Increasing prevalence of imipenem-resistant Pseudomonas aeruginosa and molecular typing of metallo-β-lactamase producers in a Korean hospital

The types of metallo-beta-lactamases (MBLs), integrons, and genetic relatedness among Pseudomonas aeruginosa were investigated with a recent high prevalence of imipenem resistance in a Korean hospital. During 2000-2003, a total of 116 nonduplicate imipenem-resistant P. aeruginosa isolates were analyzed by PCR and DNA sequencing to detect of bla(IMp-1), bla(VIM-1), bla(VIM-2), bla(SPM-1), intI1, intI2, and intI3 genes. Among them, MBL-producing isolates were evaluated for genetic relatedness using pulsed-field gel electrophoresis (PFGE) profiles. Of 116 isolates, 21 (18.1 %) carried bla(VIM-2) gene with the intI1 gene. Analysis of VIM-2 procuders by PFGE grouped 21 isolates into eight different clusters. Six of eight cluster I strains, all of four cluster 11 strains, and all of three cluster III strains were isolated in 2000, 2002, and 2003, respectively. Data concluded that P. aeruginosa carrying bla(VIM-2) with a class 1 integron was the only type among MBLs. A hospital outbreak by VIM-2 producers occurred annually, which could be at least a part of a recent high prevalence of imipenem resistance.