title: Development of colistin resistance in pmrA-, phoP-, parR- and cprR-inactivated mutants of Pseudomonas aeruginosa.
abstract: OBJECTIVE
  Colistin susceptibility in Pseudomonas aeruginosa is associated with a lipopolysaccharide (LPS) structure that is controlled by the modulation of several two-component regulatory systems. In this study, we attempted to elucidate the role of these two-component systems in the development of colistin resistance in P. aeruginosa.
  
  
  METHODS
  pmrA-, phoP-, parR- or cprR-inactivated mutants were constructed from a colistin-susceptible P5 strain. Colistin-resistant mutants (P5R, P5ΔpmrA-R, P5ΔphoP-R, P5ΔparR-R and P5ΔcprR-R) were developed in vitro from a wild-type strain (P5) and pmrA-, phoP-, parR- or cprR-inactivated mutants by serial passage in colistin-containing media. Expression levels of the pmrA, phoP, parR, cprR and arnB genes were determined and amino acid alterations of two-component regulatory systems during development of colistin resistance were also investigated.
  
  
  RESULTS
  While P5ΔpmrA-R, P5ΔparR-R and P5ΔcprR-R showed elevated expression of the phoP gene, the expression levels of the pmrA, parR and cprR genes were not different between gene-inactivated mutants and the adapted colistin-resistant mutants. P5ΔphoP-R showed no significant elevation in expression of any of the pmrA, parR or cprR genes. The arnB gene was overexpressed in all in vitro-selected colistin-resistant mutants compared with colistin-susceptible wild-type and gene-inactivated mutants. Three amino acid alterations in PhoQ and three in ParS were identified in induced colistin-resistant mutants.
  
  
  CONCLUSIONS
  Our data suggest that individual two-component systems may not be essential for the acquisition of colistin resistance in P. aeruginosa. The PhoPQ two-component system may play a major role in the development of colistin resistance in our strains, but alternative or compensatory pathways may exist.
authors.affiliation: Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea.
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea.
authors.forename: Eun Seon
authors.initials: ES
authors.lastname: Chung
authors.affiliation: Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea.
authors.forename: In Young
authors.initials: IY
authors.lastname: Na
authors.affiliation: Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea.
authors.forename: Hyunkeun
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea.
authors.forename: Dongwoo
authors.initials: D
authors.lastname: Shin
authors.affiliation: Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea ksko@skku.edu.
authors.forename: Kwan Soo
authors.initials: KS
authors.lastname: Ko
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D003091:Colistin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D009154:Mutation / Q000235:genetics*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C086169:ParR protein, bacteria; D012097:Repressor Proteins; C081902:pmrA protein, Bacteria; C061064:PhoP protein, Bacteria; D003091:Colistin
keywords: arnB; qRT–PCR; two-component regulatory systems