Abstract
Early childhood caries (ECC), a severe form of caries due to cross-kingdom interaction of Candida albicans and Streptococcus mutans, is a serious childhood dental disease that affects majority of the children with poor background. The present study investigated the anti-infective potential of thymol against C. albicans and S. mutans dual species for the management of ECC. Thymol, a plant derivative of the monoterpene group, has been well known for its numerous biological activities. Thymol at 300 μg/ml concentration completely arrested growth and proliferation of dual species of C. albicans and S. mutans. Rapid killing efficacy of pathogens, within a span of 2 min, was observed in the time kill assay. In addition, at sub-inhibitory concentrations, thymol effectively diminished the biofilm formation and virulence of both C. albicans and S. mutans such as yeast-to-hyphal transition, hyphal-to-yeast transition, filamentation, and acidogenicity and acidurity, respectively, in single and dual species state. qPCR analysis was consistent with virulence assays. Also, through the invertebrate model system Galleria mellonella, in vivo toxicity and efficacy of the phytocompound was assessed, and it was found that no significant toxic effect was observed. Moreover, thymol was found to be proficient in diminishing the infection under single and dual state in in vivo condition. Overall, the results from the present study illustrate the anti-infective potential of thymol against the ECC-causing dual species, C. albicans and S. mutans, and the applicability of thymol in medicated dentifrice formulation.
Highlights
The oral microbiome of humans comprises more than 700 different species of microorganisms, including bacteria, fungi, mycoplasma, viruses, archaea, and protozoa (Marsh and Zaura, 2017)
One of the prime factors that contribute to the severe destruction of teeth in early childhood caries (ECC) is the extended consumption of sucrose-rich foods and beverages, which is due to the increased physical coadhesion between C. albicans and S. mutans as well as colonization on the tooth surface
It was evident that thymol exerts the growth inhibitory effect against single and dual species of C. albicans and S. mutans in a concentrationdependent manner (Figure 1B)
Summary
The oral microbiome of humans comprises more than 700 different species of microorganisms, including bacteria, fungi, mycoplasma, viruses, archaea, and protozoa (Marsh and Zaura, 2017). ECC has been reported to be the most common childhood oral disease that extremely affects the poor and minority children of age less than 6 years all over the world (Dye et al, 2012; Kassebaum et al, 2015) This severe form of caries is characterized with massive and painful destruction of teeth. The enzyme glycosyltransferases secreted by S. mutans bind with the cell surface of C. albicans and foster conversion of sucrose to extracellular polysaccharides (EPS), which further provides a binding site for S. mutans (Ikono et al, 2019) This unusual interaction further increases the localized microbial burden, acidurity, and production of the extracellular matrix. This mixed-kingdom interaction leads to sever tooth decay (Falsetta et al, 2014)
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