Antimicrobial activity of polymyxin B against non-fermentative Gram-negative bacteria in Georgia

Abstract number: 1734_27

Nanuashvili A., Kereselidze M., Davitashvili T.

Objectives: The polymyxins have activity against a wide variety of Gram-negative bacilli, including non-fermentative isolates. Polymyxins B and E were introduced into clinical practice during the 1950s for the treatment of Gram-negative infections. However, the parenteral use of these compounds was abandoned during the 1970s when better-tolerated anti-pseudomonal agents became available. The emergence of multidrug-resistant (MDR) isolates of Pseudomonas aeruginosa and Acinetobacter spp. has required the expanded systemic use of these polymyxins. The main objective of this study was to assess the activity and spectrum of polymyxin B against the non-fermentative Gram-negative bacilli isolated in Georgia.

Methods: In total, 257 isolates of Pseudomonas aeruginosa and 100 isolates of Acinetobacter spp. were collected between January 2000 and December 2005. All isolates were identified at the Microbiological Laboratory, ``Cito''. For the cultivation, microbiological identification and antimicrobial susceptibility testing ``Bio Merioux'' (France) test systems were used. Isolates exhibiting resistance to piperacillin/tazobactam, ceftazidime, cefepime, imipenem, ciprofloxacin and amikacin were categorised as MDR.

Results: Susceptibility rates for the antimicrobial agents tested ranged between 46.5% (ciprofloxacin), 64.5% (amikacyn), 69.7% (piperacillin/tazobactam), 74.5% (ceftazidime), 77.3% (cefepime) and 89.5% (imipenem) for P. aeruginosa, and between 16% (ciprofloxacin), 34% (piperacillin/tazobactam), 40% (ceftazidime), 44% (amikacin), 67% (cefepime) and 95% (imipenem) for Acinetobacter spp. Only polymyxin B demonstrated reasonable potency against Acinetobacter spp. (100% susceptible) and P. aeruginosa (98.9% susceptible).

Conclusion: Polymyxin B remains very active against clinical isolates of P. aeruginosa and Acinetobacter spp., including isolates resistant to carbapenems. Polymyxin resistance has been documented rarely, but the emergence of polymyxin-resistant P. aeruginosa and Acinetobacter spp. would pose a serious therapeutic problem, since no new antimicrobial agents are available currently for treatment of infections caused by MDR Gram-negative bacilli.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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