Evolution of Mycobacterium tuberculosis transcription regulation is associated with increased transmission and drug resistance.

Mycobacterium tuberculosis (Mtb) has co-evolved with humans for thousands of years and is characterized by variation in virulence, transmissibility, and disease phenotypes. To identify bacterial contributors to phenotypic diversity, we developed new RNA sequencing (RNA-seq) and phylogenomic tools to capture hundreds of Mtb isolate transcriptomes, link transcriptional and genetic variation, and find associations between variants and epidemiologic traits. Across 274 Mtb clinical isolates, we uncovered unexpected diversity in virulence gene expression, which we linked to known and unknown regulators. Surprisingly, we found that many isolates harbor variants associated with decreased expression of EsxA (Esat6) and EsxB (Cfp10), which are virulence effectors, dominant T cell antigens, and immunodiagnostic targets. Across >55,000 isolates, these variants associate with increased transmissibility, especially in drug-resistant Mtb strains. Our data suggest expression of Mtb virulence genes is evolving in response to drug-linked pressure, raising concerns about use of these targets in immunodiagnostics and next-generation vaccines.