PSV-7 The reproductive tract microbiota of cyclic and pregnant gilts.

Abstract The composition of bacterial communities within the female reproductive tract has been associated with fertility status in mammals; however, limited research has explored reproductive tract microbiota in swine. The objective of this study was to analyze the abundance and diversity of bacterial communities from the mucosal surface of the vagina, cervix, uterus, and chorioallantois, and within the allantoic and amniotic fluids throughout gestation in gilts. Duroc x Landrace x Yorkshire gilts (n=38) free of physical, health or reproductive-related issues were euthanized and hysterectomized on either day 11 (n = 11; peri-implantation), 15 (n = 10; implantation), 60 (n =6; mid-gestation) or 90 (n = 6; late-gestation) of pregnancy, as well as day 15 (n = 5; cyclic) of the estrous cycle. Bacterial analyses were conducted targeting the V4 hypervariable region of the 16S rRNA gene. In day 15 cyclic gilts, genera Campylobacter, Actinobacillus, Anaerococcus, and Fusobacterium were more abundant in the vagina than in the cervix (P < 0.05). Additionally, Campylobacter, Porphyromonas, and Anaerococcus were more abundant in the vagina than in the endometrium (P < 0.05). In pregnant gilts, the genus Fusobacteria abundance was greater in the vagina than in the cervix and endometrium on days 11 (P < 0.01) and 15 (P < 0.01) of gestation. Additionally, Lactobacillus was more abundant in allantoic fluid than the endometrium on day 60 (P < 0.05). Further, Streptococcus, Campylobacter, and Actinobacillus were more abundant in the vagina than in the amniotic fluid on day 90 (P < 0.05). Alpha diversity metrics indicated lower microbial diversity in amniotic fluid relative to other tissues (P < 0.05). However, alpha diversity did not differ between cyclic and pregnant gilts (P > 0.05). Beta diversity analysis revealed distinct clustering patterns based on tissue type and stage of pregnancy. Specifically, the vagina, cervix, and endometrium clustered separately from placental fluids. Additionally, microbial communities in samples from day 15 cyclic, day 11 pregnant, and day 15 pregnant gilts clustered distinctly from days 60 and 90 of gestation (P < 0.01). These findings suggest that microbial communities within the reproductive tract are dynamic and vary by both anatomical location and stage of pregnancy or estrous cycle. The distinct clustering of microbial populations between early and late stages of gestation indicates shifts in bacterial composition potentially associated with the presence of a conceptus. Additionally, the observed differences in microbial diversity across reproductive tissues and fetal fluids highlight potential functional roles of microbiota in reproductive success.