Tissue distribution of cefquinome after intramammary and “systemic” administration in the isolated perfused bovine udder

Mammary glands taken at slaughter from healthy lactating cows were perfused in vitro with warmed and gassed Tyrode solution. Cefquinome (88.8 mg cefquinome sulphate per 8 mL) was administered by the intramammary route to all quarters and/or “systemically” via the perfusion fluid at concentrations similar to those measured in plasma following intramuscular administration of 1 mg cefquinome per kg body weight. Samples of the perfusate were taken over a 6-h period and from the regional lymph nodes after 6 h. Using a scalpel, sections of glandular tissue – at different distances from and vertical to the teat right up to the udder base – were gathered from four quarters each per route of administration at 2, 4 and 6 h. The cefquinome content of the tissue samples was analysed by high performance liquid chromatography with diode array detection and of the perfusate samples by bioassay. intramammary administration, the concentration of cefquinome in the glandular tissue decreased exponentially with increasing distance from the teat. The addition of cefquinome to the perfusion fluid produced a mean concentration of 0.2–0.5 μg/g at all glandular tissue sites. Combined intramammary and systemic treatment ensured that concentrations exceeded the MIC90 values of the most common mastitis pathogens in all areas of the udder by 2 h post-administration. There was considerable variability in the tissue concentrations of cefquinome, particularly after intramammary administration. These results suggest that for the treatment of acute mastitis a combination of both intramammary and systemic administration is likely to be advantageous in order to rapidly produce maximum cefquinome concentrations in all regions of the udder.