Korean J Clin Microbiol.  2005 Oct;8(2):121-129.

Molecular Epidemiology of Infection Caused by OXA-23 or IMP-1 beta-Lactamase-Producing Acinetobacter baumannii

• Park KO
• Son HC
• Bae IK
• Jeong SH

Abstract

BACKGROUND
The purposes of this study were to investigate the prevalence of imipenem-resistant clinical Acinetobacter baumannii isolates and to determine the mechanism of the resistance.
METHODS
During the period of June to September 2004, susceptibility to imipenem of A. baumannii isolates from a hospital in Busan, Korea were investigated. The isolates were screened for the production of carbapenemase and metallo-beta-lactamase by Modified-Hodge and EDTA-disk synergy tests, respectively; minimum inhibitory concentrations (MICs) were determined by agar dilution method. Genes coding for GES, IMP, VIM, SMP-1, GIM-1 and OXA type beta-lactamases were searched by PCR amplification, and the PCR products were subjected to direct sequencing. Isoelectric points of beta-lactamases were estimated by isoelectric focusing and the epidemiological relationships of isolates were investigated by enterobacterial repetitive intergenic consensus (ERIC) PCR.
RESULTS
Fifty eight strains of A. baumannii were isolated from clinical specimens during the surveillance period, and 14 isolates (24.1%) were resistant to imipenem. Of the 14 isolates, 9 were tested positive in Modified-Hodge test and 2 were also positive in EDTA-disk synergy test. Genes encoding OXA-23 and IMP-1 were detected in 7 and 2 isolates, respectively. In IEF studies, OXA-23 and IMP-1 enzymes had corresponding pIs at 6.7 and 9.0, respectively. Seven OXA-23-producing and 2 IMP-1-producing isolates showed the same ERIC PCR patterns.
CONCLUSION
It is concluded that 7 and 2 A. baumannii isolates from the patients in a hospital in Busan acquired resistance to imipenem by producing OXA-23 and IMP-1 beta-lactamases, respectively. The isolates producing these beta-lactamases might be originated from a common source.

Keyword

Acinetobacter baumannii; OXA-23; IMP-1; Imipenem-resistance

MeSH Terms

Acinetobacter baumannii*
Acinetobacter*
Agar
beta-Lactamases
Busan
Clinical Coding
Consensus
Humans
Imipenem
Isoelectric Focusing
Isoelectric Point
Korea
Microbial Sensitivity Tests
Molecular Epidemiology*
Polymerase Chain Reaction
Prevalence
Agar
Imipenem
beta-Lactamases