Alterations and potential roles of microbial population of pregnant mouse saliva and amniotic fluid

Prenatal exposure to intrauterine inflammation (IUI) is a crucial event in PTB pathophysiology. However, the relationship between microflora and PTB is not fully elucidated.In this study, we established an intrauterine inflammation mouse model via LPS intrauterine injection. The saliva and amniotic fluid were collected for 16s RNA gene sequencing. The levels of TNF-α and IL-1β in mouse amniotic fluid were determined by ELISA assays.Up to 60% of the operational taxonomic units (OTUs) in the saliva and amniotic fluid of PBS-treated mice were overlapped. LPS treatment-induced changes in the abundance of oral and amniotic fluid microorganisms. Both immune-associated probiotics, salivarius and mastitidis, were still detected in saliva (at significantly increased levels) after LPS-induced intrauterine inflammation and almost no probiotics of any type were detected in amniotic fluid, suggesting that the uterine cavity seems to be more susceptible to LPS compared to the oral cavity. Moreover, the abundance of pathogenic bacteria Escherichia coli was increased in both saliva and amniotic fluid after LPS treatment. The level of TNF-α and IL-1β in amniotic fluid is positively related to the amniotic fluid E. coli abundance.The microbial composition of saliva and amniotic fluid of pregnant mice was similar. LPS-induced intrauterine inflammation decreased the consistency of microbial composition in mouse saliva and amniotic fluid, increased the abundance of E. coli in saliva and amniotic fluid, and decreased the abundance of immune-associated probiotics, especially in amniotic fluid.