Molecular Characterization of the Mycobacterium tuberculosis Complex in Humans and Cattle.

BACKGROUND/

OBJECTIVES

Zoonotic tuberculosis (TB) remains a persistent public health challenge worldwide. It is particularly common in settings with close human-livestock-environment interactions. In Tanzania, progress toward TB control is increasingly threatened by multidrug-resistant tuberculosis (MDR-TB), yet genomic data from regions characterized by pastoralist and mining activities remain scarce. This study employed whole-genome sequencing (WGS) to characterize M. tuberculosis complex (MTBC) strains circulating among human and cattle populations in the Manyara region of northern Tanzania, with a focus on resistance-associated mutations and phylogenetic relationships.

METHODS

This cross-sectional study was conducted between September 2024 and February 2025. A total of 178 presumptive human TB cases provided sputum samples. From cattle, 161 samples were collected (110 milk samples and 51 lymph node aspirates), with each animal contributing only one type of sample. Specimen were analyzed using GeneXpert MTB/RIF, Lowenstein-Jensen culture, and WGS. Phylogenetic reconstruction was performed using SNP-based methods and IQ-TREE2 version 2.2.0.

RESULTS

Among human participants, 14 (7.8%) sputum samples were GeneXpert positive and were confirmed as members of MTBC by LJ culture. In cattle, one (0.62%) lymph node aspirate was positive for MTBC. Significant predictors of MTBC positivity included previous TB history, weight loss, and occupation involving mining and cattle keeping. WGS of five human isolates identified Lineages 1, 3, and 4. One isolate (Sample 98) harbored mutations associated with XDR-TB.

CONCLUSIONS

WGS revealed M. tuberculosis Lineages 1, 3 and 4 circulating in the Manyara region, with diverse genetic mutations conferring with resistance to first- and second-line anti-TB drugs. These findings highlight the importance of integrated genomic surveillance to monitor drug resistance patterns in Tanzania and similar settings across human and animal populations.