A rapid and efficient screening test is needed for the evaluation of antibiotic residues in catfish tissues. Procedures were developed to determine the optimum R processing of catfish tissues for use with the EZ Screen Test^R kit method. EZ Screen Test^R system is commercially available and approved for use in the detection of SDM in chicken products at the level of 0.1 ppm.

Catfish filet was spiked with sulfadimethoxine (SDM). Ten-fold and two-fold serial dilutions of samples were prepared to determine the sensitivity of the test. EZ Screen Test^R system detected SDM in catfish filet at the level of 0.1 ppm by the ten-fold dilution method. While using two-fold dilutions, EZ Screen Test^R system detected SDM level as low as 0.0125 ppm. In subsequent study, channel catfish were force-fed in a single or double dose of Romet 30^R comparable to 3% of their body weight for either 5 days or 10 days. Catfish filet were taken every day post-feeding for 14 days. There was no SDM detected at the level of 0.1 ppm in filet from any of SDM-treated groups at and after 5 days post-feeding. When data from EZ Screen^R. Test were compared to those from HPLC, EZ Screen Test^R had 100% sensitivity and 90% specificity. The results indicate that EZ Screen Test^R can be used to detect SDM residue in catfish fillet and may be applied to the field samples.