Abstract
Application of erythromycin (EM) to spontaneous streptococcal infections in cultured yellowtails, Seriola quinqueradiata, were reviewed.
In vitro, EM was active against a wide range of bacteria pathogenic for fish. Stock strains and fresh field isolates of Streptococcus sp. were susceptible to EM whose MIC values varied from 0.05 to 0.2μg/ml. There were no resistant streptococcal strains so far tested. The MIC of EM was slightly affected by inoculum size and medium pH.
In vivo, orally administered EM was effective against experimental infections with Streptococcus sp. in yellowtails. It was easily absorbed by oral administration and distributed to blood and tissues including brain within 1 h after administration. Peak levels were usually attained 1 to 3 h postadministration. Acute toxicity of EM was low in yellowtails, its LD50 value being more than 2, 000mg/kg. Abnormality possibly caused by EM was not found in yellowtails receiving the repeated doses of the drug at a dose of 100 mg/kg/day for 10 days.
In the clinical studies, EM was effective against streptococcal infections in cultured yellowtails at doses of 25-50 mg/kg/day for 4-7 days.
