In-vitro efficacy of synergistic antibiotic combinations in multidrug resistant Pseudomonas aeruginosa strains.
OBJECTIVE
Combination antibiotic treatment is preferred in nosocomial infections caused by Pseudomonas aeruginosa (P. aeruginosa). In vitro synergism tests were used to choose the combinations which might be used in clinic. The aim of this study was to investigate the synergistic efficacy of synergistic antibiotic combinations in multidrug resistant P. aeruginosa strains.


METHODS
Synergistic efficacies of ceftazidime-tobramycin, piperacillin/tazobactam-tobramycin, imipenem-tobramycin, imipenem-isepamycin, imipenem-ciprofloxacin and ciprofloxacin-tobramycin combinations were investigated by checkerboard technique in 12 multiple-resistant and 13 susceptible P. aeruginosa strains.


RESULTS
The ratios of synergy were observed in ceftazidime-tobramycin and piperacillin/tazobactam-tobramycin combinations as 67%, and 50%, respectively, in resistant strains, whereas synergy was not detected in other combinations. The ratios of synergy were observed in ceftazidime-tobramycin, piperacillin/tazobactam-tobramycin, imipenem-tobramycin, imipenem-ciprofloxacin and imipenem-isepamycin combinations as 31%, 46%, 15%, 8%, 8%, and respectively, in susceptible strains, whereas synergy was not detected in ciprofloxacin-tobramycin combination. Antagonism was not observed in any of the combinations.


CONCLUSIONS
Although the synergistic ratios were high in combinations with ceftazidime or piperacillin/tazobactam and tobramycin, the concentrations in these combinations could not usually reach clinically available levels. Thus, the solution of the problems caused by multiple resistant P. aeruginosa should be based on the prevention of the development of resistance and spread of the causative agent between patients.
Dundar
Devrim
D
Department of Clinical Microbiology, Kocaeli University, Faculty of Medicine, Kocaeli, Turkey. devrimdundar@hotmail.com
Otkun
Metin
M
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002442:Ceftazidime / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D004357:Drug Synergism; D015378:Imipenem / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D000078142:Tazobactam; D014031:Tobramycin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D015378:Imipenem; D010397:Penicillanic Acid; D002442:Ceftazidime; D000078142:Tazobactam; D014031:Tobramycin; D010878:Piperacillin