Abstract
Streptococcus mutans, with the ability of high-rate acid production and strong biofilm formation, is considered the predominant bacterial species in the pathogenesis of human dental caries. Natural products which may be bioactive against S. mutans have become a hot spot to researches to control dental caries. LongZhang Gargle, completely made from Chinese herbs, was investigated for its effects on acid production and biofilm formation by S. mutans in this study. The results showed an antimicrobial activity of LongZhang Gargle against S. mutans planktonic growth at the minimum inhibitory concentration (MIC) of 16% and minimum bactericidal concentration (MBC) of 32%. Acid production was significantly inhibited at sub-MIC concentrations. Biofilm formation was also significantly disrupted, and 8% was the minimum concentration that resulted in at least 50% inhibition of biofilm formation (MBIC50). A scanning electron microscopy (SEM) showed an effective disruption of LongZhang Gargle on S. mutans biofilm integrity. In addition, a confocal laser scanning microscopy (CLSM) suggested that the extracellular polysaccharides (EPS) synthesis could be inhibited by LongZhang Gargle at a relatively low concentration. These findings suggest that LongZhang Gargle may be a promising natural anticariogenic agent in that it suppresses planktonic growth, acid production, and biofilm formation against S. mutans.
Highlights
Dental caries is a chronic, progressive, and infectious disease which happens to the hard tissue of the teeth [1]
We determined the antimicrobial effect of LongZhang Gargle by measuring minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against S. mutans
The results showed that LongZhang Gargle inhibited the growth of planktonic S. mutans UA159 at a MIC of 16% and MBC of 32%
Summary
Dental caries is a chronic, progressive, and infectious disease which happens to the hard tissue of the teeth [1]. It is one of the most prevalent chronic human infectious diseases worldwide [2, 3]. Unlike most infectious diseases exhibiting classic virulence factors such as endotoxin (lipopolysaccharide, LPS), the etiologic factors of dental caries are initiated with the bacterial adherence to the tooth surface and dental plague biofilm formation. Cariogenic bacteria within dental plague biofilm produce acid by metabolizing carbohydrates ingested from the host, leading to demineralization of enamel surfaces and the development of caries [5, 6]. Reasons are as follows: S. mutans can adhere to enamel surfaces, it can synthesize extracellular polysaccharides (EPS) in the presence of carbohydrate, which mediates the irreversible adhesive interaction between bacterial cells and forms a highcell-density biofilm [10], and it exhibits a high-rate acid production and is highly aciduric, which allows it to survive and continue to produce acids in low pH microenvironments [11, 12]
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