Antimicrobial resistance pattern of Pseudomonas aeruginosa in clinical isolates from ICU patients

Abstract

Introduction: Pseudomonas aeruginosa remains one of the most important pathogens in the nosocomial setting, where it is a common causative agent of bacteremia [1,2]. The aim of this study was to evaluate the antimicrobial resistance of Pseudomonas spp. strains isolated from inpatients hospitalized in the ICU of our hospital throughout a 3-year period. Methods: A total of 175 clinical isolates of Pseudomonas spp. collected from January 2006 to December 2008 were investigated in this study. Each isolate was obtained from a different patient. Identification and routine antibiograms of the isolates were carried out using the Vitek 2 automated System (BioMerieux®, Marcy I'Etolie, France). The minimum inhibitory concentrations of imipenem, meropenem and colistin were also determined by the agar dilution method according to Clinical Laboratory Standards Institute guidelines. Results: The isolates included in our study originated from blood cultures 70 (40%), urine 53 (30.3%), bronchial aspirates 23 (13.1%), central venous catheters 18 (10.3%) and others 11 (6.3%). The resistance rates changed from 2006 to 2008 as follows: amikacin: 72 to 83%, aztreonam: 90 to 95%, ceftazidime: 81 to 89%, ciprofloxacin: 79 to 85%, colistin: 0 to 0%, meropenem: 72 to 83%, imipenem: 72 to 83%, netilmicin: 72 to 83%, piperacillin/tazobactam: 71 to 80%, tobramycin: 72 to 83%, ticarcillinlin/clavulanic acid: 71 to 80%. Conclusions: Pseudomonas spp. infections are particularly serious for incubated ICU patients with 40 to 50% mortality rates. In our hospital, the percentage of Pseudomonas spp. multiresistant isolates has increased dramatically over the past 3 years. The majority of isolates were resistant to 15 or more antibiotics. What is most worrying is the fact that there is a prevalence of a multiresistant phenotype that was only sensitive to colistin. The emergance and rapid spread of multidrug-resistant isolates of Pseudomonas spp. are of great concern worldwide. It is necessary to limit the overuse of antibiotics and to implement a new antibiotic policy.