Evaluation and Testing of Charm Test II Receptor Assays for the Detection of Antimicrobial Residues in Meat

Abstract

Charm Test II receptor assays for β-lactams, sulfonamides, streptomycin and erythromycin were tested with standard solutions of targeted antimicrobials and with fortified kidney, liver and muscle samples. The degree of response obtained with the β-lactam assay varied among equimolar amounts of 8 β-lactams. The sulfa assay was positive, with varying response, to equimolar amounts of four different sulfonamides and negative for trimethoprim. The streptomycin assay also detected dihydrostreptomycin, but was negative for gentamicin and neomycin. The erythromycin assay was negative for oleandomycin but positive for tilmicosin and tylosin. No evidence of cross reactivity was detected among the compounds targeted by the four assays.

These assays were then used to analyze samples of kidney from 264 cull Holstein cows that were slaughtered at a local packing plant. Liver and diaphragm muscle tissue from carcasses having positive kidney results were also tested. Kidneys from 12 cows were positive for streptomycin by the Charm Test II. Four livers and one diaphragm muscle from the same 12 cows were also positive. The kidneys and livers from four cows and the diaphragm muscle from three cows were positive by the Charm Test II for p-lactams. Penicillin G was confirmed by high performance liquid chromatography (HPLC) in three of these kidney-liver pairs and in two of the associated diaphragm muscles. Tissues from one cow tested positive for sulfonamides, with sulfamethazine confirmed in liver, kidney and diaphragm muscle by thin layer chromatography. All kidneys tested negative using the erythromycin test.