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We report the development of ddPCR assays for single and simultaneous detection of the bacterial pathogens Flavobacterium psychrophilum and Yersinia ruckeri in water from land-based recirculation aquaculture systems (RAS), producing Atlantic salmon (Salmo salar) smolt. The method was tested and verified for use in water analyses from RAS production sites, and proved to be specific and with sensitivity 0.0011 ng DNA for F. psychrophilum and 1.24 ng for Y. ruckeri. These bacteria are important fish pathogens that have caused reoccurring salmonid infection disease in RAS. Monitoring pathogen levels in water samples could be a useful alternative surveillance strategy to evaluate operational risk assessment connected to stress factors. Water quality is essential for fish health and growth in RAS production in general, and high or increasing levels of these pathogens in the RAS water may generate an early indication of unfavourable conditions in the RAS environment, and give directions to operational actions. This approach may reduce fish mortality, reduce production loss, and offer more effective and targeted preventive measures within RAS production., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

A new copper (I) complex, [Cu(NN 1 ) 2 ](ClO 4 ) , was synthesized, where NN 1 was a imine ligand 6-((quinolin-2-ylmethylene)amino)-2H-chromen-2-one obtained by a derivatization of natural compound coumarin. The structural characterization in solution was done by NMR techniques, UV-Vis and cyclic voltammetry. The potential antibacterial effect of [Cu(NN 1 ) 2 ](ClO 4 ) , was assessed for F. psychrophilum isolated 10094. F. psychrophilum is a Gram-negative bacterium which causes diseases such as bacterial cold-water disease and rainbow trout fry syndrome, causing large economic losses in the freshwater salmonid aquaculture industry. This complex show to have antibacterial activity against F. psychrophilum 10094 at non-cytotoxic concentration in cell line derived from trout ( F. psychrophilum 10094 IC 50 16.0 ± 0.9; RT-GUT IC 50 53.0 ± 3.1 µg/mL).

Turkey was the largest rainbow trout producer of the European countries in 2016, and the reason for this production is mainly attributed to its egg and fry production. Flavobacterium psychrophilum cause the highest rates of mortality in the starting to feeding stages of the fish. In the present study, twenty-five F. psychrophilum isolates recovered from rainbow trout, coruh trout and brook trout were analysed by RAPD-PCR, ERIC-PCR, REP-PCR and PCR-RFLP, including 16S rRNA, gyrA and gyrB gene regions and PCR-based serotyping method. The PCR-based molecular analysis showed that the isolates could not be differentiated exactly according to isolation source and geographical region. Most isolates were of type-1 and type-2, and some of them were of type-0 and type-3; in addition, one isolate showed a unique serotype. The combined analysis results showed that F. psychrophilum isolates discriminated as five different genotypes and all isolates were successfully discriminated based on host., (© 2018 John Wiley & Sons Ltd.)

Previously, rainbow trout fed deoxynivalenol (DON) or partially fed (pair‐fed) for 4 weeks before and during experimental infection with Flavobacterium psychrophilum had significantly decreased mortality rates. Similar results were obtained in the present study after 12 days, but not after 6 days, feeding 5 ppm DON or pair‐fed before infection. Furthermore, feeding 250 ppm chloroquine (CQ) also reduced mortality (p =.052) compared with controls and may have promise for treatment of some fish disease. Parallel groups of fish were maintained on the respective treatments for 15 days, with an additional group that was fasted, but were not infected to monitor autophagy. Fish that were fasted or fed DON had significantly increased LC3II in the liver and fasted fish had significantly decreased LC3II in muscle compared with controls using western blot. There was no difference in LC3II signal in the spleen of any treatment group. Fish that were fasted or pair‐fed had significant up‐regulation of the Atg genes atg4, atg7, lc3, gabarap and atg12 in muscle using quantitative PCR. Less alteration of Atg expression was seen in liver. Fish treated with CQ had significantly increased expression of atg4, becn1, lc3 and atg12 in the liver. Fish fed DON for 15 days had few alterations of Atg genes in either the liver or muscle. It is still not clear if autophagy is responsible for the resistance of rainbow trout fed DON, CQ or pair‐fed before F. psychrophilum infection. [ABSTRACT FROM AUTHOR]