Tissue distribution of marbofloxacin after ‘systemic’ administration into the isolated perfused bovine udder

Mammary glands taken at slaughter from healthy lactating cows were perfused in vitro with warmed and gassed Tyrode solution. Marbofloxacin was administered “systemically” via the perfusion fluid at concentrations similar to those measured in plasma following intravenous administration of 2 mg/kg marbofloxacin. Samples from the perfusate were taken over a 24 h period. Glandular tissue samples at different vertical distances from the teat up to the udder base were gathered from each of the four quarters after 3, 6, 12 and 24 h. The marbofloxacin content of the tissue samples was analysed by high performance liquid chromatography with UV detection.The addition of marbofloxacin to the perfusion fluid produced median concentrations above the MIC90 (0.016 μg/mL) against Escherichia coli at all glandular tissue sites measured after 3 and 6 h with remarkable variations. Samples taken after 12 and 24 h contained marbofloxacin in concentrations (median) of 0.22 (<0.05–0.32) μg/g and 0.13 (<0.05–0.16) μg/g. It is concluded that a systemic administration of marbofloxacin is well suited for the treatment of E. coli mastitis.