Estudo das comunidades microbianas associadas às infecções endodônticas de dentes decíduos sintomáticos e assintomáticos pelas técnicas do Multiple-Displacement Amplification e Checkerboard DNA-DNA Hybridization

Abstract

Multiple Displacement Amplification (MDA) has been used to uniformly amplify the genome from bacterial species in different types of oral samples. MDA is particularly useful in small samples, since it generates abundant target for microbial analysis. The aim of the present study was to combine MDA and Checkerboard DNA-DNA hybridization to evaluate the microbiota of endodontic infections in deciduous teeth A total of 35 children, 4 to 10 years old, having teeth with intact roots or less than 2/3 of physiological root resorption were involved in this study. Forty root canal samples were collected.and amplified. Amplified samples were analyzed by checkerboard DNA-DNA hybridization for levels of 83 bacterial taxa. . Percentages of teeth colonized by each species at different thresholds in amplified samples were computed. Levels of bacterial species present in different clinical conditions were analyzed. Significance of differences between mean proportions of each species were determined for root canal samples taken from teeth with (open tooth) or without (closed tooth) pulp chamber exposure to oral cavity, sinus tract, swelling, and pain. Significance of differences for each species in these clinical scenarios was sought with Kruskall-Wallis test. The mean amount of DNA (± SD) in the samples prior to amplification was 5.2 (± 4.7) ng. After MDA, samples contained, on average, 6.05 (± 2.3) ìg of DNA. Eighty of 83 DNA probes hybridized with one or more samples. Most prevalent bacterial species at levels > 104 bacterial cells were Actinomyces naeslundii 1 and Prevotella intermedia, both present in 93.8%.of sampled teeth. The mean number of species (± SEM) detected per tooth at the > 104 level was 20.19 (± 3.27).The most commonly detected species at this level were Actinomyces naeslundii 1 and Prevotella intermedia When mean DNA probe counts x 105 (± SEM) were analyzed, the most abundant species were A. naeslundii 1 (17.07±3.17), Prevotella nigrescens (1.12 ± 0.55) and P. intermedia (1.01 ± 0.30). Eikenella corrodens, Haemophilus aphrophilus, and Helicobacter pylori were not detected in any of the samples. Upon the analysis of the microbiota associated with the different clinical signs and symptoms investigated, statistically significant differences could be detected in a few of them. Twenty seven species were statistically significantly increased in the open tooth group. A. naeslundii 1, Veillonella parvula, Gemella morbillorum. Streptococcus oralis, Aggregatibacter actinomycetemcomitans and Neisseria mucosa were statistically significant increased in teeth with pulp chamber exposure to oral cavity. P. intermedia, Neisseria. mucosa, Streptococcus anginosus, Selenomonas noxia and Streptococcus sanguinis were detected in higher mean counts in teeth without sinus tract. There were no statistically significant differences in the microbiota associated with presence or absence of swelling. Painful teeth presented increased counts of Prevotella nigrescens and Prevotella oris. The microbiota associated with root canals from deciduous teeth seems to be more complex than previously anticipated In conclusion, results suggest that selected species are associated with the clinical signs and symptoms detected in primary root canal infections.