Abstract
Background
Acinetobacter baumannii is an aerobic, gram-negative, glucose-nonfermenting bacterium, which has emerged as a serious opportunistic pathogen. In recent years, the increasing instance of carbapenem-resistant A. baumannii producing metallo-β-lactamases (MBLs) or OXA-type β-lactamases is causing a serious clinical problem. In this study, we investigated the prevalence of Ambler class A, B, and D β-lactamases and their extended-spectrum derivatives in carbapenem-resistant A. baumannii isolates.
Methods
A total of 31 consecutive, non-duplicate, carbapenem-resistant A. baumannii were isolated from three university hospitals in the Chungcheong province of Korea. The modified Hodge and inhibitor-potentiated disk diffusion tests were conducted for the screening of carbapenemase and MBL production, respectively. PCR and DNA sequencing were performed for the detection of β-lactamase genes. We also employed the enterobacterial repetitive intergenic consensus (ERIC)-PCR method for the epidemiologic study.
Results
Twenty-three of 31 isolates harbored blaOXA-2 (51.6%), blaOXA-23 (22.6%), blaIMP-1 (48.4%), and blaVIM-2 (3.2%). All of the OXA-2-producing strains also evidenced MBLs. The strains that harbored blaOXA-23 were isolated only in hospital C, and only in a limited fashion. The ERIC-PCR pattern of the five OXA-23 strains indicated that the isolates were closely related in terms of clonality. The six strains producing IMP-1 isolated from hospital A were confirmed to be identical strains.
Conclusions
A. baumannii strains harboring IMP-1 or OXA-type β-lactamases are currently widely distributed throughout the Chungcheong province of Korea. The most notable finding in this study was that a blaOXA-2-producing A. baumannii harboring MBL, which has not been previously reported, can also lead to outbreaks.
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Table 1.
Table 2.
Isolates | Antibiotic susceptibilities | Clover-leaf | IPD | β-lactamase | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
AMK | GEN | TOB | ATM | CAZ | FEP | IPM | MEM | PIP | TZP | CIP | ||||
A1 | R | R | R | R | R | R | R | R | R | I | R | + | + | IMP-1, OXA-2 |
A3 | R | R | R | R | R | R | R | R | R | I | R | + | + | IMP-1, OXA-2 |
A4 | R | R | R | R | R | R | R | R | R | I | R | - | - | |
A5 | S | S | I | I | R | R | R | R | R | S | S | + | + | IMP-1, OXA-2 |
A6 | S | R | I | R | R | R | R | R | R | S | S | + | + | IMP-1, OXA-2 |
A7 | R | R | R | R | R | R | R | R | R | I | R | + | + | IMP-1, OXA-2 |
A8 | S | R | R | R | R | R | R | R | R | S | S | + | + | IMP-1, OXA-2 |
A9 | R | R | R | R | R | R | R | R | I | S | R | + | + | IMP-1, OXA-2 |
A10 | S | R | R | R | R | R | R | R | R | R | R | + | + | IMP-1, OXA-2 |
A11 | S | S | I | R | R | R | R | R | R | S | S | + | + | IMP-1, OXA-2 |
A12 | S | R | R | R | R | R | R | R | R | S | S | + | + | IMP-1, OXA-2 |
A14 | R | R | R | R | R | R | R | R | R | R | R | - | - | |
A15 | S | S | S | R | R | R | R | R | R | R | S | - | - | |
A16 | S | R | R | R | R | R | R | R | R | R | I | - | - | |
B25 | R | R | R | I | R | R | R | R | R | S | S | + | + | IMP-1, OXA-2 |
B75 | R | R | R | I | R | R | R | R | S | S | I | + | + | IMP-1, OXA-2 |
B297 | R | R | R | I | R | R | R | R | R | S | S | + | + | IMP-1, OXA-2 |
B814 | R | R | R | R | R | S | R | R | S | R | S | + | + | VIM-2, OXA-2 |
B852 | R | R | R | I | R | I | R | R | R | S | I | + | + | IMP-1, OXA-2 OXA-23 |
C1 | R | R | R | R | R | R | R | R | R | R | R | + | - | |
C2 | R | R | R | R | R | R | R | R | R | I | R | + | + | IMP-1, OXA-2 |
C3 | R | R | R | R | R | R | R | R | R | R | R | - | - | |
C4 | R | R | R | R | R | R | R | R | R | R | R | + | - | OXA-23 |
C5 | R | R | R | R | R | R | R | R | R | R | R | - | - | |
C6 | R | R | R | R | R | R | R | R | R | R | R | + | - | OXA-23 |
C9 | R | R | R | R | R | R | R | R | R | R | R | + | - | OXA-23 |
C13 | R | R | R | R | R | R | R | R | R | R | R | + | - | OXA-23 |
C14 | R | R | R | R | R | R | R | R | R | I | R | - | - | |
C15 | R | R | R | R | R | R | R | R | R | R | R | + | - | OXA-23 |
C16 | R | R | R | R | R | R | R | R | R | R | R | + | - | OXA-23 |
C17 | R | R | R | R | R | R | R | R | R | I | R | - | - | |
19606∗ | - | - | ||||||||||||
YMC† | + | + | VIM-2 |