Efficacy of β-lactam/β-lactamase inhibitor combination is linked to WhiB4-mediated changes in redox physiology of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) expresses a broad-spectrum beta-lactamase (BlaC) that mediates resistance to one of the highly effective antibacterials, beta-lactams. Nonetheless, beta-lactams showed mycobactericidal activity in combination with beta-lactamase inhibitor, clavulanate (Clay). However, the mechanistic aspects of how Mtb responds to beta-lactams such as Amoxicillin in combination with Clay (referred as Augmentin [AG]) are not clear. Here, we identified cytoplasmic redox potential and intracellular redox sensor, WhiB4, as key determinants of mycobacterial resistance against AG. Using computer-based, biochemical, redox-biosensor, and genetic strategies, we uncovered a functional linkage between specific determinants of beta-lactam resistance (e.g. beta-lactamase) and redox potential in Mtb. We also describe the role of WhiB4 in coordinating the activity of beta-lactamase in a redox-dependent manner to tolerate AG. Disruption of WhiB4 enhances AG tolerance, whereas overexpression potentiates AG activity against drug-resistant Mtb. Our findings suggest that AG can be exploited to diminish drug-resistance in Mtb through redox-based interventions.