Gut bacterial diversity in bovines infected with Mycobacterium tuberculosis var. bovis: insights on tuberculosis pathogenesis.

Bovine tuberculosis susceptibility and pathogenesis are influenced by host immunity, which may be modulated by the host microbiota. While intestinal microbiota composition affects pulmonary diseases in humans, its role in bovine tuberculosis remains unclear. This study explores the intestinal microbiota of cattle and its association with tuberculosis to better understand disease pathophysiology. A case-control study was conducted using small intestine content samples from cattle with and without tuberculosis, slaughtered in Rio Grande do Sul, Brazil. DNA extraction, 16S rRNA (V4) sequencing, and bioinformatics analyses assessed alpha and beta diversity, taxa characterization, differential abundance, and metabolic pathways. No significant differences in alpha and beta diversities between the groups were detected. However, the Bacillota/Bacteroidota ratio suggested dysbiosis associated with bovine tuberculosis. Differential abundance analysis showed that microorganisms belonging to the Bacillota phylum, the Eubacterium cellulosolvens group, Colidextribacter and Coprococcus genera were enriched in healthy cattle. Conversely, animals with tuberculosis showed higher abundances of Verrucomicrobiota phylum, Sphingomonadaceae and Eubacteriaceae families, and Solobacterium and Clostridia-UCG-014 genera. Moreover, metabolic pathways related to carbohydrate degradation were enriched in healthy animals, and biosynthetic pathways related to disease were enriched in tuberculosis animals. This study highlights associations between intestinal microbiota and bovine tuberculosis, providing insights into disease mechanisms.