Model Systems of Human Intestinal Flora, to Set Acceptable Daily Intakes of Antimicrobial Residues

Abstract

The veterinary use of antimicrobial drugs in food producing animals may result in residues in food that might modify the consumer gut flora. This review compares three model systems that maintain a complex flora of human origin: (i) human flora-associated (HFA) continuous flow cultures in chemostats, (ii) HFA mice, and (iii) human volunteers. The ‘No Microbial Effect Level’ (NoMEL) of an antibiotic on human flora, measured in one of these models, is used to set the acceptable daily intake (ADI) for human consumers. Human volunteer trials are most relevant to set microbiological ADIs, and may be considered as the ‘gold standard’. However, human trials are very expensive and unethical. HFA chemostats are controlled systems, but tetracycline ADI calculated from a chemostat study is far above of that resulting from a human study. HFA mice studies are less expensive and better controlled than human trials. The tetracycline ADI derived from HFA mice studies is closer to the ADI obtained from studies with human volunteers. Keywords: ADI, animal model, antibiotic, gut flora, residues, resistance.