Prevalence of Metallo-beta-lactamases in Imipenem-non-susceptible Pseudomonas aeruginosa and Acinetobacter baumannii / 대한임상미생물학회지

BACKGROUND: Metallo-beta-lactamases (MBLs) have been reported in gram negative bacilli and are becoming increasingly important clinically because the enzymes hydrolyse almost all beta-lactams, including carbapenems. Thus, the present study was conducted to determine the prevalence of MBL types in imipenem-nonsusceptible Pseudomonas aeruginosa and Acinetobacter baumannii isolated from a tertiary teaching hospital. METHODS: Imipenem-nonsusceptible strains, 128 P. aeruginosa and 93 A. baumannii, were collected from clinical specimens. Identification and susceptibility tests were determined by Vitek GNI and GNS cards. MBL production was determined by modified Hodge test and imipenem-EDTA synergy test. Multiplex PCR amplification of MBL genes including blaIMP-1, blaVIM-1 and blaVIM-2 were performed. RESULTS: Thirty-one P. aeruginosa (24.2%) isolates and 3 A. baumannii (3.2%) were found to be MBL producers. In P. aeruginosa, 20 (15.6%) and 11 (8.6%) isolates were positive for blaIMP-1 and blaVIM-2, respectively whereas 1 (1.0%) and 2 (2.2%) isolates in A. baumannii, respectively. CONCLUSION: IMP-1 is more prevalent MBL type than VIM-2 among imipenem-nonsusceptible P. aeruginosa unlike in other studies. Larger numbers of isolates and sequential studies are strongly recommended for the useful evaluation and monitoring of MBL production in the hospital setting to infection-control.

Characterization of Class 1 Integrons in Metallo-beta-lactamase-producing Pseudomonas aeruginosa / 대한임상미생물학회지

BACKGROUND: The genes of metallo-beta-lactamase (MBL), a powerful carbapenemase, are carried as a part of the mobile gene cassettes inserted into integrons playing an important role in rapid dissemination of antibiotic resistance genes among bacterial isolates. In this study, we investigated carbapenemase genes and class 1 integrons integrated into the gene cassettes in imipenem-non susceptible P. aeruginosa. METHODS: From July 2006 to March 2008, 81 consecutive, non-duplicate, imipenem-non susceptible P. aeruginosa were isolated at Chungnam National University Hospital in Chungcheong province of Korea. The modified Hodge and double disk synergy tests were conducted for the screening of carbapenemase and MBL production, respectively, and PCR and DNA sequencing were performed for the detection of carbapenemase genes and class 1 integron gene cassettes. We also employed the repetitive element sequence-based (Rep)-PCR method for an epidemiologic study. RESULTS: MBLs were detected in 13.6% (11/81) of imipenem-non susceptible P. aeruginosa. Ten isolates were found to carry blaIMP-1, whereas 1 isolate was found to carry a blaVIM-2. All of the IMP-1-producing strains harbored 4.0 kb class 1 integron containing chloramphenicol, aminoglycoside, and beta-lactam- resistant genes. However, blaIMP-1 was not detected at class 1 integron. A 2.5 kb class 1 integron harboring blaVIM-2 was detected in a VIIM-2- producing strain. One identical pattern was observed in ten IMP-1 producing strains. CONCLUSION: IMP-1 producing P. aeruginosa strains are currently distributed throughout Chungcheong province of Korea. In particular, all of the strains harbored class 1 integrons containing variant antibiotic resistance gene cassettes.

Characteristics of Acquired beta-lactamase Gene in Clinical Isolates of Multidrug-resistant Pseudomonas aeruginosa / 대한임상미생물학회지

BACKGROUND: Recently, there have been reports of infections with multidrug-resistant Pseudomonas aeruginosa. To determine the mechanism of the resistance, we investigated the prevalence of Ambler class A and D beta-lactamases, their extended-spectrum derivatives, and class B and D carbapenemase in multidrug-resistant P. aeruginosa isolates. METHODS: During the period of March 2006 to May 2007, clinical isolates of multidrug-resistant P. aeruginosa were collected from patients in Chungnam National University Hospital, Daejeon, Korea. Inhibitor-potentiated disk diffusion tests were used for the screening of metallo-beta-lactamase (MBL) production. PCR and DNA sequencing were conducted for the detection of beta-lactamase genes. We also employed the enterobacterial repetitive intergenic consensus (ERIC)- PCR method for an epidemiologic study. RESULTS: A total of 37 consecutive, non-duplicate, multidrug-resistant P. aeruginosa were isolated. Twenty- nine of 37 isolates harbored blaOXA-10 (56.8%), blaOXA-2 (18.9%), and blaOXA-1 (5.4%). Only one isolate produced IMP-1, and it also harbored blaOXA-1. None harbored Ambler class A beta-lactamase or class D carbapenemase. The strains producing OXA type beta-lactamases showed a significantly higher resistance to aminoglycoside compared to non-producers. The ERIC-PCR pattern of the 19 OXA-10 producing strains indicated that the isolates were closely related in terms of clonality. CONCLUSION: OXA type beta-lactamases are the most prevalent among the acquired beta-lactamases produced by multidrug-resistant P. aeruginosa isolated at a university hospital in Chungcheong Province. Besides beta-lactam antibiotics, the strains harboring OXA type beta-lactamase showed a significantly higher resistance to aminoglycoside and qunolone.