Mutations in genes lpxL1 , bamA , and pmrB impair the susceptibility of cystic fibrosis strains of Pseudomonas aeruginosa to murepavadin

Murepavadin is a peptidomimetic exhibiting specific inhibitory activity against species. In the present study, its activity was assessed on 230 cystic fibrosis (CF) strains of isolated from 12 French hospitals, in comparison with 12 other antipseudomonal antibiotics. Although murepavadin is still in preclinical stage of development, 9.1% ( = 21) of strains had a minimum inhibitory concentration (MIC) >4 mg/L, a level at least 128-fold higher than the modal MIC value of the whole collection (≤0.06 mg/L). Whole-genome sequencing of these 21 strains along with more susceptible isogenic counterparts coexisting in the same patients revealed diverse mutations in genes involved in the synthesis ( and ) or transport of lipopolysaccharides ( , , and ), or encoding histidine kinases of two-component systems ( and ). Allelic replacement experiments with wild-type reference strain PAO1 confirmed that alteration of genes , and/or can decrease the murepavadin susceptibility from 8- to 32-fold. Furthermore, we found that specific amino acid substitutions in histidine kinase PmrB (G188D, Q105P, and D45E) reduce the susceptibility of to murepavadin, colistin, and tobramycin, three antibiotics used or intended to be used (murepavadin) in aerosols to treat colonized CF patients. Whether colistin or tobramycin may select mutants resistant to murepavadin or the opposite needs to be addressed by clinical studies.