Post Screening Methods for the Detection of Beta-lactam Residues in Pigs

Microbial growth inhibition assays are used to detect antimicrobial residues in meat. Postscreening methods may facilitate the selection of an appropriate chemical confirmatory method. Two such methods, the Charm II radioreceptor assay and High Voltage Electrophoresis (HVE), were evaluated for the detection of incurred β-lactam residues in pigmeat. Pig liver, kidney and muscle containing penicillin G, ampicillin, amoxycillin, cephalexin or ceftiofur was produced. In kidney, Charm detected residues of all 5 compounds in all of the replicates tested (90/90). HVE detected all of the amoxycillin and ampicillin replicates (18/18), 17/18 for Pen G, 14/18 for cephalexin and 7/18 for ceftiofur. In liver, Charm detected all of the cephalexin and ceftiofur replicates but only detected 3/9 pen G replicates and none of the amoxycillin or ampicillin replicates. HVE detected amoxycillin and ampicillin in 2/9 replicates, each of the cephalosporins in 1/9 replicates and did not detect pen G. In muscle, Charm detected 0, 9, 9, 3 and 5 replicates out of 27 for each of pen G, ampicillin, amoxycillin, cephalexin and ceftiofur. The equivalent detection for HVE was 4, 13, 15, 4 and 1. It is concluded that Charm is superior to HVE for cephalosporin detection. Both assays performed better with kidney than with either liver or muscle.