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 Pseudomonas species. In the present study, its in vitro activity was assessed on 230 cystic fibrosis (CF) strains of Pseudomonas aeruginosa isolated from 12 French hospitals, in comparison with 12 other antipseudomonal antibiotics. Although murepavadin is still in preclinical stage of development, 9.1% (n = 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 (lpxL1 and lpxL2) or transport of lipopolysaccharides (bamA, lptD, and msbA), or encoding histidine kinases of two-component systems (pmrB and cbrA). Allelic replacement experiments with wild-type reference strain PAO1 confirmed that alteration of genes lpxL1, bamA, and/or pmrB 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 P. aeruginosa 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.

[Induction of labor in twin pregnancies compared to singleton pregnancies; risk factors for failure]

OBJECTIVES

The aim of this study was to evaluate the modalities of induction of labour in twin pregnancies compared with singleton pregnancies and to identify risk factors for failure.

MATERIALS ET METHODS

A retrospective population-based study was conducted at the Toulouse University Hospital to compare a cohort of diamniotic twin gestations (Twin A in vertex presentation), with induction of labour ≥36 weeks of gestation, between January 2007 and December 2012, to a singleton's cohort that were induced ≥36 weeks of gestation during the 2007 year. One singleton pregnancy was matched for each twin pregnancy with parity and gestational age.

RESULTS

One hundred and fifty-six twins pregnancies met the inclusion criteria for an induction of labor and were compared to 156 single pregnancies. The same and standard protocol of induction of labor was used for the two cohorts (intrauterine balloon catheter±dinoprostone/ocytocine). The cesarean section rate for failed labor induction (cesarean in latent phase) was similar in the 2 populations (14.7% for twin vs 13.5% for single; P=0.66). The factors associated to failed induction of labor in the total population were nulliparity (OR=1.49) and Bishop score<6 at the beginning of the induction (OR=2.83).

CONCLUSION

Twin did not appear as risk of failed induction. The protocol for induction of labor in singletons may be safely proposed to twin gestations.