Invitro effect of juglans regia li. stem bark hydroalcoholic extract on some bacterial pathogens of fish

Fish farmers are losing millions of dollars annually due to the large scale mortality of fish due to diseases caused by antibiotic resistance pathogens. Plant secondary metabolites show activity in the micro to submicromolar range to Gram-positive species. Plant extracts decrease the selective pressure for developing antibiotic resistance. Hence, in the present study antibacterial effect of hydroalcoholic extract of Juglans regia Li. compound against Aeromonas hydrophila, Yersinia ruckeri, Streptococcus iniae, Staphylococcus aureus and Salmonella typhimurium were screened. By standard protocol, hydroalcoholic extract of Juglanse regia Li. stem bark in pharmacology department of Shahid Chamran Veterinary School was prepared. To determine the positive control for each bacterial, antibiogram was done. In vitro evaluation of antibacterial effect of extract was done by disc diffusion method (Kirby bauer) and minimum inhibitory concentration was determind by E-test and macrodilution method. According to result in this study, clear inhibition zone compared with the positive control was seen about A.hydrophila and Y.ruckerii. But no strong effect on other studied bacteria was observed. By E-test, minimum inhibitory concentration of extract in Y.ruckerii and A.hydrophila was evaluated,3.9 and 12 mg/ml,respectively. Minimum inhibitory concentration of extract in Y.ruckerii and A.hydrophila by macrodilution was 3.9 and 62.5 mg/ml and minimum bactericidal concentration was 7.81 and 125 mg/ml, respectively. Y.ruckerii and A.hydrophila are important bacteria in the aquaculture industry and hydroalcoholic extract of this plant was effective on them but more work should be done on its safety and toxicity. Other studied bacteria which extract had any effect on them, should be examined with other form (alcoholic or aqueous) of stem bark Juglans regia Li. extract because type of solvent or the method of preparation can affect antibacterial activity of extract.