Investigation of the contribution of oral bacterial microbiota to health and disease in a South African cohort.

Date
2024-02
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Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Background: Metabolic syndrome (MetS) is a worldwide epidemic. Risk factors for MetS include diet and lifestyle, as well as genetic predisposition; however, evidence suggests that disruption of the oral microbiota is an important emerging risk factor for MetS. Additionally, periodontal disease (PD) is more prevalent in individuals with MetS and both conditions are associated with inflammation and insulin resistance. Porphyromonas gingivalis has been linked to PD which may be a marker for MetS. The aim of the study was to compare the microbial diversity of subgingival plaque of individuals with MetS and PD to that of healthy individuals, and to determine the abundance of P. gingivalis in the oral cavity of individuals with and without PD. An additional aim was to compare amplicon sequencing to quantitative PCR of P. gingivalis in individuals with PD. Methods: Subgingival plaque samples were obtained from 119 individuals from the mixed ancestral community in Bellville South, Western Cape. Individuals were classified as having MetS and/or PD using standardised criteria. Illumina sequencing of the V3-V4 hypervariable region of the 16S rRNA gene was performed and sequences were clustered into operational taxonomic units based on 97% similarity, using the Human Oral Microbiome Database. Microbial community profiles of healthy and diseased groups were compared using alpha and beta diversity measures. Additionally, P. gingivalis DNA in dental plaque was quantified by a SYBR green based real-time quantitative polymerase chain reaction (qPCR). Results: There were no significant differences in microbial community composition or diversity between individuals with and without MetS and between those with PD and controls. No statistically significant health-associated and PD associated OTUs were identified. Only one OTU, classified Peptostreptococcaceae (XIII) (G-1), was significantly more abundant in the MetS group. The real-time qPCR results showed similar levels of P. gingivalis detected in healthy individuals and those with PD. Higher P. gingivalis levels were observed in the severe PD group, however, the sample set was too small to determine adequate statistical differences. Conclusions: The findings suggest that factors (such as lifestyle, environment, and host immunity) other than genus-level oral microbial community composition may be responsible for the progression of MetS or PD in the Bellville South community. The study was limited to small sample sets and therefore, subtle differences in the microbial community may not have been detected. Furthermore, a larger study could reveal the role Peptostreptococcaceae plays in metabolic syndrome. P. gingivalis was not an indicator for PD, but may be an indicator of severe PD. Further investigation is needed regarding the role that other periodontal pathogens, as well as bacterial abundance, play in the initiation and progression of PD.
AFRIKAANSE OPSOMMING: Agtergrond: Metaboliese sindroom (MetS) is 'n wêreldwye epidemie. Risikofaktore vir MetS sluit dieet, lewenstyl en genetiese predisposisie in. Ontwrigting van die orale mikrobioom is as 'n belangrike opkomende risikofaktor vir MetS geïdentifiseer. Bykomend is periodontale siekte (PS) ook meer algemeen in individue met metaboliese sindroom en beide toestande word geassosieer met inflammasie en insulien weerstandigheid. Porphyromonas gingivalis, wat gekoppel is aan periodontale siekte, kan 'n merker vir MetS wees. Die doel van hierdie studie was om die mikrobiese diversiteit van subgingivale plaak in individue met MetS en periodontale siekte te vergelyk met dié van gesonde individue. Die oorvloedigheid van P. gingivalis in die mondholtes van individue met en sonder periodontale siekte is ook bepaal. Metodes: Subgingivale plaakmonsters is verkry van 120 individue van die gemengde-ras gemeenskap in Bellville-Suid, Wes-Kaap. Individue is geklassifiseer volgens MetS en / of periodontale siekte volgens gestandaardiseerde kriteria. P. gingivalis-DNS in tandplaak is gekwantifiseer deur 'n SYBR-groen-gebaseerde qPKR. Illumina-DNS-volgordebepaling van die V3-V4 hiperveranderlike gebied van die 16S rRNS-gene is uitgevoer en volgordes met 97% ooreenkomstigheid is saamgevoeg in operasionele taksonomiese eenhede (OTUs) met behulp van die “Human Oral Microbiome Database”. Mikrobiese gemeenskaps-profiele van gesonde- en siekte groepe is vergelyk met behulp van alfa- en beta-diversiteitsmaatreëls. Resultate: 'n Totaal van 5 117 285 volgordes was beskikbaar nadat PKR- en volgordebepalingsfoute met behulp van die mothur-pyplyn verwyder was. Die meerderheid van die OTUs het behoort aan die phyla Firmicutes (22.4%), gevolg deur Bacteroidetes (14.6%), Fusobacterium (12.4%) en Proteobacteria (3.4%). Die mees oorvleodigste genera in beide groepe was Prevotella (14.50%), Leptotrichia (13.66%), Veillonella (13.42%), Selenomonas (9.07%), Fusobacterium (7.49%) en Streptococcus (6.81%). Wat mikrobiese gemeenskaps-samestelling en diversiteit betref, was daar geen beduidende verskille opgemerk tussen individue met en sonder MetS en tussen diegene met PS en hul kontroles nie. Geen statistiese beduidende gesondheidsverwante of periodontale siekte verwante OTU's is geïdentifiseer nie. Slegs een OTU, geklassifiseer as Peptostreptococcaceae (XIII) (G-1), het ‘n verwantskap met die MetS-groep getoon. Die qPKRresultate het soortgelyke vlakke van P. gingivalis getoon in gesonde individue en diegene met PS. Hoër vlakke van P. gingivalis was opgemerk in individue met erge PS, maar die steekproefstel was te klein om voldoende statistiese verskille te bepaal. Gevolgtrekkings: Die bevindings dui daarop dat faktore (soos lewenstyl, omgewing en immuniteit), bo en behalwe genera-vlak orale mikrobiese gemeenskaps-samestelling, verantwoordelik kan wees vir die progressie tot MetS of PS in die Bellville-Suid gemeenskap. Die grootte van die studie is beperk en subtiele verskille in die mikrobiese gemeenskap kon dus nie aangetoon word nie. Alhoewel P. gingivalis nie per se as ‘n aanwyser vir PS beskou kan word nie, kan dit wel dui op die teenwoordigheid van ernstige PS. Verdere navorsing word benodig in die gebied van periodontale patogene en bakteriele oorvloedigheid en die rol in die ontwikkeling van PS.
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Thesis (MSc)--Stellenbosch University, 2024.
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