Genotypic and phenotypic characterization of Streptococcus mutans strains isolated from patients with dental caries

Mohammad Shahadat Hossain; Sadab Alam; Yead Morshed Nibir; Tahrima Arman Tusty; Sayyeed Mahmud Bulbul; Mirajul Islam; Mohammad Shahnoor Hossain

doi:10.18502/ijm.v13i4.6968

Mohammad Shahadat Hossain Department of Genetic Engineering & Biotechnology, University of Dhaka, Dhaka, Bangladesh
Sadab Alam Department of Genetic Engineering & Biotechnology, University of Dhaka, Dhaka, Bangladesh
Yead Morshed Nibir Department of Genetic Engineering & Biotechnology, University of Dhaka, Dhaka, Bangladesh
Tahrima Arman Tusty Department of Genetic Engineering & Biotechnology, University of Dhaka, Dhaka, Bangladesh
Sayyeed Mahmud Bulbul Department of Genetic Engineering & Biotechnology, University of Dhaka, Dhaka, Bangladesh
Mirajul Islam Department of Statistics, Faculty of Sciences, University of Dhaka, Dhaka, Banglades
Mohammad Shahnoor Hossain Department of Genetic Engineering & Biotechnology, University of Dhaka, Dhaka, Bangladesh

DOI: https://doi.org/10.18502/ijm.v13i4.6968

Keywords: Dental caries; Streptococcus mutans; Genotype; Phenotype; Virulence

Abstract

Background and Objectives: The oral cavity harbors numerous Streptococcus mutans strains which display remarkable genotypic and phenotypic diversity. This study evaluated the genotypic and phenotypic diversity of 209 S. mutans strains isolated from 336 patients with dental caries and compared with the universal reference strain, UA159.

Materials and Methods: Selective cultivation on mitis-salivaries-bacitracin agar and species-specific polymerase chain re- action (PCR) was carried out to isolate and identify the 209 S. mutans isolates from 336 patients with dental caries. Arbitrari- ly primed polymerase chain reaction (AP-PCR), PCR amplification of specific gene, acid production and biofilm formation capacity were performed to evaluate the genotypic and phenotypic variation. Student’s t-test and Chi-square test were used for analysis of variables and a probability (P) of <0.05 was considered as significant.

Results: Our study revealed a high degree of genotypic and phenotypic variability among the clinical strains. We observed significant differences in colony morphology, generation time, biofilm formation, and acid production while growing in cul- ture medium. All the clinical isolates were able to lower pH while growing in Todd-Hewitt broth. Consistent with phenotypic variations, we also observed genotypic variation by AP-PCR and gene specific PCR. AP-PCR analysis suggested that most of the patients with dental caries have distinct type of S. mutans strains. Genes related to various two component systems were highly conserved among the isolated strains, however, bacteriocin encoding genes such as nlmAB, nlmC were absent in nearly half of the clinical isolates.

Conclusion: Our results support that S. mutans clinical isolates have wide genotypic diversity and show variation in growth kinetics, acid production, acid tolerance and biofilm formation capacity and indicates the presence of diverse mechanism to initiate and establish the biofilm lifestyle which leads to tooth decay.