Pezhman Karami - Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
Mohammad Yousef Alikhani - Department of Microbiology, Besat Hospital, Hamadan University of Medical Sciences, Hamadan, IR, Iran
Dara Dastan - Department of Pharmacognosy and Pharmaceutical Biotechnology, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran

Introduction and Obejectives: The rapid increase of drug resistance and failure of existing antibiotics to treat infections caused by Pseudomonas aeruginosa MDR strains, introducing the new therapeutic combination is needed. This study aimed to evaluate the synergistic effects of cinnamon extracts and honey against multidrug-resistant strains of Pseudomonas aeruginosa isolated from burn ward. Materials and Methods: The minimum inhibitory concentration (MIC) and minimum bactericidal concentrations (MBC) of each antibiotic (Gentamicin and Ciprofloxacin) alone or in combination with the aqueous and alcoholic extracts of cinnamon and honey was determined by broth microdilution method for clinical and environmental isolates of P.aeruginosa based on the CLSI guidelines. The synergistic effect of combinations was evaluated using a checkerboard test and FICi evaluation. Data analyzed using SPSS software by Chi-square and Fisher’s exact tests. Results: The means MIC for Cinnamomum zeylanicum Alcoholic extract-Honey(CZ.A.H), Cinnamomum zeylanicum watery extract-Honey(CZ.W.H), Ciprofloxacin-Cinnamomum zeylanicum watery extract(CP.CZ.W), Gentamicin-Cinnamomum zeylanicum watery extract(GM.CZ.W), Ciprofloxacin-Cinnamomum zeylanicum Alcoholic extract(CP.CZ.A), Gentamicin-Cinnamomum zeylanicum Alcoholic extract(GM.CZ.A), Ciprofloxacin-Honey(CP.H), Gentamicin-Honey(GM.H) against MDR strains were as 6.80, 15.63, 18.62, 5.84, 10.70, 3.84 and 36.88 μg/mL, respectively. The means MBC for CZ.A.H, CZ.W.H, CP.CZ.W, GM.CZ.W, CP.CZ.A, GM.CZ.A, CP.H, and GM.H against MDR strains were as 13.17, 30.25, 29.63, 31.52, 11.32, 21.28, 60.11and 70.03μg/ml, respectively. According to the FICi results, 14.1, 1.3, 3.8, 19.2, 32.1, 29.5, 9 and 9% of isolates had the synergism for CZ.A.H, CZ.W.H, CP.CZ.W, GM.CZ.W, CP.CA.A, GM.CZ.A, CP.H and GM.H combinations, respectively. Conclusion: This study showed the acceptable synergistic effect of aqueous and alcoholic extracts of Cinnamon and honey in combination with Ciprofloxacin and Gentamicin.

Synergistic effect, cinnamon, honey, Pseudomonas aeruginosa, burn ward