Kakiora, Violeta; (2022) How do changes in the environment alter the oral microbiome of adolescents. Doctoral thesis (D.Dent), UCL (University College London).

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Abstract

Introduction The oral cavity is one of the most complex and diverse microbial habitats across the human body. The oral microbiome is a causative factor in conditions such as dental caries and periodontal disease but can have a significant role in the pathogenesis of nonoral diseases. The composition of the human oral microbiome is affected by multiple factors, including the environment and host genetics. Previous studies have demonstrated that environmental effects have dominated over genetic effects, with shared household having a significant effect on the microbial composition. Furthermore, the establishment of the salivary microbiome early in life affects its long-term composition. Aims and objectives The aim of this study is to analyse the oral microbiome composition of adolescents and investigate the diversity of the bacterial communities in depth of time. Additionally, to determine whether the oral bacterial community is stable in adolescents and how the shared school environment may influence the oral microbiome composition of boarder students. Methods and materials Saliva samples were collected from 17 participants at nine time points within one academic year. Participants of this study are students of a boarding school. The age range was from 11 to 16 years. Students were divided in two groups according to their boarding status: boarders and non-boarders. A total of 135 saliva samples were collected and analysed. Microbial composition of saliva was assessed by sequencing all the variable regions (V1-V9) of the 16S rRNA gene. Results Five major phyla predominated in both groups; Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes, Fusobacteria, forming 99.37% of the total phyla observed. Taxonomic analysis at genus level revealed that Rothia was the most abundant genera, followed by Streptococcus, Neisseria, Haemophilus and Prevotella. The most abundant species identified within all the participants and all sampling points is Rothia mucilaginosa, Streptococcus oralis and Haemophilus parainfluenzae. Boarders had significantly higher alpha diversity compared to the group of non-boarder group. The beta diversity of the boarder group revealed no clear trend on the similarity of the oral microbiome, which could indicate that boarders share a more similar oral microbiome composition. However, it was noted that having spent more days at school, the oral microbiome composition of boarder students tends to become more similar. Conclusion This study concluded that the oral microbiome of adolescents does not remain stable within the studied period of one academic year and that shared environment may have an important role in the shaping of the oral microbiome of adolescents. However, there is a need for further studies involving larger population, equal number of participants in each group and longer sampling time, in order to determine more accurately the effect of shared environment in the composition of the oral microbiome of adolescents.

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