THE USE OF MICROBIOLOGICAL END-POINTS IN THE SAFETY EVALUATION AND ELABORATION OF MAXIMUM RESIDUE LIMITS FOR VETERINARY DRUGS INTENDED FOR USE IN FOOD-PRODUCING ANIMALS

The safety evaluation of veterinary drugs intended for use in food pro ducing animals relies heavily on the results of toxicity studies in la boratory animals, supported where possible by any data resulting from human exposure. The general approach involves the calculation of an ac ceptable daily intake which in turn can be used to elaborate maximum r esidue limits. It is an approach used in the European Union, in other countries and at the international level. In recent years, concern has been expressed over the presence of microbiologically active residues of veterinary drugs in food and their possible effects on the human g astrointestinal microflora. Methodologies for conducting microbiologic al safety studies have been investigated and approaches to microbiolog ical safety assessments have been debated. The whole approach has prov ed to be controversial, partly because there are considerable doubts o ver the ability of low concentrations of antibiotic substances to prod uce adverse effects on the human gut flora and partly because there ar e no validated methods for testing for these attributes. This paper re views the problems in some detail and discusses the regulatory consequ ences.