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The antibacterial activity of individual and mixed medicinal plant compounds, azadirachtin (Az), camphor (Ca) and curcumin (Cu), was tested at 100, 200, 300, 400, 500, 600 and 700 ppm (mg L−1) against fungal fish pathogen, Aphanomyces invadans, in vitro. At the lower concentrations between 100 and 300 ppm, the mixture of the tri‐herbal (Az+Ca+Cu) compound yielded a higher (P>0.05) zone of inhibition (ZI) of 7 mm than the positive control; the maximum ZI values (8–15 mm) were realized between 400 and 700 ppm (P<0.05). At the lowest minimum inhibitory concentration (MIC) the tri‐herbal compound (100 ppm) yielded 13 colony‐forming units; hence, this dose can be effectively used at the lowest concentration of 100 mg L−1 to ward off the growth of A. invadans in vitro. In Cirrhina mrigala, intramuscular administration (100 μL) of the selected doses of 100, 400 and 700 ppm (mg L−1) significantly enhanced (P<0.05) the serum lysozyme activity (Ly), production of reactive oxygen species and reactive nitrogen species (RNS or NO) by peripheral blood leucocytes on the 10th, 20th and 30th day. A priori administration of the compound in the fish (100 ppm on 30th day) decreased the percentage mortality when challenged with the pathogen while in the untreated group the mortality increased (P<0.05). This study indicates that intramuscular administration of the tri‐herbal compound Az+Ca+Cu at a concentration of 100 ppm could augment the immune response in C. mrigala against A. invadans.

Present study aim to evaluate the antimicrobial, antioxidant and cytotoxic potential of crude extract of Marine Streptomyces carpaticus MK-01 isolated from seawater collected from Daejeong-cost of Jeju Island. About 24 actinomycetes strains were isolated and subjected to morphological and molecular analysis that confirmed the isolate as S. carpaticus MK-01. Crude ethyl acetate extract of MK-01 strain showed extensive antibacterial activity against Gram-positive fish pathogenic bacteria namely Streptococcus iniae and S. parauberis with a maximum zone of inhibition (0.92±0.03mm) was recorded against S. parauberis at the minimum extract concentration (3.12µg/ml