Antibacterial drugs have been widely used in animal and human medicine for more than 50 years, with significant benefits. However, use of antibacterial drugs in food-producing animals has given rise to concerns, particularly in regard to their potential impact on public health, arising from the emergence of resistant bacteria. Use of antibacterial drugs can contribute to the selection of resistant bacteria and their subsequent dissemination. Resistant bacteria of food-animal origin can be transmitted to humans via the food chain. Depending on the nature of the resistant phenotype, foodborne infections involving bacteria of animal origin expressing antibacterial resistance genes, could give rise to therapeutic failures. The nature of the resistance is important, as many of the antibacterial compounds used in the treatment of human infections, are also used to treat similar infections in animals. These include antimicrobial classes such as fluoroquinolones and the critically important third and fourth generation cephalosporins. When indicated, these classes of drugs are important for the treatment of bacterial infections associated with Salmonella species, Campylobacter species, and Escherichia coli. In addition to the emergence of resistant strains of bacteria, increasing use of these valuable therapeutic agents can increase the concentrations of drug residues in the food supply.
In this article, a review of antibacterial agents used in food-producing animals is presented. Selection of resistant bacteria following the use of antimicrobial agents is considered and the dissemination of these resistance markers is discussed. Finally the impact of resistant bacteria of animal origin and their residues on animal and public health is explored.