An on-farm method for determination of sulfonamide drug residues in turkeys. 1. An agar-diffusion analysis for sulfadimethoxine in whole blood.

A simple and inexpensive sulfonamide-screening test was evaluated using turkeys. An agar-diffusion procedure was developed to estimate the levels of sulfonamides in the edible tissues of turkeys by determining the drug level in whole blood. The analysis was adapted for use on whole blood that was easily collected from live birds on the farm with minimal equipment and skill. This Whole Blood Sulfa Test (WBST) was quantified by the use of a standard curve and was successfully applied to on-farm use in the Pacific Northwest. Agar plates were prepared using fortified Mueller-Hinton medium. Bacillus megaterium spores were applied to the agar to form confluent growth, and paper discs (10 mm) were laid onto the agar. Whole blood was collected from commercial turkeys prior to marketing, and the blood was immediately applied to the test paper discs. After incubation, blood that contained sulfa inhibited bacterial growth around the disc, and the clear zones of inhibition were measured. The WBST was consistently accurate to 1.22 ppm, and sulfa levels were detected as low as .04 ppm. Results were attained in 12 hr and were relatively inexpensive at $3.00/test/flock.