Bacterial networks in Atlantic salmon with Piscirickettsiosis

Abstract

An unbalanced composition of gut microbiota in fish is hypothesized to play a role in promoting bacterial infections, but the synergistic or antagonistic interactions between bacterial groups in relation to fish health are not well understood. We report that pathogenic species in the Piscirickettsia, Aeromonas, Renibacterium and Tenacibaculum genera were all detected in the digesta and gut mucosa of healthy Atlantic salmon without clinical signs of disease. Although Piscirickettsia salmonis (and other pathogens) occurred in greater frequencies of fish with clinical Salmonid Rickettsial Septicemia (SRS), the relative abundance was about the same as that observed in healthy fish. Remarkably, the SRS-positive fish presented with a generalized mid-gut dysbiosis and positive growth associations between Piscirickettsiaceae and members of other taxonomic families containing known pathogens. The reconstruction of metabolic phenotypes based on the bacterial networks detected in the gut and mucosa indicated the synthesis of Gram-negative virulence factors such as colanic acid and O-antigen were over-represented in SRS positive fish. This evidence indicates that cooperative interactions between organisms of different taxonomic families within localized bacterial networks might promote an opportunity for P. salmonis to cause clinical SRS in the farm environment.

Oral administration of a new copper (I) complex with coumarin as ligand: modulation of the immune response and the composition of the intestinal microbiota in Onchorhynchus mykiss

“…Therefore, [Cu(NN 1 ) 2 ]ClO 4 administration could potentially help shift the microbiota composition towards that observed in salmonids ( Kim et al, 2021 ). An increase in Pseudomonas was identified in O. mykiss , which has been recognized as potential probiotics in fish ( Vidal et al, 2023 ), with higher abundance in specimens surviving infectious processes ( Valdés et al, 2020 ; Coca et al, 2023 ). On the other hand, the reduction in the production of butyric acid-producing bacteria (Clostridiales), acting as an immunomodulator, could partly explain the effect on stimulating the immune response towards an inflammatory state ( Vargas et al, 2023 ).…”

[Cu(NN1)2]ClO4, a Copper (I) Complex as an Antimicrobial Agent for the Treatment of Piscirickettsiosis in Atlantic Salmon

“…Finally, it was observed that the administration of the compound surprisingly increased the abundance of bacteria of the genus Piscirickettsia, to which P. salmonis belongs. However, it has been reported that this bacterium is part of the intestinal microbiota of healthy fish, and that an imbalance in the composition of the microbiota and the interaction between different metabolites of various bacteria generates the appearance of SRS [67]. These data are relevant when interpreting our results, because although the compound generated an increase in this bacterial genus, the administration of [Cu(NN 1 ) 2 ]ClO 4 during the challenge with P. salmonis generated protection, considerably increasing the survival of Atlantic salmon.…”