A Novel Benzoxaborole Is Active against Escherichia coli and Binds to FabI.

To combat the looming crisis of antimicrobial-resistant infections, there is an urgent need for novel antimicrobial discovery and drug target identification. The benzoxaborole series was previously identified as an inhibitor of mycobacterial growth. Here, we demonstrate that a benzoxaborole is also active against the Gram-negative bacterium Escherichia coli in vitro. We isolated resistant mutants of E. coli and subjected them to whole-genome sequencing. We found mutations in the enoyl acyl carrier protein FabI. Mutations mapped around the active center site located close to the cofactor binding site. This site partially overlaps with the binding pocket of triclosan, a known FabI inhibitor. Similar to triclosan, the physical interaction of the benzoxaborole with FabI was dependent on the cofactor NAD+. Identification of the putative target of this compound in E. coli provides scope for further development and optimization of this series for Gram-negative pathogens.