title: A peptide based on homologous sequences of the β-barrel assembly machinery component BamD potentiates antibiotic susceptibility of Pseudomonas aeruginosa.
abstract: OBJECTIVE
  The β-barrel assembly machinery (BAM) complex plays a critical role in outer membrane protein (OMP) biogenesis. The outer membrane (OM) of Pseudomonas aeruginosa is centrally involved in mechanisms of antibiotic resistance. This study aimed to identify effects of a synthetic peptide based on conserved sequences in the putative BamA-binding region of BamD, focusing on antibiotic susceptibility and OMP characteristics in P. aeruginosa.
  
  
  METHODS
  We synthesized a peptide FIRL (Phe-Ile-Arg-Leu-CONH(2)) with a sequence related to that of the BamD protein. We assessed antibiotic susceptibility of P. aeruginosa PAO1 using the chequerboard method and a time-kill assay. Changes in OMPs and in OM permeability were examined using SDS-PAGE, western blot analysis and nitrocefin assays. The combined effects of the peptide and antibiotics were investigated using a mouse pneumonia model.
  
  
  RESULTS
  Although the peptide alone exerted no antimicrobial effect, it reduced the MICs of colistin, levofloxacin, erythromycin, vancomycin and rifampicin for P. aeruginosa PAO1 by 4-fold or more. Time-kill tests revealed bacterial numbers were significantly reduced after 2 h of incubation with the peptide plus colistin or levofloxacin. Moreover, in the presence of the peptide, expression of OprM was reduced by a third, and OM permeability was increased. The combination of the peptide (2.08 mg/kg) and colistin (1.25 mg/kg) significantly reduced P. aeruginosa by more than 1 log cfu/mL in a mouse pneumonia model.
  
  
  CONCLUSIONS
  We show, for the first time, that a synthetic peptide based on homologous sequences of BamD can potentiate antibiotic susceptibility of P. aeruginosa.
authors.affiliation: Department of Microbiology and Infectious Diseases,  Toho University Faculty of Medicine, Tokyo,  Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Mori
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ishii
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tateda
authors.forename: Soichiro
authors.initials: S
authors.lastname: Kimura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kouyama
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Inoko
authors.forename: Shigeki
authors.initials: S
authors.lastname: Mitsunaga
authors.forename: Keizo
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Eisaku
authors.initials: E
authors.lastname: Yoshihara
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D058491:Bacterial Load; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D003091:Colistin / Q000008:administration & dosage; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D064704:Levofloxacin; D008168:Lung / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000008:administration & dosage; D010455:Peptides / Q000008:administration & dosage / Q000235:genetics / Q000494:pharmacology*; D018410:Pneumonia, Bacterial / Q000188:drug therapy; D011485:Protein Binding; D011552:Pseudomonas Infections / Q000188:drug therapy; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D010455:Peptides; D064704:Levofloxacin; D015242:Ofloxacin; D003091:Colistin