Abstract
Anti-bacterial activity of six approved drugs for ayu Plecoglossus altivelis, i.e. florfenicol (FFC), oxolinic acid (OXA), sulfisozole sodium (SIZ), sulfamonomethoxine, ormetoprim (OMP) and sulfamonomethoxine-ormetoprim combination, was examined against four Edwardsiella ictaluri strains. Of these drugs, FFC, OXA and OMP inhibited bacterial growth with MIC lower than 1 μg/mL. When chemotherapeutic efficacy of FFC, OXA and SIZ was examined against experimentally E. ictaluri-infected ayu, FFC and OXA strongly reduced mortality of fish. Although SIZ was slightly effective, survivors from the SIZ-treated group showed high carrier rates for E. ictaluri, suggesting that FFC and OXA are candidates in treating E. ictaluri infection of ayu.
