Genotypic diversity and virulence factors of Streptococcus mutans in caries-free and caries-active individuals

The objective of this study was to analyze the genotypic diversity, frequency of serotypes and the detection of mutacins from Streptococcus mutans isolates in caries-free and caries-active individuals.A total of 260 S. mutans isolated from 28 individuals with and without dental caries were subjected to AP-PCR and PCR screening of glucosyltransferase B, mutacin and serotype genes, which showed the presence of. 70 different genotypes. There was no statistically significant association between the presence of genes for serotypes and mutacins with dental caries. However, there was a statistically significant and a strong association between the higher genotypic diversity in the subjects with caries (r = 0.72, p = 0.001). There was an increase in the number of genotypes with increasing age (p <0.01).

Mutacins of Streptococcus mutans

The colonization and accumulation of Streptococcus mutans are influenced by various factors in the oral cavity, such as nutrition and hygiene conditions of the host, salivary components, cleaning power and salivary flow and characteristics related with microbial virulence factors. Among these virulence factors, the ability to synthesize glucan of adhesion, glucan-binding proteins, lactic acid and bacteriocins could modify the infection process and pathogenesis of this species in the dental biofilm. This review will describe the role of mutacins in transmission, colonization, and/or establishment of S. mutans, the major etiological agent of human dental caries. In addition, we will describe the method for detecting the production of these inhibitory substances in vitro (mutacin typing), classification and diversity of mutacins and the regulatory mechanisms related to its synthesis.

Cloning of mutA and expression of its coding protein / 实用口腔医学杂志

Objective:To obtain mutA gene of Strepto c occus mutans (Ms),and to express it in E.coli DH5?.Methods: mutA gene was amplified by PCR with specific primers from genome of Ms CH43 strain. After sequencing, the gene segment was inserted into vector pProEX and expressed in E.coli DH5?.The protein expression was induced by ITPG an d the protein products were examined by 180 ml/L SDSPAGE electrophorosis. Results:The length of PCR product was 147 bp and was identical to mu tA gene reported by GenBank.The mutA gene product was expressed in E.col i DH5? with Mr of 5.7?10 3.The maximum mutA protein product amount (20% of the total bacterial protein) was obtained when the A 600 value of DH5? was 1.666,IPTG concerntration 1.0 mmol/L and induction time 6 h.Conclus ion:mutA of Ms CH43 can be cloned and expressed in E.coli DH 5?.

Preparation and antibacteria activity of crude mutacin from clinical isolate of Mutans streptococci / 实用口腔医学杂志

Objective:To obtain crude mutacin produced by clinical isolate of Mutans streptococci (Ms) and to test its antibacteria activity. Methods:The mutacin in supernatant of in vitro cultured clinical isolate of Ms was extracted by chloroform, the antibacteria activity and heat stability of the crude extract were tested by bacteria culture technique. Results:Crude extract of protein was obtained fom clinical isolate of Ms. 10 ml of the liquid extract produced a 19 mm inhibitory zone in cultrue dish, indicating its antibacteria activity. The activity could maintain in 80 ℃ for 120 min, indicating its heat stability. Conclusion: The crude extract can represent the antibacteria activity and heat stability of mutacin.