Outbreaks of imipenem resistant Acinetobacter baumannii producing OXA-23 beta-lactamase in a tertiary care hospital in Korea.
OBJECTIVE
Since November 2006, imipenem-resistant Acinetobacter baumannii isolates have increased in Kyung Hee University Hospital in Seoul, Korea. The purpose of this study was to determine the genetic basis and molecular epidemiology of outbreak isolates.


METHODS
Forty-nine non-repetitive isolates of the 734 IRAB strains were investigated in order to determine their characteristics. The modified Hodge and the ethylenediaminetetraacetic acid (EDTA)-disk synergy test were performed for the screening of carbapenemase and metallo-beta-lactamase production. Multiplex polymerase chain reaction (PCR) assays were performed for the detection of genes encoding for OXA-23-like, OXA-24-like, OXA-58-like and OXA-51-like carbapenemase. Pulsed-field gel electrophoresis (PFGE) was performed for strain identification.


RESULTS
All isolates showed 100% resistance to ciprofloxacin and gentamicin, 97.9% resistance to cefepime, piperacillin/tazobactam, aztreonam, ceftazidime and piperacillin, 93.9% resistance to tobramycin and 57.1% resistance to amikacin. All of the 49 isolates (100%) showed positive results in the modified Hodge test and negative results in the EDTA-disk synergy test. They all (100%) possessed the encoding gene for an intrinsic OXA-51-like carbapenemase and an acquired OXA-23-like carbapenemase in the multiplex PCR assay. PFGE patterns revealed that all isolates were clonally related from A1 to A14.


CONCLUSIONS
It is concluded that all of the 49 IRAB isolates acquired resistance to imipenem by producing OXA-23 carbapenemase and they might have originated from a common source.
Yang
Hee Young
HY
Department of Laboratory Medicine, College of Medicine, Kyung Hee University, Seoul, Korea.
Lee
Hee Joo
HJ
Suh
Jin Tae
JT
Lee
Kyeong Min
KM
D000151:Acinetobacter Infections / Q000453:epidemiology / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000077723:Cefepime; D002511:Cephalosporins / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics / Q000502:physiology; D016521:Electrophoresis, Gel, Pulsed-Field; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D015378:Imipenem / Q000494:pharmacology*; D007723:Korea / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D005839:Gentamicins; D047090:beta-Lactams; D002939:Ciprofloxacin; D015378:Imipenem; D000077723:Cefepime; D001618:beta-Lactamases