Adhesion to brown trout skin mucus, antagonism against cyst adhesion and pathogenicity to rainbow trout of some inhibitory bacteria against Saprolegnia parasitica 

Abstract

Biological control of saprolegniosis with bacteria might be an alternative to the use of chemical compounds. Among criteria for the selection of such bacteria are their absence of pathogenicity to fish and their ability to prevent adhesion of the pathogen to the skin mucus. The pathogenicity to rainbow trout of 21 bacterial isolates with in vitro inhibitory activity against Saprolegnia parasitica was studied. Fifteen of the isolates, identified as Aeromonas sobria, Pantoea agglomerans, Pseudomonas fluorescens, Serratia fonticola, Xanthomonas retroflexus and Yersinia kristensenii, were non-pathogenic when injected into rainbow trout. Their capacity to adhere to the skin mucus of male and female brown trout and to reduce the adhesion of S. parasitica cysts under exclusion, competition and displacement conditions was tested. The 15 bacterial isolates showed a low adhesion rate, ranging between 1.7% (for an A. sobria isolate) and 15.3% (a P. fluorescens isolate). This adhesion was greater in the case of mucus from male brown trout than from females. Similarities in the adhesion to male mucus and other substrates and correlation to that observed to polystyrene suggest that adhesion to skin mucus does not depend on the substrate. A high percentage (88.9%) of the S. parasitica cysts adhered to the skin mucus of male brown trout. Almost all of the bacteria reduced this adhesion ratio significantly under exclusion and competition conditions. However, only half of the isolates displaced cysts from skin mucus, and more bacterial cells were necessary for this effect. A novel method to study the adhesion of S. parasitica cysts to skin mucus of trout and their interactions with inhibitory bacteria is described. KEY WORDS: Saprolegniosis · Epidermal biota · Mucin · Binding ability · Salmo truttaResale or republication not permitted without written consent of the publisher

The development of the gut microbiota in rainbow trout (Oncorhynchus mykiss) is affected by first feeding and diet type

“…Worth considering for future studies would also be the route of probiotic administration. Recent studies have shown that alternative routes of administration of probionts like addition to the rearing water can protect rainbow trout from parasitic adhesion to the skin mucus (Carbajal-Gonzalez et al, 2013).…”

Biocontrol of saprolegniosis in rainbow trout (Oncorhynchus mykiss Walbaum) using two bacterial isolates (LE89 and LE141) of Pseudomonas fluorescens

“…In this respect, Nikoskelainen, Salminen, Bylund, and Ouwehand () have suggested that by adhering to and colonizing the intestinal mucosa, skin surface or gills, probiotics act against pathogens in various ways, blocking receptors, occupying space in the mucosa or competing for the nutrients present in the environment, thus giving rise to competitive exclusion. The capacity to grow in skin mucus is combined with a capacity to adhere to the same, although Carbajal‐González et al () found a low percentage of adhesion to male brown trout skin mucus: 2.9% in LE89 and 15.3% in LE141.…”

“…We used 15 bacterial isolates obtained from the skin of brown trout ( Salmo trutta L.) and rainbow trout ( Oncorhynchus mykiss Walbaum) that inhibit S. parasitica in vitro (Carbajal‐González et al, ; ) (Table ). All 15 bacteria were used to test saprolegniosis biocontrol through addition to water, and two of them, LE89 and LE141, through addition to feed.…”

“…Several in vitro studies have demonstrated that some bacteria inhibit Saprolegnia spp., including Pseudomonas fluorescens (Bly, Quiniou, Lawson, & Clem, ; Carbajal‐González, Fregeneda‐Grandes, González‐Palacios, & Aller‐Gancedo, ; Carbajal‐González, Fregeneda‐Grandes, Suárez‐Ramos, Rodríguez‐Cadenas, & Aller‐Gancedo, ; Hatai & Willoughby, ; Liu et al, ), Alteromonas sp. , Pseudomonas alcaligenes, Pseudomonas saccharophila, Aeromonas caviae and Aeromonas eucrenophila (Hussein & Hatai, ), Serratia marcescens (Zhang, Yang, Li, & Gao, ), Bacillus subtilis (Liu, Lu, Liu, & Zhou, ), Aeromonas media (Lategan & Gibson, ), Aeromonas sobria, Pantoea agglomerans, Serratia fonticola, Xhantomonas reflexus and Yersinia kristensenii (Carbajal‐González et al, ), Lactobacillus plantarum (Nurhajati, Atira, & Kadek Indah, ) and Pseudomonas aeruginosa (Moghaddam, Hajimoradloo, Ghiasi, & Ghorbani, ). However, their action in vivo has only been studied in eel Anguilla australis (Lategan et al ), silver perch Bidyanus bidyanus (Lategan et al ) and eggs of rainbow trout Oncorhynchus mykiss during incubation (Heikkinen et al, ).…”

“…In previous studies, our group identified several bacteria with the capacity in vitro to inhibit S. parasitica and analysed their adhesion to skin mucus, antagonism to S. parasitica cyst adhesion and lack of pathogenicity for rainbow trout ( Oncorhynchus mykiss Walbaum) (Carbajal‐González et al, ). The results suggested that some of these bacteria might prove useful in preventing saprolegniosis.…”