Antibiotic Potentiation in Multidrug-Resistant Gram-Negative Pathogenic Bacteria by a Synthetic Peptidomimetic

Abstract

The peptidomimetic H-[NLys-t BuAla] 6 -NH 2 (CEP-136), which exhibits low inherent antimicrobial activity against Gramnegative bacteria (MIC = 16−64 μM), was shown to significantly potentiate the antibacterial activity of several clinically important antibiotics against the human pathogens Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. Thus, the antibacterial spectrum of rifampicin, clarithromycin, and azithromycin could be extended to include also these Gram-negative bacteria. Additionally, the potentiation effect was demonstrated in a panel of clinically relevant multidrug-resistant isolates including extendedspectrum β-lactamase (ESBL)-and carbapenemase-producing as well as colistin-resistant strains. For some peptidomimetic−antibiotic combinations, the strong synergy corresponded to a more than 50fold reduction of the minimal inhibitory concentration of the antibiotic. Mechanistic studies indicate that the potentiation arises from a permeabilization effect exerted on the outer membrane lipopolysaccharide layer of the Gram-negative bacteria without significant disruption of the inner membrane. Furthermore, the peptidomimetic enhancer exhibited only a marginal effect on the viability of mammalian HepG2 cells even at concentrations 100fold higher than that enabling the antibiotic enhancement. Also, a low hemolytic activity combined with limited in vivo acute toxicity of CEP-136 in healthy mice allowed in vivo validation of the potentiation effect on both rifampicin and azithromycin treatment in a murine peritonitis model. Thus, CEP-136 is an interesting hit compound for further development of effective adjuvants for repurposing antibiotics for use against infections by multidrug-resistant Gram-negative bacteria.

The Use of Antibody-Antibiotic Conjugates to Fight Bacterial Infections

“…The use of antibiotics has significantly improved the treatment of bacterial infections. However, the increase of resistant pathogens has leveraged the study of innovative strategies ( Mood et al, 2021 ). As a result, the use of peptides emerged as a promising alternative ( Rima et al, 2021 ).…”

Anionic Self‐Assembling Supramolecular Enhancers of Antimicrobial Efficacy against Gram‐Negative Bacteria

“…In a similar strategy to that employed by the antimicrobial potentiators reported by Nielsen et al, we seek to use the membrane destabilization effects of the SSAs to enhance the efficacy of antimicrobial treatment. [18] Gram-negative P. aeruginosa represents the "P" in the ESKAPE pathogens, a group of potentially drug-resistant bacteria that have been listed as urgently requiring novel antimicrobials. [16a,25] Indeed, carbapenem-resistant P. aeruginosa has been placed in the highest priority list of bacteria requiring new treatments, as published by the World Health Organization (2017).…”

“…In a similar strategy to that employed by the antimicrobial potentiators reported by Nielsen et al, we seek to use the membrane destabilization effects of the SSAs to enhance the efficacy of antimicrobial treatment. [ 18 ]…”

“…Nielsen and co‐workers built upon these data, showing that the peptide mimic H‐[NLys‐ t BuAla] 6 ‐NH 2 was capable of permeabilizing the membranes of a range of pathogenic bacteria including E. coli, Klebsiella pneumoniae , Acinetobacter baumannii , and Pseudomonas aeruginosa ( P. aeruginosa ). [ 18 ] Here, the authors showed that outer membrane permeabilization was concurrent with antimicrobial efficacy enhancement, observing an increase in the activity of three antibiotics, rifampicin, clarithromycin, and azithromycin against these bacteria. Beyond antimicrobial peptides, the small molecule antifungal drug pentamidine was investigated by Stokes et al.…”

Dioctanoyl Ultrashort Tetrabasic β-Peptides Sensitize Multidrug-Resistant Gram-Negative Bacteria to Novobiocin and Rifampicin

“…Peptidomimetic approaches can mitigate proteolytic susceptibility by removing the peptide-like character of AMPs thereby resulting in the inability of proteases to recognize and degrade the resulting mimic molecule ( Domalaon et al, 2016 ). Several peptidomimetic strategies can be enacted in lead AMP candidates including isosteric replacement of the peptide backbone, replacing naturally occurring L -amino acids with D -amino acids, and the use of β-amino acids and peptoid building blocks ( Rink et al, 2010 ; Molchanova et al, 2017 ; Baker et al, 2019 ; Mood et al, 2021 ). For instance, dilipid ultrashort tetrabasic peptidomimetics (dUSTBPs) were previously developed from dUSCL lead candidates by introducing the branched molecular scaffold, N , N -bis(3-aminopropyl)glycine ( N bap), into the structure to interrupt the peptide backbone ( Ramirez et al, 2020 ).…”