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In the fields of microbial, plant and animal sciencesEmergence of antimicrobial resistance (AMR) in cultured fishes is one of the major challenges faced in aquaculture. The high prevalence of bacterial infections in fishes leads to frequent use of antibiotics and thus their persistence in the aquatic environment, which in turn results in the proliferation of antibiotic resistant bacteria. The AMR in aquaculture can be transferred to clinically important strains of natural environment through horizontal gene transfer, thereby affecting the whole ecosystem. Most of the cultured fishes, including ornamental possess diverse pathogens exhibiting multiple antibiotic resistance. A thorough understanding of the gene transfer systems such as plasmids, transposons, integrons and gene cassettes can unravel the complexity of antimicrobial resistance in aquaculture. Continuous monitoring programmes, timely detections of the resistant bacteria and implementation of proper regulations are necessary to curb the dissemination of AMR in aquaculture. The present review summarises the antimicrobial use and AMR in cultured fishes, genetic mechanisms involved in the development of resistance, and the management strategies to restrict the spread of AMR in aquaculture.Department of Science and Technology (DST, SERB) for the Fellowship under National Postdoctoral Fellowship Scheme with Grant number PDF/2017/000378 and Director, National Bureau of Fish Genetic Resources and National Centre for Aquatic Animal Health, Cochin University of Science and Technology for the support

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In the fields of microbial, plant and animal sciencesAntimicrobial resistance is one of the major threats faced in aquaculture systems. Hence the present study is mainly focused on to determine the antimicrobial susceptibility associated with pathogens derived from diseased freshwater ornamental guppy fishes. Around fifteen isolates were resolved from the infected fishes and subjected to antimicrobial susceptibility testing, phenotypic and genotypic characterization. Disc diffusion method was adopted for checking the antibiotic susceptibility using 17 antibiotic discs belonging to different classes. Dendrogram generated 5 clusters based on the biochemical tests and representative isolates were sequenced and identified as Aeromonas hydrophila, Aeromonas sobria, Pseudomonas putida, Acinetobacter soli and Kurthia gibsonii. The Shannon wiener diversity index of the resolved isolates was found to be 1.395 as determined by Primer-E software. Among the isolates, the majority of them was found to be Pseudomonas putida and exhibited higher antibiotic resistance towards antibiotics of 10 classes including third generation Cephalosporin and others showed the same against antibiotics of at least 5 classes tested. All of the recovered isolates possessed the MAR index of greater than 0.2, indicating the heavier dose of antibiotics in the farm. The detection of plasmid-mediated class I integron in Aeromonas hydrophila, Aeromonas sobria and Acinetobacter soli indicated the possibility of heavier dissemination of antimicrobial resistant genes among the ornamental fishes. Gentamycin and Ciprofloxacin were significantly effective against all the isolates and can be successfully applied in aquaculture. The occurrence of antibiotic resistance reminds the proper surveillance and continuous monitoring programmes in the fish farms and usage of other effective alternatives.Department of Science and Technology (DST) for the Fellowship under National Postdoctoral Fellowship Scheme with Grant number PDF/2017/00037

Journal of Fish Diseases

Not AvailableMegalocytivirus cause diseases that have serious economic impacts on aquaculture, mainly in East and South-East Asia. Five primary genotypes are known: infectious spleen and kidney necrosis virus (ISKNV), red sea bream iridovirus (RSIV), turbot reddish body iridovirus (TRBIV), threespine stickleback iridovirus (TSIV) and scale drop disease virus (SDDV). ISKNV-mediated infectious spleen and kidney necrosis disease (ISKND) is a major viral disease in both freshwater and marine fish species. In this study, we report the isolation of ISKNV from diseased giant gourami, Osphronemus goramy, in India. Transmission electron microscopy of ultrathin sections of kidney and spleen revealed the presence of numerous polygonal naked viral particles having an outer nucleocapsid layer within the cytoplasm of enlarged cells (115-125 nm). Molecular and phylogenetic analyses confirmed the presence of ISKNV and the major capsid protein (MCP) (1,362 bp) gene in the infected fish had a high similarity to the other ISKNV-I isolates. Moreover, ISKNV was propagated in the Astronotus ocellatus fin (AOF) cell line and further confirmed genotypically. A high mortality rate (60%) was observed in gourami fish injected with ISKNV-positive tissue homogenate through challenge studies. Considering the lethal nature of ISKNV, the present study spotlights the implementation of stringent biosecurity practices for the proper control of the disease in the country