ESTABLISHMENT OF A MICROBIOLOGICALLY ACCEPTABLE DAILY INTAKE OF ANTIMICROBIAL DRUG RESIDUES

A model is presented to calculate the microbiologically acceptable dai ly intake (ADI(m)) of antibiotic residues in food products. The ADI(m) calculation is based on MIC values for indicator bacteria Escherichia coli, Bacteroides fragilis, Bifidobacterium spp. and Eubacterium spp. , established under gut-like conditions in an in vitro simulation mode l. The maximum residue level (MRL) for residues in food products can b e derived from the ADI(m). Four phases can be distinguished in this ga stro-intestinal simulation model, namely: 1. In vitro determination of the MIC for each bacterial strain by a standard method. 2. Incorporat ion of the drug into food (meat, milk) followed by testing of the stab ility of the antibiotic under out-like conditions. 3. Adjustment of th e 'gastric' fluid to the duodenal situation, inoculation with the test bacteria and anaerobic incubation at 37 degrees C for at least 18 h. 4. MIC reading confirmed by counting bacteria growing on specific soli dified media. In this study the method for calculation of ADI(m) and M RL is given for flumequine as model drug. On the basis of MIC(50) Valu es for E. coli strains, a MRL for flumequine of 1.0 mu g/g meat or 0.2 5 mu g/ml milk was calculated. It is suggested that, depending on the antibacterial spectrum of the antibiotic involved, the ADI(m) can be d etermined with selected indicator bacteria, incubated under simulated gastrointestinal conditions.