| dc.description.abstracteng | Early childhood caries is still a worldwide problem that affects children in developing countries as well as children in industrialized nations such as Germany. It is a multifactorial disease, where the main factors are substrate, host, microorganisms and time. In addition, personal factors like oral hygiene and eating habits play an important role as well as oral environmental factors, where genetic factors and saliva characteristics have to be mentioned. Caries is a polymicrobial disease in which numerous different microorganisms are present. The same microorganisms also occur in a healthy condition, but in a different composition.
For this study, a total of 30 children between one and six years of age with early childhood caries had a tongue swab taken from the upper side of the tongue and a saliva sample from the sublingual space. From these samples the DNA of the microorganisms was extracted and the variable region 1-2 of the ribosomal 16S rRNA was amplified and sequenced (MiSeq, Illumina). After bioinformatic data purification 913 OTUs remained, which were used for further analysis. Subsequently, the OTUs were matched against the Human Oral Microbiome Database (HOMD). The 99% similarity was used here as a criterion for species identification. If a sequence could not be clearly assigned, the next higher level was selected for assignment. All sequences with an assignment accuracy of less than 95% were again blasted against the Ribosomal Database Classifier database.
From a total of 60 samples, 57 samples had sufficient quality to be analyzed further. 15 different strains, 27 classes, 50 orders, 95 families, 155 genera and 150 different species could be identified. Among the predominant strains, which were represented in large numbers, are Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria and Fusobacteria. The species that were detected most frequently overall include Gemella haemolysans, Streptococcus sobrinus and Streptococcus mutans.
As a result of this investigation, no differences could be found when comparing the microbiomes of the different ECC types. The initial hypothesis that there are potential differences in the bacterial composition of different ECC types could not be confirmed. Due to the inhomogeneous composition of the investigated cohort it was not possible to obtain a meaningful result in this respect. With regard to the age and sex of the children, no clear trends in the bacterial composition could be detected either.
However, clear differences could be detected when comparing the microbiomes of the tongue and saliva samples, where the tongue samples showed a different microbial composition than the saliva samples. This fact corresponds to the initial assumption that the tongue and saliva microbiomes have different bacterial compositions. OTUs, which were found most frequently in the tongue samples, could be assigned to Rothia mucilaginosa, Haemophilus parainfluenzae and Prevotella pallens. In contrast, OTU8 (Bacteroidetes), Gemella haemolysans and Heamophilus sp. were most frequently detected in the saliva samples. The tongue samples showed a higher diversity than the saliva samples.
In this study, the composition of the microbial community in tongue and saliva samples of different ECC types was investigated for the first time. Significant differences in the microbial composition of tongue and saliva samples were found. However, a different composition of the microbial flora could not be detected in the different ECC types due to the inhomogeneous composition of the investigated cohort.
For future further investigations a larger number of test persons with homogeneous distribution of the three ECC types and a comparison with a control group (healthy test persons) would be recommended. | de |