Bath treatment, an alternative method for the administration of the quinolones flumequine and oxolinic acid to halibut Hippoglossus hippoglossus, and in vitro antibacterial activity of the drugs against some Vibrio sp

Administration of flumequine and oxolinic acid to halibut Hippoglossus hippoglossus by bath resulted in significant tissue levels of both the antibactenals. Bath treatment using 150 mg 1-' of flumequine and 200 mg 1-' of oxolinic acid for 72 h resulted in flunlequine concentrations of 14.2 pg g-' in muscle and 85.4 pg g-' in abdominal organ homogenate and oxolinic acid concentrations of 9.4 pg g-' in muscle and 72.6 pg g-' in abdominal organ homogenate. Excretion of both antibacterials was rapid and characterised by elunination half-lives (t1,2) of 10 and 15.6 h respectively for flumequine and oxolinic acid In muscle and 9.8 and 15.0 h respectively in the abdominal organ homogenate. The corresponding elimination times (E,) were 6.5 and 8 d respectively for flumequine and oxolinic acid in muscle and 7.5 and 9 d respectively in abdominal organ homogenate when a maximum residue concentration of 0.05 pg g-' was applied for both drugs. The minimum inhibitory concentration (MIC) against strains of Vibrio sp. ranged from 0.015 to 1.0 pg m]-' for flurnequine and 0.015 to 0.5 pg ml-' for oxolinic acid. Following bath treatment, tissue levels of flumequine and oxolinic acid greater than MIC for susceptible strains (<0.0625 pg rnl-') were maintained for up to 6.5 and 8 d respectively for flumequine and oxolinic acid in muscle and 7.5 and 9 d respectively in abdominal organ homogenate.