23: Antibiotics and betamethasone therapy do not significantly alter the placental microbiome in chorioamnionitis affected pregnancies


      Chorioamnionitis (IAI) is frequently associated with PTB. We have demonstrated that the placenta harbors a unique microbiome and have recently shown that the preterm placental microbiome is distinct and varies based infection. Here, we aimed to examine the differences in the placental microbiome based on clinically indicated therapy (i.e. antibiotics, betamethasone) for preterm birth and IAI.

      Study Design

      This was a cross-sectional analysis of prospectively acquired subject samples from women who delivered between 32-36 weeks. Women who delivered preterm received antibiotics (n=23) and steroids (n=12) as clinically indicated, and all placentas were sent to pathology. Histologic gradation of IAI and funisitis was reported. This resulted in six nested spontaneous birth cohorts (n=9-15 subjects/cohort, Table 1). DNA was extracted from placental swabs collected immediately at delivery and subjected to whole genome shotgun (WGS) metagenomic sequencing. Filtered microbial DNA sequences (150 million/sample) were annotated and analyzed using MG-RAST and R.


      The mean gestational age (GA) for spontaneous preterm infants was 35.1 weeks. We observed different placental microbiome communities among preterm subjects with severe IAI (p=0.07) and with antibiotic treatment (p=0.021). However, we did not find clear differences in the most abundant taxa between preterm subjects that received antibiotic treatment and those that did not (Fig A). Additionally, we found no significant impact on Mycobacterium (p=0.76), Mycoplasma (p=0.89), and Ureaplasma (p=0.52) species. Furthermore, when examining steroid treatment, we found no significant differences in microbial communities (p=0.33) (Fig B).


      Our data support the premise that histologically severe chorioamnionitis is associated with a significantly altered placental microbiome. Interestingly, antibiotic treatment did not significantly further shape nor modify the microbial community in regards to abundant species nor pathologically relevant species. These data suggest that the association of inflammation and spontaneous preterm birth warrants additional investigation, and that the cumulative impact of IAI on the placental microbiome is not amenable to antibiotic therapy.
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