Mutations in geneslpxL1, bamAandpmrBimpair the susceptibility of cystic fibrosis strains ofPseudomonas aeruginosato murepavadin

Abstract

AbstractMurepavadin is a peptidomimetic exhibiting specific inhibitory activity againstPseudomonasspecies. In the present study, itsin vitroactivity was assessed on 230 cystic fibrosis (CF) strains ofP. aeruginosaisolated from twelve French hospitals, in comparison with twelve other antipseudomonal antibiotics. Although murepavadin is still in pre-clinical stage of development, 9.1% (n=21) of the strains displayed a resistance superior to 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 (lpxL1andlpxL2) or transport of lipopolysaccharides (bamA, lptD, andmsbA), or encoding histidine kinases of two-component systems (pmrBandcbrA). Allelic replacement experiments with wild-type reference strain PAO1 confirmed that alteration of geneslpxL1, bamAand/orpmrBcan increase murepavadin resistance from 8- to 32-fold. Furthermore, we found that specific amino-acid substitutions in histidine kinase PmrB (G188D, Q105P, and D45E) reduce the susceptibility ofP. aeruginosato 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.