Evaluation of antimicrobial effect of hops extracts on intramacrophages Brucella abortus and B. melitensis

Introduction and objective: Brucellosis is a zoonosis disease among animal and human, and has been endemic in Iran. The most important virulence factors of Brucella are related to their capability of intraphagocytic survival. Because of the side effects of brucellosis treatment regime, it is necessary to find new antimicrobial agents. The hop plant (Humulus lupulus) extract reported as having antimicrobial effects. The present study evaluated the antimicrobial activity of hops extracts against Brucella abortus 544 and B. melitensis 16M. Materials and methods: Hops extracts were prepared in water, acetone and ethanol. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for two strains of Brucella determined by broth macrodilution and agar well diffusion methods. Effect of extracts on intramacrophge surviving of Brucella strains studied on cell culture of mouse peritoneal macrophages. Results: Results indicated that MIC for aqueous extract was 1:80 (0.625mg/ml) and for acetonic and ethanolic extracts was 1:160 (0.05mg/ml). MBC for aquatic extract was 1:40 (1.2mg/ml) and for two other extracts was 1:80 (0.1mg/ml). In cell culture results indicated that all of extracts were effective and eradicated intramacrophage Brucella strains in 1:40 (1.2mg/ml for aqueous and 0.2mg/ml for ethanolic and acetonic extracts), 1:80 (0.625mg/ml for aqueous and 0.1mg/ml for ethanolic and acetonic extracts) and 1:160 (0.312mg/ml for aqueous and 0.05mg/ml for ethanolic and acetonic extracts) of extracts dilutions after 24h. Conclusion: Overall this study indicated that aquatic, acetonic and ethanolic extracts of hops showed antimicrobial effect against B. abortus and B. melitensis, therefore, they are useful in the treatment of brucellosis.