Korean J Clin Microbiol.  2010 Mar;13(1):27-33. 10.5145/KJCM.2010.13.1.27.

Carbapenem Resistance Mechanisms and Molecular Epidemiology of Acinetobacter spp. from Four Hospitals in Seoul and Gyeonggi Province in 2006

• Roh KH
• Kim CK
• Yum JH
• Yong D
• Jeong SH
• Lim CS
• Lee CK
• Cho Y
• Lee K
• Chong Y

• KMID: 1828592
• DOI: http://doi.org/10.5145/KJCM.2010.13.1.27

Abstract

BACKGROUND
Increasing numbers of Acinetobacter spp. resistant to multiple drugs, including carbapenem, has been a serious problem. The aims of this study were to determine carbapenem resistance patterns and mechanisms, as well as to study the molecular epidemiology of Acinetobacter spp.
METHODS
Clinical isolates of Acinetobacter spp. were collected from May to November in 2006. Antimicrobial susceptibility testing was performed using CLSI disk diffusion and agar dilution methods. Metallo-beta-lactamase- and OXA carbapenemase-producing isolates were detected by PCR. Carbapenem resistance and hydrolytic activities were compared according to OXA type and presence of ISAba1. Pulsed-field gel electrophoresis (PFGE) was performed to determine the epidemiologic features.
RESULTS
The imipenem non-susceptible rates were variable from 10% to 67%. Among 151 isolates carrying bla(OXA-51-like), 75 isolates carried both bla(OXA-51-like) and ISAba1, and 25 isolates had both bla(OXA-51-like), bla(OXA-23-like), and ISAba1. Carbapenem MICs of both bla(OXA-51-like) and ISAba1-carrying isolates were higher than those with bla(OXA-51-like) only. Carbapenem MICs of bla(OXA-23-like)-carrying isolates were higher than those with both bla(OXA-51-like) and ISAba1. Both bla(OXA-51-like) and ISAba1-carrying isolates and blaOXA-51-like, blaOXA-23-like, and ISAba1-carrying isolates demonstrated higher hydrolysis activities in oxacillin and carbapenems. Most of the tested isolates were susceptible to tigecycline, and all of them were susceptible to colistin. Pulsed-field gel electrophoresis suggested that there had been several outbreaks of bla(OXA-23-like) and bla(OXA-51-like)-positive strains.
CONCLUSION
Carbapenem non-susceptible Acinetobacter isolates and OXA carbapenemase-producing isolates were prevalent. Dissemination of bla(OXA)-harboring isolates may make it difficult to treat infections due to carbapenem-resistant Acinetobacter spp. Further surveillance studies are required to prevent the spread of carbapenem resistance.

Keyword

OXA carbapenemase; Carbapenem; Acinetobacter; Outbreak

MeSH Terms

Acinetobacter
Agar
Carbapenems
Colistin
Diffusion
Disease Outbreaks
Electrophoresis, Gel, Pulsed-Field
Hydrolysis
Imipenem
Lifting
Minocycline
Molecular Epidemiology
Oxacillin
Oxytocin
Polymerase Chain Reaction
Agar
Carbapenems
Colistin
Imipenem
Minocycline
Oxacillin
Oxytocin

Figure

• 

  Fig. 1. Pulsed-field gel electrophoresis (PFGE) patterns of SmaI-restricted genomic DNA of Acinetobacter spp. isolates. (A) Isolates having blaOXA-51 and ISAbaI. Lane I to IX, different clones from 4 hospitals; and (B) isolates having both blaOXA-51, blaOXA-23 and ISAbaI. Lane I-1 to IV, different clones from 4 hospitals; Molecular size (ladder marker) is given in kilobases.

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