Treatment of Aeromonas hydrophila and Vibrio parahaemolyticus infections in Macrobrachium rosenbergii using bioactive compounds from marine Actinomycetes – an alternative to synthetic antibiotics

Abstract

Natural products from certain marine microorganisms have been used as an alternative to antibiotics in recent times for the treatment of infectious diseases in aquaculture. Marine Actinomycetes are the most prolific secondary metabolite producers. The aim of the present study was to extract the bioactive compounds from marine Actinomycetes extracts which can be used as a bioactive feed in treating the bacterial infection in prawns. This study investigated the antibacterial potential of Actinomycetes isolated from marine sediments against two aquatic pathogens, Aeromonas hydrophila and Vibrio parahemolyticus. A total of 17 distinctive colonies were screened and amongst them, 2 showed a broad-spectrum antibacterial activity. The strains were characterized based on cultural, morphological, and biochemical methods. 16S rRNA sequencing confirmed the isolates as Microbacterium marinum and Kocuria rhizophila falling under Actinomycetes. 7 purified compounds extracted from the two strains showed a good inhibition zone of 10–17 mm against A. hydrophila and 11–21 mm against V. parahemolyticus respectively. The survival rate of Macrobrachium rosenbergii after the bioactive feed treatment was found to be 80–90 %. The immunological, biochemical and antioxidant enzymatic activities showed increased activities and disease resistance. The gene expression analysis with immune genes by qRT-PCR revealed enhanced immune response. A difference in the data was regarded as statistically significant when the p significance value was less than or equal to 5 (p ≤ 0.05). The present study developed an alternative antimicrobial therapeutic treatment as an alternative to synthetic antibiotics against aquatic bacterial pathogens that can benefit the aquaculture farmers.