A Microbial Assay System for the Confirmation of Results of Receptor Assays for Antibiotic Residues in Milk1

Abstract

A microbial assay system has been devised as a unified confirmation procedure for antibiotic residues found in milk using the Charm II receptor assay. Chlortetracycline, streptomycin, erythromycin, penicillin and chloramphenicol residues are assayed using three organisms and five types of agar. Assay specificity is achieved by making use of the differences in the antibiotics' activity at selected pH's and differences in stability with regard to enzymes and temperatures, as well as differences in the sensitivity of the organisms to different antibiotics. The system has the flexibility to be used piecemeal when only one or two residues require confirmation, or in its entirety when confirmation of multiple residues is needed.