Metagenetic Analysis of the Pregnant Microbiome in Horses.
Authors: Beckers Kalie F, Gomes Viviane C L, Crissman Kassandra R, Liu Chin-Chi, Schulz Christopher J, Childers Gary W, Sones Jenny L
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Metagenetic Analysis of the Pregnant Microbiome in Horses Placentitis remains the leading infectious cause of abortion in mares and can severely compromise foetal growth and neonatal viability, yet the microbial mechanisms underlying non-ascending forms—such as nocardioform placentitis—remain poorly characterised. Beckers and colleagues used 16S rRNA gene sequencing (V4 region) to profile bacterial communities across oral, vaginal, faecal, and placental tissues collected from five pregnant mares at 96–120 days of gestation, establishing baseline microbiome composition in early pregnancy. The placental microbiota demonstrated significant compositional differences from all other body sites (Bray-Curtis dissimilarity), with notably lower alpha diversity (richness and evenness) compared to faeces, whilst sharing greater similarity with oral cavity bacteria—a finding with potentially important implications for pathogenic translocation routes. Faecal samples exhibited the highest bacterial diversity, whereas both placental and oral cavities showed the most restricted communities, suggesting distinct selective pressures or barriers at these sites. These results indicate that the equine placenta hosts a resident microbiome distinct from systemic and mucosal sites, and the observed similarities between placental and oral bacterial profiles warrant investigation into whether oral bacteria may translocate to placental tissues and contribute to polymicrobial placentitis, potentially redefining our understanding of infection pathways beyond the traditionally recognised ascending vaginal route.
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Practical Takeaways
- •Understanding that the pregnant mare's placenta harbors its own distinct microbiome may help veterinarians develop better diagnostic and preventive strategies for placentitis
- •The similarity between placental and oral microbiota suggests oral health in pregnant mares warrants attention as a potential source of placental infection
- •Early gestation microbiome characterization provides baseline data to help identify pathologic changes associated with placentitis in future research
Key Findings
- •Placental microbiome is significantly distinct from fecal, oral, and vaginal microbiomes in pregnant mares at 96-120 days gestation (Bray-Curtis dissimilarity p<0.05)
- •Fecal microbiota showed greatest alpha diversity (Shannon index), while oral cavity and placenta had least diversity
- •Placental microbial communities show greater similarity to oral cavity than to vaginal or fecal sites, suggesting potential bacterial translocation route