Lon dysfunction-mediated collateral sensitivity drives effective antibiotic combination therapies against tigecycline-resistant pathogens.

Tigecycline is a last-resort antibiotic primarily used to treat severe infections caused by multidrug-resistant (MDR) bacteria. However, the emergence of constantly appearing resistance determinants has drastically compromised its clinical effectiveness. Rational antibiotic combination provides a productive approach to tackle MDR pathogens. Herein, we show that evolved tigecycline-resistant Escherichia coli and Salmonella Enteritidis exhibit collateral sensitivity to aminoglycosides and nitrofurantoin. Proton motive force alterations mediate tigecycline resistance, simultaneously enhancing bacterial susceptibility to aminoglycosides. Notably, Lon dysfunction in tigecycline-resistant strains causes overexpression of sulA, increased lipopolysaccharide biosynthesis, and disrupted membrane homeostasis, leading to bacterial death upon nitrofurantoin exposure. The combination of tigecycline and nitrofurantoin effectively eradicates both evolved tigecycline-resistant bacteria and those carrying the tet(X4) gene while also hindering the development of tigecycline resistance. Together, our study suggests that combining tigecycline with existing antibiotics, rationally designed by harnessing collateral sensitivity, represents a promising therapeutic paradigm to combat tigecycline-resistant pathogens.