Prevalence and molecular epidemiology of imipenem-resistant Pseudomonas aeruginosa carrying metallo-beta-lactamases from two central hospitals in Portugal.

Metallo-beta-lactamases (MBLs) can confer broad-spectrum beta-lactam resistance, including carbapenems. The aim of this work was to document the occurrence of MBLs in 122 imipenem-resistant Pseudomonas aeruginosa isolates collected in two Portuguese central hospitals, to determine their antimicrobial susceptibility, and to observe if there were intra- and interhospital epidemic spread. About 20.5% of these isolates presented blaVIM-2, which was found to be widespread in both hospitals. Clonal diversity was observed within hospitals, and no interhospital spread was observed. Ten of the blaVIM-2-positive isolates (44%), from both hospitals, presented one or two class 1 integrons. Two of those contained a VIM-2 gene, one from each hospital, which is indicative for the possibility of MBL gene transfer. No interhospital spread of integrons was observed. Regular screening and surveillance is needed to prevent spread of this worrisome resistance determinant.