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

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%.

Conclusion

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.