Romet® is an antimicrobial agent frequently used to treat enteric septicemia ofcatfish caused by Edwardsiella ictaluri and furunculosis in salmonid fishes caused by Aeromonas salmonicida. In recent years, Romet®-resistant bacterial strains of E. ictaluri and A. salmonicida have become more prevalent, rendering antimicrobial therapy with this agent useless. Furthermore, because ofthe development ofmultiple resistances, some bacterial strains may also be resistant to the only other approved and available agent, Terramycin®.