Abstract
Streptococcus mutans has been considered as the major etiological agent of dental caries, mostly due to its arsenal of virulence factors, including strong biofilm formation, exopolysaccharides production, and high acid production. Here, we present the antivirulence activity of fatty acids derived from the endophytic fungus Arthrographis kalrae isolated from Coriandrum sativum against Streptococcus mutans. The chemical composition of the fatty acids was analyzed by gas chromatography–mass spectrometry GC-MS and revealed nine compounds representing 99.6% of fatty acids, where unsaturated and saturated fatty acids formed 93.8% and 5.8 % respectively. Oleic and linoleic acids were the major unsaturated fatty acids. Noteworthy, the fatty acids at the concentration of 31.3 mg L–1 completely inhibited Streptococcus mutans biofilm, and water insoluble extracellular polysaccharide production in both polystyrene plates, and tooth model assay using saliva-coated hydroxyapatite discs. Inhibition of biofilm correlated significantly and positively with the inhibition of water insoluble extracellular polysaccharide (R = 1, p < 0.0001). Furthermore, Arthrographis kalrae fatty acids at a concentration of 7.8 mg L–1 exhibited acidogenesis-mitigation activity. They did not show bactericidal activity against Streptococcus mutans and cytotoxic activity against human oral fibroblast cells at the concentration used. On the other hand, saliva-coated hydroxyapatite discs treated with sub-minimum biofilm inhibitory concentration of fatty acids showed disturbed biofilm architecture with a few unequally distributed clumped matrices using fluorescence microscopy. Our findings revealed that the intracellular fatty acid arrays derived from endophytic Arthrographis kalrae could contribute to the biofilm-preventing alternatives, specifically Streptococcus mutans biofilms.
Highlights
Dental caries is a predominant worldwide oral disease affecting almost half of the world’s population [1]
Among the numerous bacteria associated with dental caries pathogenesis, the main cariogenic microbe is Streptococcus mutans (S. mutans) that inseparably relies on a set of virulence factors to establish cariogenic infection by formation of a strong biofilm
The results demonstrated that discs treated with MBIC50 of Arthrographis kalrae Fatty Acids (AKFAs) showed few clumped matrices that were unequally distributed with lower surface adherence (Figure 7D)
Summary
Dental caries is a predominant worldwide oral disease affecting almost half of the world’s population [1]. The formation of oral biofilm starts by the adsorption of saliva on the tooth enamel resulting in the formation of a complex mixture of glycoproteins, acidic proline–rich proteins, mucins, bacterial cell debris, exoproducts, and sialic acid. Among the numerous bacteria associated with dental caries pathogenesis, the main cariogenic microbe is Streptococcus mutans (S. mutans) that inseparably relies on a set of virulence factors to establish cariogenic infection by formation of a strong biofilm These factors include initial adherence to the tooth through high-affinity adhesins, accumulation and persistence of bacteria due to EPS production, high rate acid production attributable to its higher ability to metabolize sucrose in addition to its acid resistance and ability to grow at low pH [5,7,8,9]. Based on the particular attention drawn on the biological activities of endophytic metabolites—specially, antimicrobial lipids in numerous studies [23,24,25,26]—the present study aimed at extracting fatty acids from an endophytic fungus isolated from Corandium sativium leaves and investigate the antivirulence activity of the extracted fatty acids combination against S. mutans
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