Multi-omics reveals the synergistic mechanism of polymyxin B and diethyldithiocarbamate against Pseudomonas aeruginosa.

Abstract

Resistance to polymyxin B (PMB) in carbapenem-resistant Pseudomonas aeruginosa (CRPA) has become a global issue. A promising approach to rescue PMB treatment failures is to repurpose non-antibiotics as adjuvants to enhance the efficacy of antibiotics against CRPA. Here, we identified that the combination of PMB and diethyldithiocarbamate (DDC) had a high synergistic effect against PMB-resistant Pseudomonas aeruginosa (P. aeruginosa) strains in vitro and significantly hindered the biofilm formation. The PMB/DDC combination was effective in treating PMB-resistant P. aeruginosa infection model in vivo, as evidenced by higher survival rates in five days and lower bacterial loads in lung tissue and liver. Comprehensive multi-omics analysis revealed that the resistance of P. aeruginosa P2550 to PMB was determined by chromosomally encoded rather than plasmid-mediated mobilized colistin resistance (MCR) clusters. The combination down-regulated the expression of the operons arnBCADTEF at 2 h, which regulate LPS modification, and the abundance of metabolites of amino sugars and nucleotide sugars related to Lipid A biosynthesis and Lipid A modification were significantly perturbed. The Gac/Rsm pathway, quorum sensing (QS) system, cAMP/Vfr signaling, and c-di-GMP signaling, which are pathways associated with biofilm formation, were significantly inhibited within the first 4 h. In addition, the PMB/DDC combination significantly disturbed metabolic pathways, including arginine biosynthesis, the tricarboxylic acid cycle (TCA), and nucleotide metabolism. Notably, PMB alone, DDC alone, and the combination disrupted membrane-associated glycerophospholipid metabolism. The study highlights the potential of the PMB/DDC combination for treating PMB-resistant P. aeruginosa infections and elucidates the synergistic bactericidal mechanism of the combination through multi-omics methods.