess bacterial viability and nitrate metabolism of the human tongue microbiome hourly for 8 hours after of Chlorhexidine use.
Methods: The subjects in the study are 10 dental health professionals. Tongue microbiome samples were obtained from the tongue dorsum using a stainless steel tongue scraper after rinsing with Chlorhexidine. A total of 10 samples were collected, at baseline, after CHX rinse, and hourly afterward for 8 hours. Samples were used to analyze viability of bacterial cells and plated on Aerobic TSBV media and Anaerobic TSBY-S media and incubated for 48-72 hours in aerobic or anaerobic conditions, respectively. Metabolic activity of nitrate reduction and nitrite production in tongue samples was measured with Griess Reagent. Significant changes in bacterial viable counts, nitrate and nitrite reduction activity were assessed using ANOVA, with significant differences between individual time points determined with post-hoc Fishers test.
Results: There was a 2.3 fold decrease in aerobic colony forming units beginning 1 hour after CHX exposure that began to recover at the 7^th hour. Anaerobic bacterial viability gradually decreased over the first 6 hours of the study; anaerobic counts were significantly lower than baseline at hours 5 and 6. Both aerobic and anaerobic counts began to recover at hours 7-8. Reduction of nitrate to nitrite was unchanged until the 8^th hour after CHX use, when a significant reduction in nitrate occurred simultaneously with a significant increase in nitrite.
Conclusions: Increased metabolic reduction of nitrate to nitrite is linked to bacterial recovery after exposure to CHX.