Anti-Streptococcus mutans property of Uvaria chamae, and its anticariogenecity
Introduction Dental caries is the most prevalent oral infection. Streptococcus mutans is a major cause of dental caries in humans. These bacteria form biofilms and produce acids and extracellular polysaccharides which contribute to the development of dental caries. Many oral hygiene products containing antimicrobial chemicals have been used to prevent dental caries. In recent years, medicinal plants have been researched for their beneficial properties in the prevention of dental caries. Uvaria chamae have been used to treat various infections. It has proven antiparasitic, antiplasmodial, antidiabetic, antimicrobial, and antioxidant properties. Although the anti-S. mutans activity of this plant has been reported, its effect on the virulence properties has not been studied. Therefore, this study aimed to investigate the antimicrobial activity of U. chamae roots extracts on S. mutans virulence factors. Methods and materials Stock cultures of S. mutans were obtained from the Oral microbiology laboratory, the University of the Witwatersrand, and the plant extracts were provided by Dr. Ogunyemi Olajide Oderinlo from Nigeria. The plant extracts were prepared using methanol, dichloromethane, hexane, ethanol, and methanol: water. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined using the microdilution technique. Based on the MIC, the solvent with the best results was selected and three different concentrations were evaluated for their effect on biofilm formation, acid, and extracellular polysaccharides production in S. mutans. The effect of the plant extract on the expression of virulence genes (gtfB, gtfC, spaP, IDH, atpD, vicR, brpA, and gbpB) was also investigated using RT-qPCR. The results were analyzed using the one-way ANOVA and Wilcoxon Rank Sum Test. Results The mean MIC of U. chamae roots extracts against S. mutans ranged between 0.02 and 1.25 mg/ml and the MBC ranged between 0.04 and 1.25 mg/ml. The dichloromethane plant extract showed the best antibacterial activity against all the five cariogenic S. mutans strains with an average MIC and MBC of 0.02 and 0.04 mg/ml respectively and was used in the subsequent experiments such as the biofilm, acid, EPS, and RT-qPCR assay. At 6 hours, exposure to 0.005, 0.01, and 0.02 mg/ml of the plant extract reduced biofilm formation by 39.70, 59.17, and 76.82 % respectively. At 24 hours, the percentage reduction of the biofilm counts significantly improved up to 91 %. Not much difference in the test results was observed between 24 and 30 hours. The plant extract also significantly inhibited acid production (p < 0.01). The roots extract did not inhibit the production of soluble and insoluble extracellular polysaccharides. Furthermore, a significant decline in the transcription of virulence genes (gbpB, vicR, brpA, spaP, gtfB, gtfC, atpD, and IDH) was observed in the presence of the plant extract. Conclusion The dichloromethane extracts showed the best antibacterial activity. At subinhibitory concentrations, this plant extract significantly inhibited biofilm formation, acid production, and virulent gene expression by S. mutans. Therefore, this suggests that U. chamae has the potential to control and prevent dental caries.
A dissertation submitted in fulfillment of the requirements for the degree of Master of Science in Medicine to the Faculty of Health Sciences, School of Pathology, University of the Witwatersrand, Johannesburg, 2022