The in vivo efficacy of the Aryl-fluoroquinolone, A-56620, was determined by bacterial challenge of channel catfish. Fish were immersed for 30 seconds in Brain-Heart Infusion broth previously inoculated with Edwardsiella ictaluri. A prepared diet that supplied 12.5, 25.0 or 50.0 mg of active drug/kg of body weight was fed to fish. A significant reduction in mortality (p =.038) was noted between all medicated treatments and unmedicated controls.

Additional studies have been performed to determine the most effective dosage and duration of treatment. Fish exposed to Edwardsiella ictaluri were fed diets that supplied 0.0, 2.0, 6.0, 10.0 and 14.0 mg drug/kg body weight, along with two treatment periods (5 days and 10 days). Results of these trials will be discussed.