identification of probiotic vibrios against pathogenic vibrios in rainbow trout

a total of 116 marine fishes and sediments were collected from persian gulf shore near bushehr in order to isolate vibrio species. after culturing on thiosulphate- cirate- bile salts- sucrose and with biochemical tests, 30 isolates showed vibrio characteristics which were categorized in 7 vibrio species, v. anguillarum, v. alginalyticus, v. harveyi, v. vulnfiicus, v. ordalii, v. carchariae and v. splendidus. in pathogenicity evaluation of vibrio isolates for rainbow trout(oncorhynchus mykiss, walbaum), v .vulnificus, v. angillarum and v. ordalii resembled the most pathogens. antigonistic effects of the isolates were determined using supernatant assay and double-agar layer method. three isolates, v. alginolyticus, v. splendidus and v. haveyi were separately incorporated into the feed and fed to rainbow trouts for 14 days at doses equivalent to 107-109 cells g-1 of feed and fish were challenged with pathogenic vibrios. whereas the untreated controls experienced survival rate of 46.6-53.3% when challenged by immersion with v. vulnificus v. anguillarum and v. ordalii, the probiotic treated groups remained healthy with a high survival rate of 93.3-96.6%. the probiotic vibrio species studied in this research reflected stimulation of innate immunity, namely enhanced phagocytic activity and phagocytic index of kidney macrophages  and respiratory burst activity of neutrophils.