Chemical Synthetic Lethality Screens Identify Selective Drug Combinations against <i>Pseudomonas aeruginosa</i>

The emergence of bacterial ESKAPE pathogens presents a formidable challenge to global health, necessitating the development of innovative strategies for antibiotic discovery. Here, we leverage chemical synthetic lethality to locate therapeutic combinations of small molecules against multidrug-resistant <i>Pseudomonas aeruginosa</i>. Using a transposon screen, we identify PyrD as a target for sensitizing <i>P. aeruginosa</i> to subinhibitory doses of ceftazidime. High-throughput inhibitor screens identify two PyrD inhibitors, nordihydroguaiaretic acid (NDGA) and chlorhexidine (CHX), each of which does not significantly affect growth in isolation but exhibits chemical synthetic lethality when combined with low-dose ceftazidime. Downstream biochemical studies elucidate the mechanism of inhibition by NDGA and CHX. Remarkably, this combination is toxic to <i>P. aeruginosa</i> but leaves commensal bacteria, which are more susceptible to antibiotics, unscathed. Aside from advancing drug combinations that may be explored further in the future, our results offer a new approach for devising potent and specific drug combinations against recalcitrant pathogens.