Antimicrobial Properties of Brassica oleracea var. gongylodes Extracts against Fish and Human Pathogens

Abstract

Brassica oleracea var. gongylodes (Kohlrabi), a member of the Brassicaceae family, is a low, stout cultivar of the cabbage that grows almost anywhere and is used as a food and also as a traditional medicine.Due to the undesirable problems and side effects arisen from the consumption of artificial chemical compounds, extracts from various plant species, especially edible and medicinal ones, have attained appreciable interest among the research community. In this study, methanol and ethanol extracts of B. oleracea var. gongylodes were secreened for their potential antimicrobial activities against fish and human clinical and food borne pathogen microorganisms. To evaluate the antimicrobial activity of the extracts, disc diffusion and micro-dilution broth methods were used. The antimicrobial activities of the extracts were determined against 6 different fish pathogen bacteria (Lactococcus garvieae, Streptococcus agalactiae Pasteur Institute 55118, Yersinia ruckeri, Vibrio anguillarum (M1 and A4 strains, from two different companies), Vibrio alginolyticus and Aeromonas hydrophila ATCC 19570). The antimicrobial test results showed that the extracts exhibited varying degrees of antimicrobial activity on the all tested fish pathogens except V. alginolyticus. The minimal bactericidal concentration (MBC) values for the test bacteria which were sensitive to the extracts were in the range of 11.25-45.00 mg/ml. The extracts were also tested in vitro against 12 human clinical and food borne pathogen microorganisms (four gram positive bacteria, seven gram negative bacteria and one fungus). The minimal and maximal inhibition zones of methanol and ethanol extracts were in the range of 9.27-14.51 mm and 10.40-14.53 mm, respectively. Furthermore, some of these plants extracts were more effective than traditional antibiotics (Ampicillin, Amikacin and Gentamicin) to combat the pathogenic microorganisms studied. The results presented here may suggest that methanol and ethanol extracts of B. oleracea var. gongylodes possess antimicrobial property, and therefore, they may be a potential source of a natural preservative in feed/food and pharmaceutical industry.