Influence of sugar and stevia to the cariogenicity of oral streptobacilli

Sai, Mei Ying (2023) Influence of sugar and stevia to the cariogenicity of oral streptobacilli. Final Year Project, UTAR.

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Abstract

Dental caries is one of the major health concerns caused by the acidogenic and cariogenic plaque bacteria which are frequently exposed to sugar. The colonization of rare oral streptobacilli could induce the occurrence of dental caries as they are biofilm-forming and acid producing oral bacteria. This project aims to study three aspects that involve in the cariogenicity which are the biofilm-forming strength, acidogenicity, and thickness of biofilm formation. Hence, three different growth conditions, including sugar free condition, BHI broth supplemented with 1% (w/v) sugar (sugar-dependent, SD), and BHI broth supplemented with 0.15% (v/v) stevia (stevia-dependent, StD) were implemented. A total of three target isolates were isolated from the dental plaque in which two were Gram-positive, catalase-positive and one was Gram-negative, catalase negative. In the MTP assay, biofilm-forming strength of the isolates were assessed quantitatively based on the intensity of solubilized 0.1% (w/v) crystal violet stained in the biofilm. One target isolate showed significant outcome (p<0.05) of moderate biofilm-forming strength in SD condition and weak biofilm-forming strength in StD condition whereas another two isolates were excluded as they were unable to grow in broth medium and lead to pooroutcome in the MTP assay, respectively. The Gram-positive target isolate was identified as Bacillus sp. using 16S rRNA sequencing Besides, the scanning electron microscopic examination showed significant increased (p<0.05) in the thickness of biofilm formation of the Bacillus sp. under SD and StD conditions. Furthermore, the acidogenicity of the target isolate was determined via the acid detection test. The target isolate demonstrated a significant decreased (p<0.05) of pH in SD condition as compared to the StD condition. Overall, the outcomes demonstrated that Bacillus sp. may cause cariogenic effects under the presence of sugar.

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