Tuberculosis (TB), caused by Mycobacterium tuberculosis complex (MTBC) pathogens, remains a global health threat. While bacterial genetic adaptations during host infection are poorly understood, phase variation in genomic homopolymeric tracts (HT) may drive pathogenicity evolution. Here, we demonstrate that M. bovis exploits HT insertion mutations in the fumarate reductase-encoding frd operon to subvert host immunometabolism. In macrophages, wild-type M. bovis secretes FRD-catalyzed succinate, stabilizing hypoxia-inducible factor-1α (HIF-1α) to drive glycolytic reprogramming and IL-1β production. This activates IL-1R-dependent Th1 immunity, restraining bacterial replication. Conversely, M. bovis frd HT insertion mutants impair succinate secretion, suppressing HIF-1α/IL-1β signaling and redirecting immunity toward pathogenic Th17 responses that promote neutrophil infiltration and tissue necrosis. Mice infection models reveal that M. bovis frd mutants exhibit enhanced pathogenicity, with higher pulmonary bacterial burdens. IL-1R blockade phenocopies frd HT insertion mutation effects, exacerbating lung pathology. Crucially, conserved frd HT polymorphisms in clinical M. tb isolates suggest shared immune evasion strategies across MTBC pathogens. Our work uncovers the bacterial gene phase variation mechanism of hijacking the succinate/HIF-1α/IL-1β axis to operate host immunity, providing a framework for targeting host metabolic checkpoints in TB therapy.

Background: Glycerol kinase (glpK) is essential for the first step of glycerol catabolism in Mycobacterium tuberculosis. However, Mycobacterium bovis has been known to grow poorly in glycerol media because of a base insertion in the glpK gene. Methods: We analyzed the glpK gene sequences of 60 clinical M. bovis isolates, and determined the minimum inhibitory concentration of 14 drugs by microdilution method to evaluate the effect of frameshift mutations on drug sensitivity. The effect of M. bovis growth rate on its drug sensitivity was investigated using bacteria grown on glycerol or pyruvate. Results: A total of 44 (73.33%) clinical M. bovis isolates have frameshift mutations in a homopolymeric tract of 7 cytosines in the glpK gene. 15.00% M. bovis isolates showed phenotypic drug resistance. Glycerol metabolism-deficient M. bovis showed reduced susceptibility to 9 out of 14 tested drugs. Mutations in the glpK gene can lead to impaired growth in glycerol-based media, while the minimal inhibitory concentration values of slow-growing M. bovis were higher. Conclusion: Mutations in the glpK gene can lead to slowed growth and reduced susceptibility to drugs in M. bovis, which may contribute to the emergence of drug-resistant M. bovis and pose a threat to human health owing to the zoonotic capacity of M. bovis.

The diagnosis of drug‐resistant tuberculosis (TB) by molecular testing of Mycobacterium tuberculosis drug resistance genes is becoming increasingly common clinically. However, M. bovis, as an uncommon pathogen of human TB, may interfere with the test results. A comprehensive understanding of phylogenetically informative mutations in the drug resistance genes of M. bovis is required to distinguish true resistance‐conferring mutations. We analyzed 53 drug resistance genes in 165 M. bovis isolated from humans using whole‐genome sequencing data and found that 98.2% (162/165) of isolates have pyrazinamide intrinsic genotypic resistance, owing to the H57D mutation in the pncA gene. 12.1% (20/165) of M. bovis isolates were resistant to drugs other than pyrazinamide. Furthermore, we discovered 18 phylogenetically informative mutations that differed between M. bovis and the major lineages 1–4 of M. tuberculosis. Additionally, we reported false‐positive ethambutol resistance caused by M. bovis infection due to the phylogenetically informative mutation embB E378A. This study is crucial for gaining insights into the genetic characterization and drug resistance of M. bovis prevalent in humans, as well as contributing to the development of more accurate molecular diagnostic methods and detection tools for drug resistance.

Type II toxin–antitoxin (TA) systems are significantly expanded in the Mycobacterium tuberculosis complex; however, the functional role of the VapBC40 system in Mycobacterium bovis (M. bovis) pathogenesis remains poorly characterized. This study aimed to investigate the role of VapBC40 in mycobacterial virulence and evaluate its potential as a target for rational vaccine attenuation. We performed evolutionary analysis and yeast two-hybrid assays to characterize VapBC40 system specificity, conducted in vitro macrophage infection models and in vivo murine studies to assess virulence contribution, and evaluated the immunoprotective efficacy of a VapC40 knockout strain. Evolutionary analysis revealed progressive sequence conservation and stringent homologous pairing specificity within the VapBC40 system. The VapC40 toxin correlates with enhanced intracellular bacterial survival, increased host cell death, and more severe pulmonary pathology with systemic dissemination. Based on these findings, we evaluated the vaccine potential of a vapC40 knockout strain. Immunization with this attenuated strain elicited a Th1 cellular immune response, characterized by enhanced IFN-γ production and increased frequency of CD4⁺IFN-γ⁺ T cells. Upon challenge with virulent M. bovis, the knockout strain conferred superior protection compared to the conventional BCG vaccine, significantly reducing lung pathology and restricting extrapulmonary bacterial dissemination. Although the molecular mechanisms underlying VapC40-mediated effects remain to be fully elucidated, our findings suggest an important role of the VapBC40 system in mycobacterial-host interactions and support its potential as a target for next-generation tuberculosis vaccine development.