Genotypic and phenotypic characterization of Streptococcus mutans isolated from dental caries

Abstract

25Streptococcus mutans, considered as principal causative agent of dental caries, maintains 26 a biofilm lifestyle in the dental plaque. The oral cavity harbors numerous S. mutans strains, which 27 displayed remarkable genotypic and phenotypic diversity. This study evaluated the genotypic and 28 phenotypic diversity of 209 S. mutans strains isolated from 336 patients with dental caries and 29 compared with the universal reference strain UA159. Our study has revealed a high degree of 30 genotypic and phenotypic variability among the clinical strains. We observed significant 31 differences in colony morphology, generation time, biofilm formation, bacteriocin and acid 32 production while growing in culture medium. All the clinical isolates were able to lower pH while 33 growing in THY broth. In consistent with phenotypic variations, we also observed tremendous 34 level of genotypic variation by AP-PCR and gene specific PCR. AP-PCR analysis suggested that 35 most of the patients with dental caries have distinct type of S. mutans strains. Genes related to 36 various two component systems were highly conserved among the strains, however, bacteriocin 37 encoding genes such as nlmAB, nlmC were absent in half of the clinical isolates. In sum, our study 38 highlights the genotypic and phenotypic diversity of S. mutans clinical isolates and indicates the 39 presence of diverse mechanism to initiate and establish the biofilm lifestyle which leads to tooth 40 decay. 41 42 43 44 45 46 48The initiation and successful development of dental caries is caused by multiple bacterial 49 and host factors, such as the composition and biochemical activity of the biofilm organisms, 50 dietary habit, genetic constitution and behavior of the host, tooth architecture and exposure to 51 fluoride (1-4). The mutans streptococci, specifically S. mutans, are considered to be the primary 52 causative agents of dental caries, commonly known as tooth decay (5, 6). In addition, several recent 53 studies have reported the associations of certain sub-groups of S. mutans with cardiovascular 54 disease (7-11). The ability to form biofilm on tooth surface, production of organic acid from 55 various carbohydrates (acidogenicity), ability to survive at low pH (acidurance), outstanding 56 ability to outcompete other bacteria by the production of bacteriocin and their adaptability to 57 rapidly changing environment can be attributed as the major virulence factors (12-18). 58Development of natural competence, which is coordinately regulated with the bacteriocin 59 production, is another vital attribute that provides genetic diversity to S. mutans for niche 60 adaptation and colonization (19-21). 61Strains belong to the species, S. mutans, are generally classified into four (c, e, f, and k) 62 serological groups based on the composition of cell-surface rhamose-glucose polysaccharides (22, 63 23). Strains belonged to serotype c are the most abundant in the oral cavity (70-80%), followed 64 by serotype e (20%) and serotype f or k (2-5%) (1, 24). However, serot...

Formulation and evaluation of dental gels and pastilles containing xylitol for dental caries

“…Dental caries or cavities represent damage to the hard tissues of the tooth caused by organic acids produced from carbohydrate fermentation by endogenous Streptococcus mutans in the oral cavity (Hossain et al, 2021;Peres et al, 2019). Because of the negative effects on human well-being, dental caries is a significant oral health problem in people of all ages.…”