Immunochemical detection of antibiotics and sulfonamides

To control the maximum residue limits (MRLs) for residues of veterinary drugs in food of animal origin, according to EU regulations, a broad spectrum of sensitive analytical methods is required. One effective approach is the development of immunoassays, particularly for screening purposes. Strategies for the production of specific polyclonal and monoclonal antibodies against beta-lactams, tetracyclines, streptomycin, chloramphenicol, sulfonamides and trimethoprim, are outlined, as well as methods for the synthesis of the respective enzyme-labelled antigens. The sensitivity and the specificity of the antibodies were characterized, and the immunochemical test systems were designed as quantitative routine tests (microtitre plate format) and as rapid qualitative tests (membrane-based assay formats). The detection limits of the assays were found to be well below the regulatory limits. The range of recovery, for the analysis of artificially contaminated samples, was between 68 and 104%. In principle, the enzyme immunoassays for antimicrobial drugs showed the advantage of sensitivity and speed together with the simplicity of manipulations involved in the procedure. However, because of the results of the specificity studies, as well as the possibility of false positive results owing to unspecific inhibition of the assay, confirmation of immunoassay results is still required for all legal and statutory purposes.