Antibacterial Activity of Coastal Plants and Marine Sponges from Kei Island Indonesia against Bacterial Fish Pathogens

Objective: The objective of this study was to investigate the antibacterial activity of coastal plants and marine sponges extracts against fish bacterial pathogens. Methods: Samples were extracted by maceration and the extracts were examined for their antibacterial activities against Streptococcus sp. BJ0509, Staphylococcus aureus ATCC 6538, Aeromonas hydrophila BA03 and Vibrio parahaemolyticus 29S by means of paper disc diffusion method. Active extracts were partitioned and purified by column chromatography. The purified substance was tested for Minimum Inhibitory Concentration (MIC) against seven bacterial fish pathogens namely Streptococcus sp., Vibrio parahaemolyticus, V. alginolyticus, V. harveyi, Photobacterium damselae, Aeromonas hydrophila and A. dhakensis. Results: The highest antibacterial activity against all bacteria used in the assay was demonstrated by OKA 6, a bark extract sample of a coastal plant, Diospyros maritima. It showed a diameter of inhibition zones against Streptococcus sp. BJ0509, S. aureus ATCC 6538, A. hydrophila BA03 and V. parahaemolyticus 29S of 19, 33, 18, and 18 mm, respectively. The column chromatography fraction of OKA 6 inhibited the growth of S. aureus ATCC 6538 with MIC of 3.125 μg/mL. The MIC of this fraction against seven bacterial fish pathogens ranged < 0.098 to 3.125 μg/mL. The antibacterial activity of partially purified substance obtained from column chromatography fractionation of OKA 6 was higher than those of oxytetracycline and kanamycin. Conclusions: This result indicates that antibacterial activity of the partially purified substance is potentially higher than those of the commercial antibiotics tested. It further indicates that OKA 6 extract from D. maritima can serve as a promising resource for the development of therapeutic agents against bacterial infections in aquaculture.