Aminoarabinosylation of Lipid A Is Critical for the Development of Colistin Resistance in Pseudomonas aeruginosa

Abstract

Lipid A aminoarabinosylation is invariably associated with colistin resistance in Pseudomonas aeruginosa; however, the existence of alternative aminoarabinosylation-independent colistin resistance mechanisms in this bacterium has remained elusive. By combining reverse genetics with experimental evolution assays, we demonstrate that a functional lipid A aminoarabinosylation pathway is critical for the acquisition of colistin resistance in reference and clinical P. aeruginosa isolates. This highlights lipid A aminoarabinosylation as a promising target for the design of colistin adjuvants against P. aeruginosa.

Keywords: Pseudomonas aeruginosa; acquired resistance; colistin.

FIG 1

Maximum colistin resistance acquired by reference (PAO1 and PA14) or cystic fibrosis P. aeruginosa isolates (KK1, KK27, and TR1) and/or their corresponding ΔarnBCA mutants after sequential passages in Mueller-Hinton broth in the presence of increasing colistin concentrations (0.25 to 16 μg/ml) in a short-term experiment (single passage at each colistin concentration) (A) or a long-term experiment (5 serial passages at each colistin concentration) (B) (see supplemental material for experimental details). Fifteen independent cultures were analyzed for each strain in each experiment. Cultures showing no visible growth after 5 days were considered extinct.