Efficacy of oral streptomycin administration for the treatment of nocardiosis in the yellowtail Seriola quinqueradiata

The in vivo effects of streptomycin (SM) treatment for nocardiosis (caused by Nocardia seriolae) were examined in the yellowtail Seriola quinqueradiata by using artificial infection studies. By the immersion method, 44 yellowtails (mean weight = 66.8 g) were artificially infected with 1.0 x 10 5 cfu/ml of N. seriolae. After the infection was established, the fish were treated by oral SM administration at doses of 40, 80, and 160 mg/kg fish. The cumulative mortalities recorded in the control group (non-treated group) and those treated with 40, 80, and 160 mg/kg fish were 80.0%, 31.3%, 37.5%, and 6.3%, respectively. Significant differences (p < 0.05) were recorded between the control and SM-treated groups. Furthermore, the N. seriolae load decreased in the surviving fish in the SM-treated groups. In this study, we showed that SM can be used as a potential therapeutic agent for nocardiosis in yellowtail cultures.