Evaluación de Streptococcus dentisani y Streptococcus mutans en biopelícula dental de niños con y sin caries

Abstract

Background: dental caries is a multifactorial condition that affects adults and children worldwide. It is characterized by the destruction of dental hard tissues as consequence of demineralization caused by organic acids produced by acidogenic bacteria present in the biofilm. Streptococcus mutans (S. mutans) is considered one of the most important etiological agents associated with dental caries due to its ability to metabolize carbohydrates and the capacity to live in acid environments. On the other hand, Streptococcus dentisani (S. dentisani), a new species that has been isolated from the dental biofilm, shows characteristics associated with caries control due to its ability to inhibit growth of cariogenic bacteria by producing bacteriocins, thus increasing the pH of the oral cavity by metabolizing arginine. The objective of this investigation was to evaluate the presence of S. dentisani and S. mutans in the biofilm of children with and without dental caries and determine the proportion of such species according to the presence or absence of caries. Materials and methods: Visual calibration and identification of species was performed by macroscopic characterization of colonies using reference strains (S. dentisani, CECT 7746 and S. mutans, ATCC 25175). Samples of dental biofilm from 10 children with and without dental caries were collected and were inoculated into selective growth media. 35 isolates clinically and morphologically compatible with S. dentisani colonies and 35 isolates clinically and morphologically compatible with S. mutans colonies were selected for molecular identification by Polymerase Chain Reaction (PCR) using species-specific primers. 1 µl of dental biofilm from 41 children between 6 and 11 years of age with and without caries was collected and levels of S. dentisani and S. mutans were quantified to determine their proportion regarding the presence or absence of dental caries. Results: 46 samples of dental biofilm were processed. 45.7% belonged to children without caries (NC) and 54.3% with caries (C). It was possible to determine that no children showed good dental hygiene after using the modified Silness and Löe plaque index. Statistically significant differences were found in the count of S. mutans for the NC and C groups (p<0.05), while no significant differences were found in the count of S. dentisani for both groups, but a higher presence of S. dentisani was observed in the NC group. Conclusions: The count of S. mutans increased according to the presence of caries, thus suggesting an important role in the progression of this condition. Even though no significant differences in the frequency of S. dentisani were found in the groups, a tendency in the proportion of such species in the biofilm of children without caries was observed, which might suggest that S. dentisani plays a protective role against cariogenic species like S. mutans.