In Vivo Emergence of Colistin Resistance in Acinetobacter Baumannii Clinical Isolates of Sequence Type 357 During Colistin Treatment

Diagn Microbiol Infect Dis. 2014 Jul;79(3):362-6. doi: 10.1016/j.diagmicrobio.2014.03.027. Epub 2014 Apr 12.


This study was performed to investigate the mechanisms of in vivo acquisition of colistin resistance in A. baumannii during colistin treatment. Three colistin-susceptible/resistant pairs of A. baumannii were recovered from patients who underwent colistin treatment. All of the 6 isolates included in this study shared an identical sequence type (ST), ST375, and they showed identical SmaI-macrorestriction patterns by pulsed-field gel electrophoresis. The individual colistin-resistant isolates harbored distinct mutations in the pmrB gene. Mutations detected in the pmrB gene were Ala227Val, Pro233Ser, and frame shift from Phe26. In matrix-assisted laser desorption ionization-time of flight analysis, colistin-resistant isolates were different from their colistin-susceptible counterparts, and they showed additional distinct peaks at 1852 m/z, 1937 m/z, 1954 m/z, 1975 m/z, 2034 m/z, and 2157 m/z. In vivo selection of colistin-resistant A. baumannii occurred independently in strains of ST357 during colistin treatment, and the strains acquired colistin resistance via mutations in the pmrB gene resulting in modification of lipid A components.

Keywords: Lipid A; Lipopolysaccharide; Phosphoethanolamine; PmrB gene; Polymyxins.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter Infections / drug therapy*
  • Acinetobacter Infections / microbiology*
  • Acinetobacter baumannii / classification
  • Acinetobacter baumannii / drug effects*
  • Acinetobacter baumannii / genetics
  • Acinetobacter baumannii / isolation & purification*
  • Aged
  • Anti-Bacterial Agents / therapeutic use*
  • Bacterial Proteins / genetics
  • Colistin / therapeutic use*
  • Drug Resistance, Bacterial*
  • Electrophoresis, Gel, Pulsed-Field
  • Female
  • Genotype
  • Humans
  • Male
  • Middle Aged
  • Molecular Typing
  • Mutation
  • Polymorphism, Restriction Fragment Length
  • Selection, Genetic
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Transcription Factors / genetics


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • PmrB protein, bacteria
  • Transcription Factors
  • Colistin