trans -Translation inhibitors that kill M. tuberculosis and pathogenic Non-tuberculous Mycobacteria have a dual mechanism of action

ABSTRACT Mycobacterium tuberculosis and pathogenic nontuberculous mycobacteria pose a growing challenge to human health, and new antibiotics that target new pathways with novel mechanisms of action are urgently needed. Acylaminooxadiazole derivatives have previously been shown to inhibit the trans- translation ribosome rescue pathway and kill M. tuberculosis . Here, we show that modifications to the acylaminooxadiazole scaffold can improve potency and tune mycobacterial species specificity, resulting in molecules that kill M. avium , M. abscessus , and M. tuberculosis clinical isolates. Free iron was previously shown to antagonize antibacterial activity and decrease the inhibition of trans -translation by acylaminooxadiazoles, but we found that biologically relevant iron sources such as hemin and transferrin do not affect activity. Mutants depleted for tmRNA and mutants defective in siderophore-mediated iron utilization are both hypersusceptible to acylaminooxadiazole-based trans- translation inhibitors, indicating a dual mechanism of action involving both direct inhibition of trans- translation and metal starvation. These findings establish acylaminooxadiazoles as dual-mechanism antimycobacterial agents that couple inhibition of trans -translation with disruption of iron homeostasis.