Date of Award

January 2018

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Oliver R. Oakley

Second Advisor

Marcia M. Pierce

Third Advisor

Malcolm Pratt Frisbie

Abstract

Birth is initiated by a programmed inflammatory response of the placenta and amniotic fluid carried out by maternal and fetal signals, between 37 and 42 weeks gestation for human females. When the inflammatory response occurs off schedule (prior to 37 weeks gestation), pre-term birth is initiated. Pre-term birth is most commonly associated with a maternal infection that consequently leads to infection of the placenta and amniotic fluid; however, the terms of infection are unclear, as microbiota has been discovered in placental membranes and amniotic fluid of healthy pregnancies. The objective of this study is to challenge the sterile womb hypothesis and investigate the relationship between microbiota and negative pregnancy outcomes, specifically pre-term birth. Blood, oral, fecal, uterine, and vaginal samples were collected from 58 postparturient mares by attending veterinarians at Hagyard Equine Institute in Lexington, KY, within 24-36 hours of foaling and before uterine lavage/infusion. Expected due date and date of delivery was noted for birth categorization, pre-term versus full-term. A foal is considered pre-term if born prior to 320 days gestation. Microbiota samples were prepared on sterile nasopharyngeal swabs, which were then used for 16S rRNA gene sequencing on Illumina MiSeq. Sequencing output was analyzed using QIIME 1.9 on VirtualBox. The abundance of Fusobacteria, across all samples, in mares that delivered pre-term (PT) was 2-fold higher than those who delivered full-term (FT). Moreover, Fusobacteria comprised 15% of PT vaginal samples in comparison to 4.9% FT vaginal. Nearly identical ratios are observed in uterine samples of PT and FT deliveries (15.5% and 4.4% respectively). Fusobacteria is a common, nonpathogenic, microbe of the oral cavity but can cause periodontitis in the case of overgrowth. Fusobacterica can also lead to negative pregnancy outcomes if transferred hematogenously through the placenta. However, this is not the case in the PT deliveries of this study, as Fusobacteria did not comprise even one percent of both oral and blood samples. On the other hand, Fusobacteria has been reported in the vaginal microbiome of negative reproductive health and pregnancy outcomes, such as bacterial vaginosis and pre-term births. These results support the hypothesis that vaginal microbiota may vertically ascend through the cervix and into the uterine cavity to proliferate and colonize. We suggest a cross talk occurring between vaginal microbiota and the uterine environment. Whether this interaction always leads to negative outcomes is unclear, though the inflammation of the placenta and amniotic fluid in response to such microbes may be a consequence of their uncontrolled proliferation.

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