Bacteria in the gut of juvenile cod Gadus morhua fed live feed enriched with four different commercial diets

Abstract

Atlantic cod, Gadus morhua L., larvae were fed rotifers, Brachionus plicatilis and Artemia franciscana enriched on four different commercial media, using the manufacturers' protocols. Pooled samples of 20 cod larvae were homogenized, diluted, and plated out on Petri dishes. The number of colony-forming units per larva was estimated, and the dominant strains subsequently sampled for sequencing of 16S rDNA. Bacteria showing high sequence similarity to a pathogen characteristic of cod and other fish species, Listonella anguillarum, were present in all four groups. Other taxa present among the dominating bacterial colonies were Pseudoalteromonas sp., and Vibrio sp. However, these bacteria could be assigned to genera only. The different enrichments probably affected the number of colony-forming bacteria per millilitre in the enrichment cultures as well as in the larval gastrointestinal (GI) tract. Also, the composition of the microbiota associated with the larval GI tract was probably affected by the enrichment media.

Microbial diversity of intestinal contents and mucus in yellow catfish (Pelteobagrus fulvidraco)

“…Some certain strains of these bacteria possess the virulence factors necessary to induce disease (Cahill, 1990). Vibrio species have previously been detected in gut of a wide variety of fishes, such as halibut larvae (Verner-Jeffreys et al, 2003;Jensen et al, 2004), hybrid tilapia (Oreochromis niloticus) (Al-Harbi and Uddin, 2004), Atlantic cod (Gadus morhua) (Korsnes et al, 2006;Ringø et al, 2006), Atlantic salmon (Salmo salar) (Hovda et al, 2007) and so on, and the importance of the genera Vibrio in aquaculture have been discussed (Thompson et al, 2004;Austin, 2006). Shewanella putrefaciens is a potential pathogen of fish, and has been isolated from the intestine of rainbow trout (Oncorhynchus mykiss) (Huber et al, 2004;Koziñska and Pêkala, 2004;Pond et al, 2006).…”

Screening and characterisation of potentially pathogenic bacteria associated with Atlantic codGadus morhualarvae: bath challenge trials using a multidish system

“…In intensive aquaculture, cod larvae are offered rotifers, usually Brachionus plicatilis, and brine shrimp, mostly Artemia franciscana, as live feed (Svåsand et al 2004, Reitan 2005. Recently, Korsnes et al (2006) demonstrated the presence of bacteria with high sequence similarity to Vibrio anguillarum in rotifer cultures and the gut of cod larvae fed rotifers. Both rotifers and Artemia sp.…”

“…High larval densities and suboptimal rearing conditions may provide a good environment for opportunistic bacterial pathogens to flourish (Vadstein et al 2004), and high rates of mortality are still common. Commercial enrichment diets for rotifers may enhance the growth of pathogens including Vibrio anguillarum (Korsnes et al 2006). Adult cod are frequently subject to classical vibriosis caused by V. anguillarum (reviewed by Samuelsen et al 2006).…”

“…During first feeding, yolk-sac larvae in general are subject to a massive inflow of bacteria from the live feed organisms Brachionus plicatilis and Artemia spp., resulting in a shift in intestinal bacterial flora (Brunvold et al 2007), and suspected pathogens such as V. anguillarum may accumulate in the live feed (Korsnes et al 2006). The mucosal surfaces of fish serve as a substrate for bacterial adhesion (Spangaard et al 2000) and thereby a potential portal of entry.…”

Viral and bacterial diseases of Atlantic cod Gadus morhua, their prophylaxis and treatment: a review

“…During first feeding, yolk-sac larvae in general are subject to a massive inflow of bacteria from the live feed organisms Brachionus plicatilis and Artemia spp., and suspected pathogens, like Listonella anguillarum, may be accumulated in the live feed (Korsnes et al 2006). The mucosal surfaces of fish serve as a substrate for bacterial adhesion (Hansen & Olafsen 1989).…”