# Rapid Griess assay (RGA): a chairside test for ex vivo semi-quantitative oral nitrite measurement and in vitro assessment of nitrite production by oral bacteria

## TL;DR

A new chairside test called the rapid Griess assay (RGA) was developed to measure nitrite levels in the mouth, revealing that certain bacteria produce significant amounts of nitrite.

## Contribution

The RGA is a novel semi-quantitative chairside test for measuring oral nitrite and assessing bacterial nitrite production.

## Key findings

- Tongue samples showed the highest and most stable nitrite levels over time.
- Actinomyces spp., Veillonella parvula, and Rothia spp. were identified as high nitrite-producing bacteria.
- The RGA provided reproducible and reliable results suitable for clinical and research use.

## Abstract

Nitrite (NO2−) is produced through enzymatic reduction of dietary nitrate (NO3−) by oral bacteria: a process contributing to cardiovascular – and possibly oral – health. NO2− quantitation in biological samples is a complex exercise, and available methods are not well-adapted for chairside use. Therefore, we aimed to develop and evaluate a semi-quantitative chairside test for NO2− in oral samples. We also evaluated NO2− generation in several bacterial species in vitro.

From 12 healthy individuals, tongue, saliva and plaque samples were collected and evaluated chairside across 4 weeks, using the rapid Griess assay (RGA). The RGA was further used to test bacterial species for NO2− production.

In saliva, plaque and tongue samples, low, variable and high NO2− levels, respectively, were found. Tongue samples were the most stable over time. High and medium NO2− production capacities were shown by Actinomyces spp. (including Schaalia odontolytica), Veillonella parvula, and Rothia spp. RGA results were reproducible.

The RGA provided stable and reliable results for chairside NO2− semi-quantitation, and revealed elevated and stable NO2− levels on the tongue. In vitro, bacterial NO2− production was consistent with the available literature, but uncertainty remains regarding Neisseria spp. Our results showed promise for clinical and research applications of the RGA.

The rapid Griess assay (RGA) showed promise as a chairside research tool for the exploration of oral NO2− production.Oral NO2− concentrations were highest on the tongue dorsum, and healthy individuals differed extensively in their oral NO2− production abilities.The oral bacterial species Actinomyces spp. (including Schaalia odontolytica), Rothia spp. Veillonella parvula and Aggregatibacter actinomycetemcomitans showed NO2− production with RGA method.

The rapid Griess assay (RGA) showed promise as a chairside research tool for the exploration of oral NO2− production.

Oral NO2− concentrations were highest on the tongue dorsum, and healthy individuals differed extensively in their oral NO2− production abilities.

The oral bacterial species Actinomyces spp. (including Schaalia odontolytica), Rothia spp. Veillonella parvula and Aggregatibacter actinomycetemcomitans showed NO2− production with RGA method.