Resistance to colistin and carbapenems with detection of class 1 integrons on Pseudomonas aeruginosa clinical isolates

Abstract number: p540

Platsouka  E., Kraniotaki  H., Tourouki  G., Doga  V., Perivolioti  E., Kanellos  K., Kalogeras  G., Paniara  O.


Metallo-beta-lactamases (MBLs) are emerging resistance determinants in Gram-negative nosocomial pathogens, including Pseudomonas aeruginosa. It is known, that colimycin (colistin), the old polymyxin derivative is active in vitro against the pan-resistant P. aeruginosa strains. In this work, we present an outbreak due to colistin and carbapenem resistant P. aeruginosa in an Intensive Care Unit (ICU) of a Greek tertiary hospital.


Six multi-resistant P. aeruginosa isolates were recovered from four patients over a two-week period between September and October 2005, in our ICU. The source of the specimens was: 1 from blood culture, 2 from bronchial secretions, 1 from pleural fluid, 1 from pus and 1 from IV catheter. Commercial ID panels identified the strains and susceptibility to a broad panel of antimicrobial agents was determined by broth microdilution method according to CLSI guidelines. E-test also determined resistance to colistin and carbapenems. Isolates were investigated for the presence of the blaVIM-1 allele by PCR. Class 1 integrons were detected and molecularly characterized by sequencing.


All isolates were found resistant to the following antimicrobial agents tested: aminoglycosides amikacin, gentamicin, tobramycin, netilmicin-, piperacillin, piperacillin/tazobactam, ticarcillin, ticarcillin/clavoulanate, carbapenems imipenem, meropenem, quinolones ciprofloxacin, ofloxacin, pefloxacin, moxifloxacin-, trimethoprim/sulfa and colistin. Three isolates were found susceptible to aztreonam with MIC of aztreonam 2 mcg/ml. The blaVIM-1 gene was detected in all strains. The same class 1 integron was found in all strains. Its sequence analysis revealed the presence of other antibiotic resistance genes, apart from the blaVIM-1 allele.


This is a rare report of a nosocomial outbreak caused by colistin resistant P. aeruginosa producing MBL. Resistance to colistin was correlated with the increased use of colistin over the last year in ICU, due to prevalence of MBL mediated carbapenem resistance in P. aeruginosa in ICU patients. All isolates harboured class 1 integrons, which means a rapid spread of the resistant genes in nosocomial environment. Control measures (hand hygiene and restriction of colistin use) resulted to disappear the above colistin resistant P. aeruginosa isolates.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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