Spread of integron-associated VIM-type metallo-beta-lactamase genes among imipenem-nonsusceptible Pseudomonas aeruginosa strains in Greek hospitals

Abstract

Fifty-eight imipenem-nonsusceptible (MIC >or= 8 microg/ml) Pseudomonas aeruginosa strains isolated during May 2001 in 15 Greek hospitals were studied. Thirty-six isolates derived from nine hospitals carried VIM-type metallo-beta-lactamase genes, as found by PCR. In 34 isolates, bla(VIM) was associated with class 1 integrons of various sizes. DNA sequencing indicated the presence of bla(VIM-2) gene cassettes in a variety of integron structures. Random amplified polymorphic DNA typing suggested diversity of the bla(VIM)-positive strains. Synergy between 2-mercaptoacetic acid and imipenem indicated carbapenemase activity in 26 bla(VIM)-positive strains.

FIG. 1.

RAPD patterns of P. aeruginosa isolates carrying bla_VIM. Lane A, RAPD type 6 (Table 2); lanes B and C, RAPD type 4; lanes E and F, RAPD type 10; lanes G and H, RAPD type 14; lanes I and J, RAPD type 1; lanes K and L, RAPD type 3. Molecular weight markers (100-bp DNA Ladder Plus; MBI Fermentas) are in lane D. The RAPD pattern similarity of the isolates in lanes I and J was confirmed in repeated experiments.