Depletion study of trimethoprim and sulphadiazine in milk and its relationship with mastitis pathogenic bacteria strains minimum inhibitory concentrations (MICs) in dairy cows

Time-related concentrations in milk of a combination of trimethoprim-sulphadiazine (TMP-SDZ) intramammary formulated infusion and its relationship with pathogenic bacteria strains minimum inhibitory concentrations (MICs) isolated from clinical mastitis cows were analysed. The MICs study was performed for Escherichia coli, Staphylococcus aureus and Streptococcus sp. strains. The SDZ concentrations in milk were analysed using high-performance liquid chromatography (HPLC) and TMP using a microbiological assay. Ten lactating cows milked three times daily were used in the time-concentration studies of TMP-SDZ. Milk samples (approximately 20 mL) from the treated mammary quarters were taken at 6, 12, 24, 30 and 36 h after first administration. In order to define the withdrawal time, milk samples from the treated mammary quarters were taken at 24, 36, 48, 72, 84 and 96 h, after finishing the therapy. The MICs fluctuated between 1 and 8 microg/mL. Effective therapeutic concentrations lasted for 36 h when intramammary infusion was repeated three times every 12 h. No TMP was detected in milk for 24 h after finishing therapy. Milk SDZ concentrations were below 0.1 microg/mL in all treated cows after 84 h finishing therapy. At 96 h after finishing therapy, no SDZ milk concentrations were found in six animals, although four animals of the experimental group still had concentrations of 0.07 microg/mL.

Absorption and excretion of cefquinome in coho salmon (Oncorhynchus kisutch) in freshwater at 10 degrees C

The absorption and elimination of cefquinome in serum and tissues of coho salmon were studied. The study was performed in freshwater at 10 degrees C with fish weighing 100 +/- 5 g (mean and standard deviation). Single doses of 5, 10 and 20 mg/kg were administered intraperitoneally to 30 fish for each dose. The maximum concentration occurred in the following order; kidney and liver > serum > muscle > brain. The pharmacokinetic analysis and predictive withdrawal times were calculated using only the dose of 20 mg/kg body weight. The peak cefquinome concentrations (Cmax) in serum (3.35 +/- 0.45 micrograms/ml) and muscle (2.87 +/- 0.53 micrograms/g) were achieved at 12 h. In the brain, the Cmax was 2.18 micrograms/g at 6 h. The half-lives (t1/2) in serum, muscle, brain, liver and kidney were 20.56, 8.93, 9.35, 113.61 and 119.48 h, respectively. With the detection limit of 0.015 microgram/g for the cefquinome, the predicted withdrawal time with 95% confidence for muscle tissue was 104.2 h at 10 degrees C for the 20 mg/kg dose. The results suggest that cefquinome could be efficacious and safe for the consumer in treating bacterial diseases of coho salmon in fresh water. Nevertheless, future studies are required in order to determine an adequate dose with the corresponding withdrawal times.