Molecular Epidemiology of Carbapenem-Resistant Pseudomonas aeruginosa Clinical Strains Isolated from Western Algeria Between 2009 and 2012

Abstract

Infections caused by carbapenem-resistant Pseudomonas aeruginosa strains represent a major therapeutic and epidemiological problem. The aim of this study was to characterize carbapenem resistance in 89 clinical strains of P. aeruginosa isolated from three hospitals in western Algeria between October 2009 and November 2012. Minimum inhibitory concentrations (MICs) of imipenem were determined by the Etest method. Screening for metallo-β-lactamase (MβL) was performed using Etest MβL strips, and a PCR was conducted to detect carbapenemase-encoding genes. The amplification of the oprD gene followed by a sequencing reaction was performed for all strains resistant to imipenem. The clonality of 53 P. aeruginosa strains was demonstrated using multilocus sequence typing (MLST). Among the 89 isolates, 35 (39.33%) were found to be resistant to IMP (MICs ≥16 μg/ml). The blaVIM-2 gene was detected in two strains. The remaining imipenem-resistant isolates showed the presence of oprD mutations. The MLST analysis differentiated strains into various clones and the strains from the same clone had an identical sequence of the oprD gene. We report the second detection in 2010 of blaVIM-2 in Algerian P. aeruginosa strains. We also found that oprD mutations were the major determinant of high-level imipenem resistance. We demonstrate that these oprD mutations can be used as a tool to study the clonality in P. aeruginosa isolates.