Sorotipos e genes de proteínas de ligação ao colágeno de streptococcus mutans na cárie na primeira infância

Abstract

The presence of multiple serotypes and genes encoding collagen-binding proteins (cnm and cbm) of Streptococcus mutans has been associated with increased risk and severity of dental caries. The present study aimed to investigate, using the polymerase chain reaction technique, the occurrence of serotypes (c, e, f and k) and collagen binding genes, cnm and cbm, of S. mutans in biofilm of caries-free children, and in biofilm and dentin caries lesions of children with Early Childhood Caries (ECC). The population consisted of 80 Brazilian children aged 2 to 6 years who had samples previously collected and DNA extracted and frozen. The samples (n=107) were divided according to the following groups: biofilm from caries-free children (BLC) (n=19); biofilm from children with enamel caries lesions (BLE) (n=16); biofilm from children with carious dentin lesions (BLD) (n=34) and carious dentin (DC) collected from active (DCA) (n=28); and inactive dentin caries (DCI) (n=10) lesions of children with ECC. Data were tabulated in Microsoft Excel and statistical analysis was performed using the Statistical Package for Social Sciences (SPSS) statistical software. Chi-square and Fisher's exact tests were used to analyze S. mutans serotypes and genes. Mann-Whitney or Kruskal-Wallis tests were applied for comparison between groups. Regarding the prevalence of S. mutans serotypes in positive samples for this microorganism (n=78), it was observed that serotype c was the most frequent (72.89%), followed by f (28.2%), k (25.64%) and e (7.69%). In biofilm samples, it was found that there was 23.61 times greater chance of detecting serotype c in the BLD group when compared to the BLC group (95%CI: 4.53 - 123.12; p<0.001). Furthermore, it was observed that the detection of serotypes c, f, or k is related to biofilm samples from children with greater caries severity. The presence of more than one serotype in biofilm samples is associated with a greater experience of caries in children when compared with the detection of a single serotype (p=0.012) or no serotype (p<0.001). Comparing the BLD and DC groups, it was found that dentin is 6.75 times more likely to detect serotype f when compared to biofilm (95%CI: 1.99 -22.92; p=0.002), as well as serotype k (95%CI: 1.43 - 16.73; p=0.011). Regarding the detection of the cnm/cbm genes, it was observed that there was 12.77 times more chance of identifying the cbm gene in carious dentin when compared to the BLD group (95%CI: 3.32 - 49.07; p<0.001). In this study, a greater caries experience in children with ECC was associated with multiple serotypes of S. mutans. The detection of serotypes f and k in addition to the cbm gene in dentin caries lesions is related to greater caries severity. The findings of this study suggest that serotypes of S. mutans and the cbm gene may play a particularly relevant role in dentin caries lesions in children with ECC.