Oral Microbiome Composition and Pre-Term Birth Incidence

Objectives: Periodontitis has been associated with pre-term birth in several studies. A suggested explanation of this involves the translocation of oral bacteria to the amniotic fluid, which has been demonstrated in one clinical case.
The aim of this study was to determine if oral microbiome composition influenced pre-term birth.
Methods: The study cohort comprised 180 subjects, selected from a larger group to have equal numbers of term and pre-term births. Within 3 months of delivery, the Modified Gingival Index, Quigley and Hein plaque indices and a full-mouth periodontal assessment were recorded and samples of plaque and saliva collected. V1-V2 variable regions of the 16S rRNA genes were PCR-amplified from each sample and sequenced by Illumina MiSeq. The sequences were quality-filtered using the DADA2 R package, clustered to 98.5% similarity OTUs by mothur and classified with reference to the Human Oral Microbiome Database. The diversity within samples was estimated as mean inverse Simpson index over 1000 subsampling replicas of 5189 sequences each. The same subsampling approach was applied to calculate a theta-YC dissimilarity matrix between samples.
Results: The samples were dominated by the genera Streptococcus (saliva 29%, plaque 12%) Prevotella (13%, 9%), Leptotrichia (3%, 15%) and Fusobacterium (3%, 12%). No significant differences were found in richness or diversity of saliva and plaque bacterial communities (Wilcoxon test) nor in OTU composition (AMOVA) between term and pre-term groups. Moreover, no significant association was found between periodontal disease and pre-term birth in these subjects.
Conclusions: In conclusion, this study found no relationship between pre-term birth and oral microbiome composition.