Detecting Sulfamethazine Residues in Chicken Tissues Using the Delvotes^® SP System

Sulfamethazine-spiked chicken liver and kidney were tested for residues using the Delvotest SP. The results were compared to a standard plate assay using Bacillus subtilis as the test organism. The Delvotest SP gave positive responses to all homogenized liver replicates spiked with sulfamethazine at or above 1.0 μg/g of liver. Mixed responses were obtained at 0.5 μg/g and negative responses at ≤0.25 μg/g. The plate assay had a minimum sulfamethazine detection limit of 1 μg/g and 0.5 μg/g of liver and kidney, respectively. Chickens were dosed with sulfamethazine (100 mg/kg of body weight) daily for 5 days, and tissues were tested for residues after treatment stopped. The Delvotest SP was positive for all serum and kidney samples from the end of treatment to 24 h, and for muscle and liver samples up to 8 h. The plate assay detected the drug up to 24 h in serum and kidney samples and up to 8 h in liver and muscle samples. Kidney and serum samples both appeared to be good tissues for testing sulfamethazine residues in chickens. Serum could be used for antemortem screening, whereas kidney samples would appear to be the best for postmortem screening of residues in chickens.