Effect of a novel synbiotic on Streptococcus mutans

Mohammed Nadeem Bijle,Cynthia Kar Yung Yiu,Manikandan Ekambaram,Edward C M Lo,Prasanna Neelakantan

doi:10.1038/s41598-020-64956-8

Mohammed Nadeem Bijle, Cynthia Kar Yung Yiu + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-64956-8

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Journal: Scientific Reports	Publication Date: May 14, 2020
Citations: 26	License type: open-access

Affiliation: University of Hong Kong, University of Otago

Abstract

We examined the effect of L-arginine - (i) on the growth of L. rhamnosus GG (LrG) and (ii) combined LrG synbiotic on the growth of cariogenic S. mutans. Viability of LrG was assessed using MTT/XTT assays, confocal imaging with ADS activity measurement. The effect of L-arginine (0.5%/1%/2%) (2×/24 h) with LrG on S. mutans was evaluated by measuring the colony forming units, biofilm biomass, real-time qPCR and confocal imaging. The pH of the spent media was measured immediately and 24 h post-treatment with assessment of lactic acid. The LrG viability was highest with 2% L-arginine (p < 0.001). Confocal imaging showed that 2% L-arginine increased biofilm thickness of LrG. The 2% L-arginine and LrG synbiotic significantly inhibited the growth of S. mutans (p < 0.001) reducing the viable counts (p = 0.002) and biofilm biomass (p < 0.001). The pH of spent media was the highest when treated with 2% L-arginine and LrG synbiotic (p < 0.001) with no difference between post-treatment and 24 h post-treatment (p > 0.05). Conversely, the 2% L-arginine and LrG synbiotic showed the lowest lactic acid production (p < 0.001). This study demonstrated that L-arginine enhanced the growth of LrG. The 2% L-arginine and LrG synbiotic synergistically inhibits the growth of S. mutans with significant potential to develop as an anti-caries regimen.

Highlights

Dental caries, a dysbiosis-regulated biofilm-mediated disease, is an important public health problem worldwide[1]
The cell viability of the L. rhamnosus GG with 2% L-arginine group was significantly higher than 0.5% L-arginine and the control groups (p < 0.05)
Distinguishable dead/damaged bacterial cells of L. rhamnosus GG could be seen in biofilms treated with 0.5% L-arginine, which were not evident in the other groups (Fig. 1b)

Summary

Introduction

A dysbiosis-regulated biofilm-mediated disease, is an important public health problem worldwide[1]. Developed strategies to combat caries focus on ecological approaches, interfering with the physical and metabolic activities of the biofilm with an objective of preventing dysbiosis Such interventions use either antimicrobial strategies or approaches to enhance the growth of health-promoting bacteria[3]. Arginine has been used as an oral prebiotic to enhance the growth of alkalogenic health-promoting bacteria - Streptococcus sanguinis, Streptococcus parasanguinis and Streptococcus gordonii, with subsequent inhibition of the cariogenic bacterium - Streptococcus mutans[5] It enhances the antimicrobial and remineralization effects of fluoride[6,7]. The capital alphabets – A/B/C show significant difference among the groups with XTT assay and the small alphabets – a/b show significant differences among the groups with MTT assay); and (b) Representative confocal microscopic images (100×) of biofilms treated with 0.5%, 1%, 2% L-arginine and 0.9% NaCl

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