Microbes play crucial role in aquaculture systems. In the present study, screening of the bacterial communities of Aeromonas sp., Vibrio sp., Staphylococcus sp., E. coli sp. and Salmonella sp. associated with shrimp, bivalves and sea cucumber revealed that Aeromonas sp. was the dominant pathogen in shrimp representing 6.33% and 11.25% of the total heterotrophic bacteria associated with shrimp surface and body, respectively. Antibacterial activity of different extracts of the invertebrate bodies and chitosan in addition to eleven attached bacterial isolates were tested. The marine bacterial isolate which was identified as Vibrio alginolyticus S10 by using 16S rDNA sequence analysis, was superior in its antibacterial activity, recording the highest activity unit of 10.24 ± 3.15 AU against A. hydrophila. The impact of probiotic V. alginolyticus S10 in improving the water quality of A. hydrophila infected Marsupenaeus japonicus culture was investigated. The histopathological study of M. japonicus tissues showed limited tissue damages observed in treatments using probiotic bacteria. Three stages of infection have been defined in infected hepatopancreas according to vacuolation, and hemolytic aggregation while intensity of infections in muscle and heart tissues was determined according to bacterial doses and hemolytic aggregation.
Vibrio alginolyticus S10, Aeromonas sp., Antibacterial, Probiotic, Marsupenaeus japonicus, Histopathology
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