Laboratory Efficacy of Enrofloxacin for the Control ofAeromonas salmonicidaInfection in Rainbow Trout

Efficacy of enrofloxacin (Baytril®: Bayer Co.) was evaluated in the laboratory for control of Aeromonas salmonicida infection in rainbow trout Oncorhynchus mykiss. Minimuminhibitory-concentration studies of enrofloxacin used against several A. salmonicida isolates indicated efficacy at concentrations below 0.125 μg/mL. In laboratory studies in which rainbow trout were challenged with A. salmonicida, a reduction in percent mortality was observed among fish receiving enrofloxacin (in feed) at rates of 1.25–2.5 mg/kg fish daily for 10 d when compared with mortality of nonmedicated controls.