The antibacterial activity and mechanisms of Trp-containing peptides against multidrug-resistant Pseudomonas aeruginosa persisters

Bacterial persisters avoid antibiotic-mediated death by entering a dormant state and are considered a major cause of antibiotic treatment failure. Antimicrobial peptides (AMPs) with membrane-disrupting activity are promising drugs to eradicate persister cells. In this study, carbonyl cyanide m-chlorophenylhydrazone (CCCP), ciprofloxacin (CIP), and rifampicin (RFP) were applied to induce the formation of multidrug-resistant Pseudomonas aeruginosa (MRPA0108) persisters, and the antibacterial activity and mechanisms of I1W and L12W (two Trp-containing peptides designed in our lab) against MRPA0108 persisters were investigated. The results showed that I1W and L12W displayed potent antibacterial activity against MRPA0108 persisters. Both Trp-containing peptides disturbed the inner and outer membrane of MRPA0108 persisters. In addition, I1W and L12W revealed novel antibacterial mechanisms by decreasing the enzymatic activities of superoxide dismutase (SOD) and catalase (CAT), increasing reactive oxygen species (ROS) and malondialdehyde (MDA) levels, consequently leading to oxidative stress. The transcriptome profile of I1W-treated MRPA0108 persisters revealed that the genes involved in carbon metabolism, biosynthesis of amino acids, and the TCA cycle were downregulated, indicating that I1W interfered with metabolism and energy synthesis processes. Furthermore, both Trp-containing peptides displayed synergistic activities with antibiotic tobramycin and showed additive activities with cefepime or ciprofloxacin, which revealed a potential therapeutic strategy for the eradication of MRPA0108 persisters.