A VIM metallo-␤-lactamase-producing Aeromonas hydrophila strain carrying an integron-borne bla VIM-4 gene was isolated from a cirrhotic patient's fecal sample in a Budapest hospital. The variable region of this integron is identical with that of a previously characterized integron from Pseudomonas aeruginosa clinical isolates in Pécs in southern Hungary.Aeromonas species are considered food-borne pathogens of emerging importance (2,7,15). Most species belonging to this genus, particularly those associated with human infections, are widely distributed in the environment, especially in freshwater, sewage, marine environments, and drinking water, and are also found in a wide range of animal and plant food products (1, 2, 5, 21). These pathogens can cause infections in both immunocompetent and -compromised patients, including gastroenteritis, bacteremia, meningitis, and skin and soft-tissue infections (9). Chromosomally mediated, inducible ␤-lactamases were recognized as the major mechanism of ␤-lactam resistance in Aeromonas hydrophila. These enzymes comprise a molecular class C cephalosporinase, a class D penicillinase, and a class B metallo-␤-lactamase (MBL) designated CphA, the last being a carbapenemase enzyme with a relatively narrow substrate profile (1,16,19,20). In this report we describe the first VIM MBL-producing A. hydrophila strain carrying an integron-borne bla VIM-4 gene.Antimicrobial disk susceptibility tests were performed on Mueller-Hinton agar (Oxoid, Basingstoke, United Kingdom) as recommended by the Clinical and Laboratory Standards Institute (6). Test disks were purchased from Oxoid. MICs were determined by the agar dilution method for ␤-lactam antibiotics and by the Etest (AB Biodisk, Solna, Sweden) for other antibiotics. To detect MBL production, the MBL Etest (AB Biodisk, Solna, Sweden) and the imipenem-EDTA disk method (23) were used and complemented with the use of ceftazidime, cefepime, cefotaxime, cefoxitin, cefoperazone, piperacillin, and piperacillin-tazobactam disks with or without 750 g EDTA. To prepare ␤-lactam-EDTA disks, 750 g EDTA in the form of a 0.5 M EDTA solution (pH 8.0) was added to a ␤-lactam disk placed on a Mueller-Hinton agar plate (3, 23).Detection of bla VIM genes and class 1 integrons by PCR and sequencing was performed as described earlier (13,14). Conjugation experiments were performed on Mueller-Hinton agar plates with the Escherichia coli J5-3 Rif r and Pseudomonas aeruginosa PAO4089Rp strains (12) as recipients. Transconjugants were selected on Mueller-Hinton agar plates containing 300 and 100 g/ml rifampin, respectively, and 32 g/ml cefotaxime or 128 g/ml ticarcillin.