Application of granule and filament silver zeolite (Zeomic) in water filtration system for infection control of Streptococcus iniae in fry Rainbow trout

    Regarding the possibility of streptococcosis prevalence in Iran rainbow trout culture farming and great damage on the aquaculture industry, in this research, possibility of indirect use of silver zeolite as granule (100, 150 and 200 gr) and polyamide filaments (100 gr)  in water filtration of culture system of rainbow trout fry was studied to control Streptococcus iniae. After confidence of inhibitory power of silver zeolite against mentioned bacteria via in vitro experiments, minimum inhibitory concentration (MIC), zone of inhibition test and test tube test, the granular and filamentous filter media containing Zeomic was used in filters. In next stage, for in vivo experiments, S. iniae (10⁵ cell/ml) was inoculated to the water and efficacy of filters in inhibition of bacteria was evaluated by total count of bacteria (microbiological test), mortality rate, clinical signs and also kidney and spleen culture. Based on the results, the minimum inhibitory concentration of silver zeolite on the growth of S. iniae Aynyayy 250 µg/ml was calculated. The results indicated significant difference in decreasing of water bacteria, fish mortality and disease symptoms in treatments containing silver compounds compare to controls. In total, between tested filter media in this study, polyamide filaments containing silver zeolite have the highest efficacy for the use in water filtration system to control S. iniae with reduction of bacteria from 5.48 ± 0.01 log to 3.5 ± 0.17 log. According to the results, it seems that indirect use of studied silver compounds as filter application have the sufficient potential to control bacterial infection and disease prevention in culture system of rainbow trout. Other side effects of these materials on aquatic organism needs more research in future