Experimental Treatment of Aeromonas salmonicida Infections with Enrofloxacin and Oxolinic Acid: Field Trails

Abstract

The antimicrobials enrofloxacin and oxolinic acid were evaluated under field conditions for treatment of clinical Aeromonas salmonicida infections in salmonids by feeding medicated diets. Treatment of Atlantic salmon Salmo salar with enrofloxacin or oxolinic acid at 5 mg/ kg per day for 5 d was not successful. Monitoring of enrofloxacin-medicated fish revealed low tissue and serum antimicrobial activities. Lack of efficacy in the Atlantic salmon trial may have been due to the low dose, lack of bioavailability of the drug, or lack of acceptance of the medicated ration. Treatment of hybrid brook trout Salvelinus fontinalis × lake trout S. namaycush was successful when enrofloxacin was used at 10 mg/kg per day for 10 d, but not when oxolinic acid was used at 5mg/kg per day for 10 d. Antimicrobial activity in tissues of enrofloxacin-medicated fish was elevated during the 10-d treatment period. No antimicrobial activity could be detected in muscle, skin, or liver of the enrofloxacin-medicated fish at 20 d after the last day of medication.