Molecular characterisation of the metallo-β-lactamase genes in imipenem-resistant Gram-negative bacteria from a university hospital in southern Taiwan

In this study, 260 non-replicate imipenem-resistant Gram-negative bacteria isolated between January 2002 and December 2006 were subjected to a screening test for detection of metallo-beta-lactamase (MBL) using the Etest containing imipenem and ethylene diamine tetra-acetic acid (EDTA). Among the 260 strains, 123 (47.3%) appeared to produce MBL. Of these 123 strains, 113 (91.9%) were found by polymerase chain reaction (PCR) to carry MBL genes of types bla(VIM-2), bla(VIM-3), bla(VIM-11) (bla(VIM-11a)), bla(IMP-8) and novel bla(IMP-24). One strain of Serratia marcescens harboured two MBL genes (bla(VIM-11) and bla(IMP-8)) simultaneously. Of the 123 strains, 116 strains (94.3%) carrying the intI1 gene and 21 strains carrying integron-associated bla(VIM-3), bla(VIM-11) and bla(IMP-8) genes were identified among Acinetobacter baumannii, Pseudomonas aeruginosa, Acinetobacter haemolyticus and S. marcescens. Using pulsed-field gel electrophoresis (PFGE) and Southern hybridisation with the bla(VIM) gene probe for I-CeuI-digested genomic DNA, P. aeruginosa 9527 strain harboured two class 1 integron-associated MBL genes in the chromosome, including bla(VIM-3)-orf2-aacA4 and novel bla(VIM-3)-orf2-aacA4-aadB-aacA4. This is the first description of the bla(VIM-11) gene spreading among P. aeruginosa and A. baumannii strains in southern Taiwan. This finding suggests that clinical spread of this bla(VIM-11) gene is a matter of great concern for carbapenem resistance in southern Taiwan. Crown Copyright (C) 2008 Published by Elsevier B. V. on behalf of International Society of Chemotherapy. All rights reserved.