title: In vivo emergence of colistin resistance in Acinetobacter baumannii clinical isolates of sequence type 357 during colistin treatment.
abstract: 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.
authors.affiliation: Samkwang Medical Laboratories, Seoul, Republic of Korea.
authors.forename: Yoonjung
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Dental Hygiene, Silla University, Busan, Republic of Korea.
authors.forename: Il Kwon
authors.initials: IK
authors.lastname: Bae
authors.affiliation: Department of Laboratory Medicine, Kwandong University College of Medicine, Gangneung, Republic of Korea.
authors.forename: Hyukmin
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Republic of Korea. Electronic address: kscpjsh@yuhs.ac.
authors.forename: Seok Hoon
authors.initials: SH
authors.lastname: Jeong
authors.affiliation: Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Dongeun
authors.initials: D
authors.lastname: Yong
authors.affiliation: Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy* / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001426:Bacterial Proteins / Q000235:genetics; D003091:Colistin / Q000627:therapeutic use*; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D058889:Molecular Typing; D009154:Mutation; D012150:Polymorphism, Restriction Fragment Length; D012641:Selection, Genetic; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014157:Transcription Factors / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C409039:PmrB protein, bacteria; D014157:Transcription Factors; D003091:Colistin
keywords: Lipid A; Lipopolysaccharide; Phosphoethanolamine; PmrB gene; Polymyxins