Characterization of the equine placental microbial population in healthy pregnancies

Machteld van Heule; Hugo Fernando Monteiro; Ali Bazzazan; Kirsten Scoggin; Matthew Rolston; Hossam El-Sheikh Ali; Bart C Weimer; Barry Ball; Peter Daels; Pouya Dini

doi:10.1016/j.theriogenology.2023.04.022

Characterization of the equine placental microbial population in healthy pregnancies

Theriogenology. 2023 Aug:206:60-70. doi: 10.1016/j.theriogenology.2023.04.022. Epub 2023 May 2.

Authors

Affiliations

¹ Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA; Department of Morphology, Imaging, Orthopedics, Rehabilitation and Nutrition, Faculty of Veterinary Medicine, University of Ghent, Merelbeke, Belgium.
² Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA.
³ Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, USA.
⁴ Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
⁵ Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis, CA, USA.
⁶ Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA; Theriogenology Department, Faculty of Veterinary Medicine, Mansoura University, Mansoura, Egypt.
⁷ Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA; Department of Population Health and Reproduction, 100K Pathogen Genome Project, School of Veterinary Medicine, University of California, Davis, CA, USA.
⁸ Department of Morphology, Imaging, Orthopedics, Rehabilitation and Nutrition, Faculty of Veterinary Medicine, University of Ghent, Merelbeke, Belgium.
⁹ Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA. Electronic address: pdini@ucdavis.edu.

PMID: 37187056
DOI: 10.1016/j.theriogenology.2023.04.022

Abstract

In spite of controversy, recent studies present evidence that a microbiome is present in the human placenta. However, there is limited information about a potential equine placental microbiome. In the present study, we characterized the microbial population in the equine placenta (chorioallantois) of healthy prepartum (280 days of gestation, n = 6) and postpartum (immediately after foaling, 351 days of gestation, n = 11) mares, using 16S rDNA sequencing (rDNA-seq). In both groups, the majority of bacteria belonged to the phyla Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidota. The five most abundant genera were Bradyrhizobium, an unclassified Pseudonocardiaceae, Acinetobacter, Pantoea, and an unclassified Microbacteriaceae. Alpha diversity (p < 0.05) and beta diversity (p < 0.01) were significantly different between pre- and postpartum samples. Additionally, the abundance of 7 phyla and 55 genera was significantly different between pre- and postpartum samples. These differences suggest an effect of the caudal reproductive tract microbiome on the postpartum placental microbial DNA composition, since the passage of the placenta through the cervix and vagina during normal parturition had a significant influence on the composition of the bacteria found in the placenta when using 16S rDNA-seq. These data support the hypothesis that bacterial DNA is present in healthy equine placentas and opens the possibility for further exploration of the impact of the placental microbiome on fetal development and pregnancy outcome.

Keywords: 16S rDNA; Chorioallantois; Equine; Microbiome; Placenta.

MeSH terms

Animals
Bacteria / genetics
Cervix Uteri
Female
Horses / genetics
Humans
Microbiota* / genetics
Placenta* / microbiology
Postpartum Period
Pregnancy
RNA, Ribosomal, 16S / genetics

Substances

RNA, Ribosomal, 16S