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Dilipid ultrashort cationic lipopeptides as adjuvants for chloramphenicol and other conventional antibiotics against Gram-negative bacteria

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Abstract

The necessity to develop therapeutic agents and strategies to abate the spread of antibiotic-resistant pathogens is prominent. Antimicrobial peptides (AMPs) provide scaffolds and inspiration for antibiotic development. As an AMP of shorter scaffold, eight dilipid ultrashort cationic lipopeptides (dUSCLs) were prepared consisting of only four amino acids and varying dilipids. Lipids were acylated at the peptide N-terminus and the ε-amine side chain of the N-terminal l-lysine. Compounds that possess aliphatic dilipids of ≥ 11 carbons-long showed significant hemolysis and therefore limited therapeutic application. Several non-hemolytic dUSCLs were identified to enhance the activity of chloramphenicol and other conventional antibiotics against Gram-negative bacteria. Compounds 2 and 6 have a short peptide sequence of KKKK and KKGK, respectively, and are both acylated with an aliphatic dilipid of nine carbons-long potentiated chloramphenicol against MDR clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae. Both dUSCLs showed comparable adjuvant potency in combination with chloramphenicol. However, dUSCL 2 synergized with a wider span of antibiotic classes against P. aeruginosa relative to dUSCL 6 that included rifampicin, trimethoprim, minocycline, fosfomycin, piperacillin, ciprofloxacin, levofloxacin, moxifloxacin, linezolid and vancomycin. Our data revealed that dUSCLs can indirectly disrupt active efflux of chloramphenicol in P. aeruginosa. This along with their membrane-permeabilizing properties may explain the dUSCLs synergistic combination with conventional antibiotics against Gram-negative bacteria.

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Acknowledgements

This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Manitoba Health Research Council (MHRC). We thank Dr. A. Kumar (University of Manitoba) for generously providing the efflux-deficient P. aeruginosa PAO200 and PAO750 strains. We thank Dr. Richard Hodges (University of Manitoba) for generously providing fresh red blood cells from pigs in their Animal Care and Veterinary Services facility.

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Correspondence to Frank Schweizer.

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All procedures performed in studies involving animals were in accordance with the ethical standards of the University of Manitoba which the studies were conducted.

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Informed consent was obtained from all the individual participants included in the study.

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Handling Editor: J. Metcalf.

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Domalaon, R., Brizuela, M., Eisner, B. et al. Dilipid ultrashort cationic lipopeptides as adjuvants for chloramphenicol and other conventional antibiotics against Gram-negative bacteria. Amino Acids 51, 383–393 (2019). https://doi.org/10.1007/s00726-018-2673-9

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  • DOI: https://doi.org/10.1007/s00726-018-2673-9

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