Suppressive Effects of Octyl Gallate on Streptococcus mutans Biofilm Formation, Acidogenicity, and Gene Expression.

Vika Gabe,Saleh Abu-Lafi,Basheer Abu-Farich,Anwar Rayan,Donatas Austys,Mouhammad Zeidan,Mahmud Masalha,Tomas Kacergius

doi:10.3390/molecules24173170

Abstract

The accumulation of biofilm by Streptococcus mutans bacteria on hard tooth tissues leads to dental caries, which remains one of the most prevalent oral diseases. Hence, the development of new antibiofilm agents is of critical importance. The current study reports the results from testing the effectiveness of octyl gallate (C8-OG) against: (1) S. mutans biofilm formation on solid surfaces (polystyrene, glass), (2) acidogenicity, (3) and the expression of biofilm-related genes. The amount of biofilm formed by S. mutans bacteria was evaluated using the colorimetric method and optical profilometry. The pH of the biofilm growth medium was measured with microelectrode. A quantitative reverse transcription-polymerase chain reaction (RT-qPCR) was used to assess the expression of genes encoding glucan binding protein B (gbpB), glucosyltransferases B, -C, -D (gtfB, -C, -D), and the F-ATPase β subunit of the F1 protein (atpD). The results show that C8-OG significantly diminished biofilm formation by exposed S. mutans on solid surfaces and suppressed acidogenicity in a dose-dependent manner, compared to unexposed bacteria (p < 0.05). The C8-OG concentration of 100.24 µM inhibited S. mutans biofilm development on solid surfaces by 100% and prevented a decrease in pH levels by 99%. In addition, the RT-qPCR data demonstrate that the biofilm-producing bacteria treated with C8-OG underwent a significant reduction in gene expression in the case of the four genes under study (gbpB, gtfC, gtfD, and atpD), and there was a slight decrease in expression of the gtfB gene. However, C8-OG treatments did not produce significant expression change compared to the control for the planktonic cells, although there was a significant increase for the atpD gene. Therefore, C8-OG might be a potent antibiofilm and/or anticaries agent for oral formulations that aim to reduce the prevalence of dental caries.

Highlights

Dental biofilm formation is primarily induced by Streptococcus mutans bacteria colonizing the human mouth [1]
The accumulation of biofilm produced by Streptococcus mutans bacteria on hard tooth tissues remains one of the most prevalent oral diseases, so that the development of new antibiofilm agents is of critical importance
Our results show that C8-OG significantly diminished biofilm formation by

Summary

Introduction

Dental biofilm formation is primarily induced by Streptococcus mutans bacteria colonizing the human mouth [1]. The development of biofilm on tooth surfaces results from the cooperative action of the S. mutans glucosyltransferases, GtfB, -C, and -D, which use dietary sucrose to synthesize water-insoluble, partly soluble, and soluble glucan polymers, respectively [2]. The subsequent bacterial fermentation of carbohydrates (e.g., sucrose) into organic acids causes the acidification of dental biofilm [1]. The constant acidogenicity of the biofilm induces tooth demineralization, leading to cavitation or dental caries, which continues to exhibit high global prevalence, despite the availability of various prophylactic measures [5,6]. There is a need for the development of new antibiofilm and/or anticaries agents

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Results

Conclusion