Carbapenem resistance determined by metalloenzymes in clinical isolates of Pseudomonas aeruginosa

: Carbapenem resistance in clinical isolates of P. aeruginosa has risen notably in recent years. P. aeruginosa has different mechanisms for carbapenem resistance, such as decreased levels of OprD or overexpression of the MexAB-OprM efflux system. Also, the emergence of metallo-beta-lactamases (MBL)-producing bacteria is becoming a severe therapeutic problem. The aim of this study was to determine MBL presence in clinical isolates of P. aeruginosa: 133 with MIC > or =4 mg/l for imipenem and/or meropenem were selected. We studied the sensitivity to different antibiotics in these strains. Tobramycin (26.3%) and colistin (17.3%) were the most active antibiotics. To determine the presence of MBL, we used the E-test with imipenem/imipenem plus EDTA and disk-agar diffusion, also using EDTA as an MBL inhibitor. As a result of the screening test to evaluate the presence of MBL, we obtained four out of 133 strains as probable producers of metalloenzyme. These four strains were positive for the VIM-like gene as determined by a polymerase chain reaction method.