Nitroxoline Shows Synergy with Colistin Potentiating its Bactericidal Efficacy in Opportunist Pathogen Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa is a highly virulent Gram-negative pathogen that exhibits multiple mechanisms of antibiotic resistance, including resistance to colistin, a last-resort therapeutic agent, posing a significant clinical challenge. Recently designated by the World Health Organization (WHO) as a high-priority pathogen, P. aeruginosa underscores the urgent need for novel therapeutic strategies. In this study, we explored the potential of combination therapy, specifically investigating the synergistic interaction between colistin and nitroxoline, a hydroxyquinoline derivative, against a highly colistin-resistant P. aeruginosa strain.Bacterial viability was assessed through growth curve analysis, and the mechanistic basis of the observed synergy was examined using membrane permeability assays, intracellular reactive oxygen species (ROS) quantification, and gene expression profiling via quantitative real-time PCR (qRT-PCR). Additionally, the impact of this combination on bacterial survival was evaluated by analyzing its effects on biofilm formation and persister cell development under antimicrobial stress, both critical contributors to chronic and treatment-refractory infections in humans.Our results demonstrate that nitroxoline potentiates the bactericidal activity of colistin by enhancing membrane permeability, leading to significant inhibition of planktonic growth and pronounced efficacy against structured microbial communities such as biofilms and persister cells. Furthermore, the combination therapy completely suppressed bacterial motility, a critical virulence trait that facilitates immune evasion.These findings present a compelling therapeutic strategy to combat antibiotic resistance in Gram-negative pathogens, including both wild-type and drug-resistant clinical isolates of P. aeruginosa and Acinetobacter baumannii. The study highlights the significant potential of the colistin-nitroxoline combination to mitigate colistin resistance and reduce the global burden of multidrug-resistant infections.