Characterisation of lactic acid bacteria isolated from the hindgut of farmed Tasmanian Atlantic salmon (Salmo salar L.)

Between July 2011 and May 2012, 16 pooled faecal samples were collected on eight occasions (40 fish/ occasion) from Atlantic salmon fed two commercial diets in a farm in Tasmania, Australia. From a second Tasmanian farm, 12 pooled faecal samples were collected on three occasions (80 fish/ occasion) from salmon fed four trial diets. From these samples a total of 160 lactic acid bacteria (LAB) were isolated on MRS agar. Strains were initially typed using PhP-LB plates (PhPlate, AB) and divided into common types (CTs). Strains which belonged to the same CT and found on numerous sampling occasions (n = 73) were identified using 16S rRNA sequencing and tested for cytotoxins production, bacteriocins, adherence to Atlantic salmon kidney cells as well as competitively exclude 16 bacterial strains in vitro. These strains were also tested for their resistance against nine antibiotics commonly used in Aquaculture. The 73 LAB strains belonged to six species namely Enterococcus casseliflavus, E. faecalis, E. faecium, Pediococcus acidilactici, and Weisella hellenica of which, three different strains of W. hellenica and one P. acidilactici met most criteria including medium to high adherence and pathogen exclusion capability in vitro. The potential of these strains to serve as probiotic candidates is discussed.