In vitro synergistic effect of ciprofloxacin with aminoglycosides against multidrug resistant-Pseudomonas aeruginosa

Pseudomonas aeruginosa is an increasingly prevalent nosocomial human pathogen. Infections with multidrugresistant (MDR) P. aeruginosa are currently a treatment challenge and requires search for better treatment options. Purpose of study: To determine in vitro synergistic effect of ciprofloxacin in combination with amikacin and gentamicin against MDR P. aeruginosa clinical isolates. Methods: Antibiotic resistance pattern of 100 identified clinical isolates of P. aeruginosa was determined against eight antibiotics by disc diffusion method at Microbiology Laboratory, Holy Family Hospital, Rawalpindi. For 30 selected MDR isolates, minimum inhibitory concentrations (MICs) of amikacin and gentamicin were determined separately by agar diffusion method followed by combined activity of ciprofloxacin with amikacin and gentamicin by checkerboard agar dilution technique. Results: Antibiotic resistance pattern of P. aeruginosa isolates was; gentamicin and carbenicillin (94%), amikacin and piperacillin (92%), ceftazidime (90%), colistin (87%), ciprofloxacin (79%) and imipenem (72%). MICs against 30 selected MDR isolates ranged from 32 to ≥128μg/ml for amikacin, and ≥128μg/ml for gentamicin. Synergistic effect was observed in 12/30(40%) isolates for AK+CIP and in 05/30 (16.7%) for CN+CIP. Conclusion: Ciprofloxacin in combination with amikacin and gentamicin showed synergistic effect and no antagonistic effect against MDR P. aeruginosa.