VIM-2 beta-lactamase in Pseudomonas aeruginosa isolates from Zagreb, Croatia

The worldwide spread of acquired metallo-β-lactamases (MBLs) in gram-negative bacilli has become a great concern. MBLs possess a broad hydrolysis profile that includes carbapenems and almost all extended-spectrum β-lactams. The aim of this investigation was to characterize MBLs in P. aeruginosa isolates from Zagreb, Croatia. 100 P. aeruginosa isolates with reduced susceptibility to either imipenem or meropenem were tested for the production of MBLs by E test MBL. The susceptibility to a wide range of antibiotics was determined by broth microdilution method. The presence of blaMBL genes was detected by PCR. Hydrolysis of 0.1 mM imipenem by crude enzyme preparations of β-lactamases was monitored by UV spectrophotometer.. Outer membrane proteins were prepared and analysed by SDS-PAGE. Six out of 100 isolates were positive for MBLs by E test. All strains were resistant to gentamicin, ceftazidime and cefotaxime and all except of one to imipenem. Six strains positive for MBLs in E test were identified as VIM MBLs producers by PCR. Sequencing of blaVIM genes revealed the production of VIM-2 β -lactamase in all six strains. This investigation proved the occurence of VIM-2 β-lactamase among P. aeruginosa strains from Zagreb, Croatia. VIM-2 β -lactamase with similar properties was previously described in another region of Croatia, Italy, France, Spain, Greece, Taiwan and South Korea suggesting that this type of enzyme is widespread in Mediteranean region of Europe and in Far East. Key words: meropenem, imipenem, metallo-β-lactamases, resistance, Pseudomonas aeruginosa