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 ۲۰۰۹ to August ۲۰۱۰, some ۱۳۰ P. aeruginosa clinical isolates were collected from different wards of three hospitals in Tehran. The Minimal inhibitory concentration (MIC) of ۴ 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-۱, blaIMP-۱, and blaVIM-۲) were investigated by PCR assay. Out of ۱۳۰ isolates, ۷۴ (۵۶.۹%) carried class ۱ integron. None of the isolates harbored integrons class ۲ and ۳. Also, the blaVIM-۱ gene was detected in ۱۰ (۱۳.۳%) high level ceftazidime and imipenem- resistant isolates that carried class ۱ integrons. The blaIMP-۱ and blaVIM-۲ genes were not detected in any isolates. In the present study, the antibiotic resistance rates in class ۱ integron-positive isolates of P. aeruginosa were significantly higher than those lacking this integron , e.g., ۸۲.۶% resistance versus ۱۷.۳% sensitivity to ceftazidime. Also, ۱۳.۳% of ceftazidime and imipenem resistant isolates was metallo-β-lactamase producer. This indicates that all metallo-β-lactamase genes are correlated with class ۱ integrons. These results imply that the blaVIM-۱ gene has been presumably dispersed into P. aeruginosa isolates with the help of class ۱ integron element.

Keywords:

β-lactam , Integron , Antibiotic resistance , Metallo-β-lactamase , Pseudomonas aeruginosa