Comparative Analysis of the Uterine Microbiome in Canine Pyometra: A 16S rRNA Sequencing Study

Canine pyometra is a prevalent reproductive disorder predominantly affecting older, nulliparous bitches, with peak incidence during the diestrus phase. This condition is frequently complicated by systemic infections and carries high mortality risks. Using 16S rRNA sequencing, this study systematically compared the endometrial microbiota between pyometra-affected dogs (n = 11) and healthy controls (n = 12), revealing significant microbial dysbiosis characterized by pathogenic enrichment and metabolic pathway disruption. Alpha diversity indices (Shannon index: 3.21 vs. 1.89, P < 0.01) confirmed reduced microbial richness in pyometra cases. Taxonomic analysis revealed that Pasteurellaceae, Leptotrichiaceae, and Lactobacillaceae were significantly enriched at the family level, whereas Haemophilus, Lactobacillus, Prevotella, and Fusobacterium predominated at the genus level. LDA effect size (LEfSe) analysis identified Haemophilus and Lactobacillus as microbial biomarkers for pyometra. Functional prediction revealed significant downregulation of metabolic pathways related to nutrient absorption, immune modulation, and xenobiotic degradation, alongside upregulation of membrane transport systems and cellular signaling pathways. Network analysis revealed potential disease associations with butyrate metabolism. These findings provide critical insights for the development of microbiota-targeted therapeutic strategies against canine pyometra.