In vitro Studies of Amoxicillin on Antibacterial Activity for Some Fish Pathogens

Abstract

Minimal inhibitory concentration (MIC) of amoxicillin (AMPC) against Pateurella piscicida, Edwardsiella tarda, Aeromonas salmonicida, A.hydrophila, Vibrio anguillarum, and Streptococcus sp. were investigated. AMPC showed the highest antibacterial activity to P.piscicida. MICs of AMPC against 30 strains of P.piscicida isolated from cultured yellowtail (Seriola quinqueradiata) in 1985 were almost as high as that of ampicillin (ABPC), ranging from 0.025 to 0.1μg/ml. Furthermore, bactericidal activity of AMPC to P.piscicida was higher than that of ABPC. Sensitivity of P.piscicida, Streptococcus sp. or E.tarda to AMPC was kept almost the same level during the culture of 20 times transfer. These results suggest that AMPC can be applied for therapy of bacterial pseudotuberculosis of cultured yellowtail.