association between metallo-β-lactamases and integrons with multi-drug resistance in pseudomonas aeruginosa isolates

pseudomonas aeruginosa is among the most important pathogens in the nosocomial infections. a genetic mobile element, the integron, is one of the major agents involved in dissemination of multi-drug resistance among gram negative bacteria. during a descriptive study from october 2009 to august 2010, some 130 p. aeruginosa clinical isolates were collected from different wards of three hospitals in tehran. the minimal inhibitory concentration (mic) of 4 antibiotics conventionally used in clinical settings against the isolates was determined by e-test method. also, the existence of integron classes and metallo-β-lactamases (blavim-1, blaimp-1, and blavim-2) were investigated by pcr assay. out of 130 isolates, 74 (56.9%) carried class 1 integron. none of the isolates harbored integrons class 2 and 3. also, the blavim-1 gene was detected in 10 (13.3%) high level ceftazidime and imipenem- resistant isolates that carried class 1 integrons. the blaimp-1 and blavim-2 genes were not detected in any isolates. in the present study, the antibiotic resistance rates in class 1 integron-positive isolates of p. aeruginosa were significantly higher than those lacking this integron , e.g., 82.6% resistance versus 17.3% sensitivity to ceftazidime. also, 13.3% of ceftazidime and imipenem resistant isolates was metallo-β-lactamase producer. this indicates that all metallo-β-lactamase genes are correlated with class 1 integrons. these results imply that the blavim-1 gene has been presumably dispersed into p. aeruginosa isolates with the help of class 1 integron element.