Journal
JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY
Volume 75, Issue 9, Pages 2564-2572Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jac/dkaa200
Keywords
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Funding
- Pasteur Institute-Cenci Bolognetti Foundation
- Italian Cystic Fibrosis Research Foundation [15/2019]
- Italian Ministry of Education, University and Research (MIUR) PRIN 2017 [2012WJSX8K]
- Sapienza University of Rome [RM11916B885E57B66]
- Excellence Departments grant from MIUR
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Background: Colistin is a last-resort treatment option for many MDR Gram-negative bacteria. The covalent addition of L-aminoarabinose to the lipid A moiety of LPS is the main colistin resistance mechanism in the human pathogen Pseudomonas aeruginosa. Objectives: Identification (by in silico screening of a chemical library) of potential inhibitors of ArnT, which catalyses the last committed step of lipid A aminoarabinosylation, and their validation in vitro as colistin adjuvants. Methods: The available ArnT crystal structure was used for a docking-based virtual screening of an in-house library of natural products. The resulting putative ArnT inhibitors were tested in growth inhibition assays using a reference colistin-resistant P. aeruginosa strain. The most promising compound was further characterized for its range of activity, specificity and cytotoxicity. Additionally, the effect of the compound on lipid A aminoarabinosylation was verified by MS analyses of lipid A. Results: A putative ArnT inhibitor (BBN149) was discovered by molecular docking and demonstrated to specifically potentiate colistin activity in colistin-resistant P. aeruginosa isolates, without relevant effect on colistinsusceptible strains. BBN149 also showed adjuvant activity against colistin-resistant Klebsiella pneumoniae and low toxicity to bronchial epithelial cells. Lipid A aminoarabinosylation was reduced in BBN149-treated cells, although only partially. Conclusions: This study demonstrates that in silico screening targeting ArnT can successfully identify inhibitors of colistin resistance and provides a promising lead compound for the development of colistin adjuvants for the treatment of MDR bacterial infections.
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