Antibacterial activity of garlic extracts on fish pathogenic bacteria

Aim : Aqueous and methanol extracts of Mum sativum (clove and peel) were investigated for their antibacterial properties in in-vitro assay against four marine pathogens. Aeromonas hydrophila. Vibrio anguillarum. Vibrioalginolyticus and Vibrio harveyi. Methodology : Different concentrations of methanol and aqueous garlic extracts were used in different methods including the disc-diffusion, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) assay. Results : The aqueous extract of A. sativum (clove and peel) had no antibacterial effect against the pathogenic bacteria tested, while the clove extract of methanol showed a strong inhibition activity against pathogens tested. The largest inhibition zone was observed against A. hydrophila (15.3 +/- 0.3) and the least were detected against V anguillarum (11.0 +/- 0.6) and V harveyi (11.0 +/- 0.6). The MIC and MBC values revealed that A. hydrophila was inhibited by a supernatant extract of clove at the lowest concentration of 0.6 mg ml(-1), while other pathogens were inhibited at the concentration of 0.8 and 1.0 mg ml(-1). Interpretation : This study suggests that clove extract of A. sativum has the potential to be used as a phytobiotics in controlling the growth of marine pathogens.