Stimulated Growth and Innate Immunity in Brook Charr (Salvelinus fontinalis) Treated with a General Probiotic (Bactocell®) and Two Endogenous Probiotics That Inhibit Aeromonas salmonicida In Vitro

Abstract

Aeromonas salmonicida subsp. salmonicida is a Gram-negative bacterium causing furunculosis, an opportunistic infection of farmed salmonid fish. Current treatment methods against furunculosis rely heavily on antibiotherapy. However, strains of this opportunistic fish pathogen were found to possess genes that confer resistance to major antibiotics including those used to cure furunculosis. Therefore, dispensing bacterial symbionts as probiotics to susceptible hosts appears to be a promising alternative. Here, we present the genomic characterization and in vivo safety assessment of two brook charr (Salvelinus fontinalis) bacterial symbionts that inhibited A. salmonicida subsp. salmonicida growth in vitro (Pseudomonas fluorescens ML11A and Aeromonas sobria TM18) as well as a commercialized probiotic, Pediococcus acidilactici MA18/5M (Bactocell®). The genomic sequences of ML11A and TM18 obtained by whole-genome shotgun sequencing lack key virulence factor genes found in related pathogenic strains. Their genomic sequences are also devoid of genes involved in the inactivation (or target modification of) several key antimicrobial compounds used in salmonid aquaculture. Finally, when administered daily to live brook charr fingerlings, ML11A, TM18 and Bactocell® helped improve several physiological condition metrics such as mean body weight, Fulton’s condition factor and blood plasma lysozyme activity (an indicator for innate immune activity).

Dietary Supplementation of a Commercial Prebiotic, Probiotic and Their Combination Affected Growth Performance and Transient Intestinal Microbiota of Red Drum (Sciaenops ocellatus L.)

“…Interestingly, improved weight gain was only observed for red drum fed diets supplemented with Bactocell ® . This finding is corroborated by studies that also reported a superior growth performance of other cultured fish fed the same probiotic supplement, such as the Brook charr ( Salvelinus fontinalis ) [ 27 ], zebrafish ( Danio rerio ) [ 28 ], and Asian sea bass ( Lates calcarifer ) [ 29 ]. Contrasting with the present study, an improved weight gain was promoted by the interaction between Bactocell ® and assorted prebiotic compounds in Nile tilapia ( Oreochromis niloticus ) [ 30 ], Korean rockfish ( Sebastes schlegeli ) [ 31 ], Asian sea bass [ 29 ], and European sea bass ( Dicentrarchus labrax ) [ 32 ].…”

Editorial for the Special Issue: Gut Microorganisms of Aquatic Animals

“…Moreover, as we get a sharper insight on these associations, symbiotic microbes can reciprocally interact with the aquatic environment even at the ecosystem level [2,3]. The articles published in the special issue “Gut Microorganisms of Aquatic Animals” are a contribution towards the scientific efforts to unravel some of the associations between freshwater [4], ornamental [5] and marine [6,7,8] fish, as well as shrimp [9,10,11] and their microbes. These papers cover multiple issues on aquatic animal–microbe interactions: healthy or diseased fish, the impact of pollution and handling practices on fish gut microbiota, and the effect of probiotics in the gut.…”