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Title: Studies on subgingival microbiota of chronic periodontitis in the presence or absence of type 2 diabetes mellitus
Author: Liu, L. S.
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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Periodontitis (PD) has been reported as the sixth complication of diabetes (DM) and a bi-directional relationship has been suggested for both diseases. Currently there is no conclusive evidence on the subgingival microbial composition in the presence of DM on PD patients. The aim of this thesis is to investigate and describe any differences between the subgingival microbiota of DM and non-DM (NDM) subjects as well as the effect of periodontal therapy on the subgingival microbiota of type 2 DM (T2D) subjects over 12 months with the use of next-generation sequencing. These analyses may generate further information to previous studies that targeted a limited amount of bacteria when investigating the microbiological link between the association of diabetes mellitus and periodontal disease. This PhD thesis is based on: 1) A systematic review of the literature on differences of the sub-gingival plaque between the T2D-PD (diabetes-periodontitis) and non-T2D-PD subjects, 2) A study aiming at describing and comparing the subgingival microbiota of (n=60) healthy (H) and (n=60) chronic severe periodontitis (PD) subjects. 3) A study aiming at describing the subgingival microbiota of a cohort (n=120) of T2D-PD patients. 4) A study aiming at comparing the changes of the subgingival microbiota of 120 T2D-PD patients (60 control and 60 test; C and T) following periodontal treatment at 6 and 12 months. 5) A secondary analysis of studies aiming at investigating the effect of smoking status on the subgingival microbiota of H, PD and/ or T2D-PD patients. For all studies, Illumina MiSeq next-generation sequencing platform was used to observe the microbial profile by targeting the 16S rRNA V5-7 hypervariable region to provide a broader picture of the microbiome under different conditions. Results: 1) A general decreasing trend of Tannerella forthysia in T2D-PD versus non-T2D-PD patients was found in the systematic review. 2) Increased mean relative abundance (RA) in periodontal pathogens such as genera Porphyromonas, Filifactor and other bacteria were found in PD when versus H. 3) Taxa under phylum Firmicutes class Clostridia were the main constituents of the T2D-PD bacteria, with an increased RA of genera Oribacterium, Megasphaera, Selenomonas, Filifactor, Veillonella and Peptostreptococcus predicting the poor versus good T2D group. 4) A decreasing trend in the periodontal pathogens in T versus C in the T2D-PD study at both 6 and 12 months was found, with high RA of Porphyromonas consistently occurring in control. 5) The smoking status was shown to affect the subgingival microbiome. The main conclusion is that periodontal therapy in T2D-PD subjects helps to reduce the RA of Porphyromonas, Parvimonas, Pseudoramibacter-Eubacterium and Treponema 6 and 12 months following treatment, while it increased the RA of Cardiobacterium and Oribacterium. The difference in the subgingival microbiome between T2D-PD and non-T2D-PD has also been established, showing the effect of T2 D-PD on the subgingival microbiome.
Supervisor: Donos, N. ; Spratt, D. ; Gkranias, N. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available