Abstract
Dental caries is a highly prevalent disease worldwide. It is caused by the cariogenic biofilms composed of multiple dynamic bacteria on dental surface. Streptococcus mutans and Streptococcus sanguinis are resident members within the biofilms and an antagonistic relationship has been shown between these two species. S. mutans, as the major causative microorganism of dental caries, has been reported to be inhibited by free D-cysteine (D-Cys). However, whether D-Cys could affect S. sanguinis and the interspecies relationship between S. mutans and S. sanguinis remains unknown. The aim of the current study was to investigate the effect of D-Cys on the growth and cariogenicity of dual-species biofilms formed by S. mutans and S. sanguinis. We measured dual-species biofilms biomass, metabolic activity, lactate production. We also detected the biofilms structure, the ratio of live/dead bacteria, extracellular polysaccharide (EPS) synthesis and bacterial composition in the dual-species biofilms. We found that D-Cys could reduce the metabolic activity and lactic acid production of dual-species biofilms (p < 0.05). In addition, biofilms formation, the proportion of S. mutans in dual-species biofilms, and EPS synthesis were decreased with D-Cys treatment. The results suggested that D-Cys could inhibit the growth and cariogenic virulence of dual-species biofilms formed by S. mutans and S. sanguinis, indicating the potential of D-Cys in clinical application for caries prevention and treatment.
Highlights
Dental caries is one of the most major and prevalent diseases worldwide[1]
Growth of the S. mutans and S. sanguinis affected by D-cysteine
We investigated the effect of D-Cys on the growth and cariogenicity of dual-species biofilms formed by S. mutans and S. sanguinis
Summary
Dental caries is one of the most major and prevalent diseases worldwide[1]. According to the statistics of the United States from 2011 to 2012, approximately 90% of U.S adults aged 20–64 had dental caries in permanent teeth[2]. While Streptococcus sanguinis is another indigenous species in the dental plaque. D-amino acids (D-AAs), as the component of cell wall peptidoglycan[10,11], were demonstrated to participate in regulating and disassembling bacterial biofilms. For this reason, D-AAs has been assumed to provide a new strategy for the prevention of biofilm-related diseases[12,13]. The present study was aimed to investigate the effect of D-Cys on dual-species biofilms formed by S. mutans and S. sanguinis. We hypothesized that: (1) D-Cys was able to inhibit the growth and metabiotic activity of the dual-species biofilms; (2) D-Cys could regulate the proportion of S. mutans and S. sanguinis and convert the biofilm to a healthier condition
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