Metallo-beta-lactamases in clinical Pseudomonas isolates in taiwan and identification of VIM-3, a novel variant of the VIM-2 enzyme

A total of 209 clinical isolates Pseudomonas (193 Pseudomonas aeruginosa, 1 0 P. putida, 4 P. stutzeri, and 2 P. fluorescens isolates) with reduced sus ceptibilities to imipenem and/or ceftazidime were subjected to PCR assays w ith primers specific for bla(IMP-1). bla(IMP-2), bla(VIM-1), and bla(VIM-2) and sequence analysis to identify the metallo-beta -lactamases (MBLs) prev alent among these organisms in Taiwan; and 21 isolates gave positive result s. Five isolates including two P. putida and three P. stutzeri isolates wer e found to carry bla(IMP-1) and six isolates including five P. putida and o ne P. stutzeri isolates harbored bla(VIM-2). The remaining 10 isolates were P. aeruginosa and all were found to carry a novel variant of bla,,,, desig nated bla,,,. There are only two nucleotide differences between bla(VIM-2) and bla(VIM-3), leading to two amino acid alterations. Our findings indicat e that VIM-2 and its variant have become the most prevalent metalloenzymes in Pseudomonas in Taiwan. Southern hybridization with the bla(VIM-2)-, bla( VIM-3)-, and bla(IMP-1) -specific probes revealed that only two VIM-2-produ cing P. putida isolates appeared to carry the MBL gene on plasmids. Pulsed- held gel electrophoresis showed that six VIM-3-producing P. aeruginosa isol ates and two IMP-1-producing P. stutzeri isolates were genetically related, suggesting that the spread of these MBL genes in Taiwan could be due to cl onal dissemination as well as genetic exchange between different clones.