Genomic diversity of human-associated Mycobacterium bovis in Canada

ABSTRACT Human infections caused by Mycobacterium bovis in Canada are not well documented. The following study analyzed M. bovis (excluding BCG) isolates identified in public health laboratories across Canadian provinces between 2000 and 2025. Whole-genome sequencing was used to catalog mutations linked to antimicrobial resistance and evaluate the genomic relatedness of isolates. The majority of samples in this study were non-respiratory (60%). Of 74 study isolates, 69 (93%) were phenotypically sensitive to first-line drugs isoniazid, rifampin, and ethambutol. The most frequently encountered M. bovis clusters belonged to M. tuberculosis complex lineages La 1.7 and La 1.8. Although some isolates showed phylogenetic clustering, their lack of spatial and temporal relatedness suggested sporadic cases rather than local M. bovis transmission. Of all first-line drugs evaluated, isoniazid showed the lowest concordance (94.4%) between phenotypic and genotypic methods. The isolates in this study harbor some mutations that are not currently documented in the WHO mutation catalog, indicating that these variants may be rare. The findings suggest that the prevalence of M. bovis infection in Canada is low with cases unlikely to be acquired through human-to-human transmission. IMPORTANCE Incidence of human infections due to Mycobacterium bovis in Canada is largely unknown as these data are not collected or annually published. This research is a first effort to identify historical M. bovis isolates that were available for culture, had drug susceptibility testing data, and were analyzed through whole-genome sequencing. The annual reporting of these data in Canada holds value.