Genetic diversity in Streptococcus mutans demonstrated by multilocus sequence typing.

CARLETTO-KÖRBER FPM, GONZÁLEZ ITTIG RE, VERA NS, JIMÉNEZ MG & CORNEJO LS.

Foz do Iguazú

Congreso; 90th General Session & Exhibition of the International Association of Dental Research- International Association of Dental Research Latin American Regional Meeting.; 2012

Objectives: The main purpose of this study is to characterize the genetic diversity of strains of Streptococcus mutans from Córdoba Province (Argentina). Methods: We obtained 37 strains of S. mutans isolated from saliva of children of 6-8 years, attending four urban-marginal schools. After DNA extractions, we amplified and sequenced three housekeeping genes: lepC, gyrA and gltA. Sequences were aligned; the number of alleles, the average allelic and nucleotide diversity for each gene were obtained. These sequences were compared with those available in GenBank to explore if some alleles of Córdoba were shared with other countries. The joint analysis of the alleles of the three genes allowed to define sequence types (STs) and the genetic Kimura-2-parameter distance among STs was calculated. We performed pairwise FST comparisons among the four schools. Results: From the 37 strains of S. mutans, we detected: a) 15 alleles in lepC (10 were shared with Japan and 5 were private of Córdoba); b) 7 alleles in gyrA (4 shared with Japan and Thailand, 1 only with Thailand and 2 were private); c) 13 alleles in gltA (5 shared with Japan and Thailand, 1 with Thailand, 2 with Japan, and 5 were private). The allelic diversity of the three genes allowed the identification of 29 STs in Córdoba. The STs diversity was 0.97, the nucleotide diversity 0.004 and the average genetic distance was 0.4%. Five of the STs were shared among the four schools and the pairwise FST comparisons revealed no significant differences. Conclusion: We detected a high STs diversity, but with low genetic differentiation. Several strains detected in Córdoba would be worldwide distributed, but other present only in Córdoba may be due to particular epidemiological characteristics. The shared STs and low genetic distances, may impede the differentiation among the four schools.