Genetic Determinants of Rifabutin Susceptibility in Multidrug-Resistant Tuberculosis: Insights from Whole-Genome Sequencing

Multidrug-resistant tuberculosis (MDR-TB) is a critical global health threat. Rifabutin (RFB) is active against some rifampicin (RIF)-resistant Mycobacterium tuberculosis strains, but genetic markers guiding RFB use remain unclear. This study aimed to identify determinants of RFB susceptibility using whole-genome sequencing (WGS) and Minimum inhibitory concentrations (MICs) testing. MICs for RFB were determined by broth microdilution according to CLSI M24–A2 guidelines (susceptibility defined as MIC < 0.5 µg/mL) for 183 MDR-TB isolates from Shenzhen, China. Associations of rpoB mutations, lineage, and compensatory mutations with log2 transformed RFB MIC were assessed using Kruskal-Wallis tests, Fisher’s exact tests, and multivariable linear regression models. rpoB mutation type was the primary determinant of RFB susceptibility. D435V was consistently associated with preserved RFB susceptibility, with 66.7