RT Journal Article SR Electronic T1 Efficacy of the β-lactam\β-lactamase inhibitor combination is linked to WhiB4 mediated changes in redox physiology of Mycobacterium tuberculosis JF bioRxiv FD Cold Spring Harbor Laboratory SP 103028 DO 10.1101/103028 A1 Saurabh Mishra A1 Prashant Shukla A1 Ashima Bhaskar A1 Kushi Anand A1 Priyanka Baloni A1 Rajeev Kumar Jha A1 Abhilash Mohan A1 Raju S. Rajmani A1 V. Nagaraja A1 Nagasuma Chandra A1 Amit Singh YR 2017 UL http://biorxiv.org/content/early/2017/01/30/103028.abstract AB Aims Inhibition of β-lactamase by clavulanate (Clav) sensitizes multi-and extensively drug-resistant Mycobacterium tuberculosis (Mtb) strains towards β-lactams such as amoxicillin (Amox). However, the underlying mechanism of how Mtb responds to Amox-Clav combination (Augmentin; AG) is not characterized.Results We integrated global expression profiling with the protein-protein interaction landscape and generated a genome-scale network of Mtb in response to AG. In addition to specific targets (e.g., peptidoglycan biosynthesis and β-lactamase), the response to AG was also centered on redox-balance, central carbon metabolism (CCM), and respiration in Mtb. We discovered that AG modulates superoxide levels, NADH/NAD+ balance and mycothiol redox potential (EMSH) of Mtb. Higher intra-mycobacterial EMSH potentiates mycobactericidal efficacy of AG, whereas lower EMSH induces tolerance. Further, Mtb responds to AG via a redox-sensitive transcription factor, WhiB4. MtbΔwhiB4 displayed higher expression of genes involved in β-lactam resistance along with those mediating respiration, CCM and redox balance. Moreimportantly, WhiB4 binds to the promoter regions and represses transcription of genes involved in β-lactamase expression in a redox-dependent manner. Lastly, while MtbΔwhiB4 maintained internal EMSH, exhibited greater β-lactamase activity and displayed AG-tolerance, overexpression of WhiB4 induced oxidative shift in EMSH and repressed β-lactamase activity to aggravate AG-mediated killing of drug-sensitive and –resistant strains of Mtb.Innovation and Conclusions This work demonstrate that efficacy of β-lactam\β-lactamase inhibitor combination can be attenuated by elevating mycobacterial antioxidant capabilities and potentiated by impairing redox buffering capacity of Mtb. The functional linkage between β-lactams, redox balance, and WhiB4 can be exploited to potentiate AG action against drug-resistant Mtb.