关键词: 流产, 阴道菌群, 高通量测序, 功能预测, 细菌分离鉴定

Abstract:

The aim of this experiment was to investigate the differences in the vaginal and intestinal flora structure of mares affected by abortion, and to isolate and identify vaginal pathogens and explore the biological characteristics of vaginal pathogens responsible for equine abortion. Vaginal secretion and faecal samples were collected from 10 mares in the aborted mare group and 6 mares in the healthy group. High-throughput sequencing of vaginal and faecal samples was performed in the V3-V4 region of the 16S rRNA to compare the differences in the vaginal and intestinal flora between the two groups, and to isolate and identify the vaginal bacteria in the aborted mares. Alpha diversity showed a trend of increased vaginal and intestinal flora richness and diversity in the aborted group compared with the healthy group. The similarity, dispersion, abundance and evolutionary relationship of the vaginal and intestinal flora of the two groups were found to be different by both Binary jaccard and unweighted unifrac distance matrix analyses. At the phylum level, compared with the healthy group, the vaginal flora of the abortion group showed a decrease in the abundance of Anaplasma and Clostridium phyla and an increase in the abundance of Helicobacter phyla and Thick-walled phyla, while the intestinal flora of the abortion group showed a decrease in the abundance of Thick-walled phyla and Anaplasma phyla, and an increase in the abundance of Aspergillus phyla and Actinobacterium phyla. LEfSe analysed Lactobacillaceae, Lactobacillus, Enterobacterales, Enterobacteriaceae, and Fusarium as the dominant vaginal flora species in the abortion group; and Actinomyces, Actinobacteria, Actinomycetia, Corynebacteriaceae, Corynebacterium, Peptoniphilus, and Peptinophilae were the dominant intestinal species in the abortion group, and the altered abundance of these bacteria may be correlated with the development of the disease, as well as with the prognosis. Functional prediction and correlation analyses revealed a positive correlation between normal vaginal bacteria and health-related microorganisms. Normal vaginal microbes were negatively correlated with abortion-associated pathogens. Metabolic pathways in the gut of aborted mares were highly correlated with vaginal disease pathways, and immune disease pathways in the gut were positively correlated with changes in the vaginal immune system, suggesting that metabolic dysfunction in the gut may trigger the development of certain vaginal diseases. Four main pathogenic bacteria were isolated and identified from the vagina of aborted mares: Salmonella, Streptococcus equi subspecies zoonoticus, Klebsiella and Escherichia coli. Vaginal and intestinal flora of mares are highly involved in the process of abortive disease and immunity, and the metabolic pathways of the flora may play a role in bridging the intestinal and vaginal flora and host immunity at the time of gestation, with the phyla Thick-walled and Actinobacteria in the vaginal flora and the phyla Arcanobacterium hippocoleae and Streptococcus infantarius were negatively correlated with the abortion-associated Aspergillus phylum. Salmonella may be the main causative agent of equine abortion and that Aspergillus phylum, Peptostreptococcus spp. and Campylobacter spp. may be the vaginal flora biomarkers for the occurrence of abortion.

Key words: abortion, vaginal flora, high-throughput sequencing, functional prediction, bacterial isolation and identification