Amphiphilic nebramine analogs synergize with β-lactam/β-lactamase inhibitor combinations, including cefepime–taniborbactam and meropenem–xeruborbactam against metallo-β-lactamase-carrying <i>Pseudomonas aeruginosa</i>

Cefepime-taniborbactam (FEP-TAN) and meropenem-xeruborbactam (MEM-XER) are β-lactam-β-lactamase inhibitor (BL-BLI) combinations currently in development and both projected to treat metallo-β-lactamase (MBL)-producing Gram-negative pathogens. Among Gram-negative pathogens, the low permeability of the outer membrane of <i>Pseudomonas aeruginosa</i> poses unique challenges to drug discovery in general and to BL-BLIs in particular. This study set out to augment β-lactam antibiotic potency by enhancing outer membrane permeability of <i>P. aeruginosa</i> using novel amphiphilic aminoglycoside-based outer membrane permeabilizers. Amphiphilic nebramines acting as outer membrane permeabilizers, were synthesized and evaluated in combination with β-lactam antibiotics and BL-BLIs against <i>P. aeruginosa</i> clinical isolates harbouring a number of resistance determinants, including MBLs. Dually guanidinylated and C-5-alkylated analogs of nebramine were able to sensitize MBL-carrying <i>P. aeruginosa</i> to various BL-BLIs. The amphiphilic nebramine derivative, compound 4, synergized with multiple β-lactam antibiotics and BL-BLIs including aztreonam-avibactam (ATM-AVI), FEP-TAN and MEM-XER against multidrug-resistant <i>P. aeruginosa</i> isolates. In particular, compound 4 + ATM-AVI, restored susceptibility to all nine β-lactamase (including MBL)-harbouring <i>P. aeruginosa</i> strains that were previously resistant to aztreonam. Compound 4 was found to be less toxic than both polymyxin B and its corresponding amphiphilic tobramycin counterpart (compound 7) in human renal cell lines, RPTEC and HK-2. Overall, our study suggests that addition of compound 4 alongside next-generation BL-BLIs such as FEP-TAN, MEM-XER as well as the recently approved ATM-AVI combination can overcome intrinsic and acquired <i>in vitro P. aeruginosa</i> resistance determinants that confer high-level resistance to β-lactam antibiotics.