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

In vivo emergence of colistin resistance in Acinetobacter baumannii clinical isolates of sequence type 357 during colistin treatment.

Author information

1
Samkwang Medical Laboratories, Seoul, Republic of Korea.
2
Department of Dental Hygiene, Silla University, Busan, Republic of Korea.
3
Department of Laboratory Medicine, Kwandong University College of Medicine, Gangneung, Republic of Korea.
4
Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Republic of Korea. Electronic address: kscpjsh@yuhs.ac.
5
Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Republic of Korea.

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.

KEYWORDS:

Lipid A; Lipopolysaccharide; Phosphoethanolamine; PmrB gene; Polymyxins

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