Chemical substances produced by microorganisms or synthetically that inhibit the growth of, or destroy, bacteria. Rules guiding the use of veterinary drugs and medicated animal feeds, including tolerance levels for drug residues in meats for human consumption, are set by the Center for Veterinary Medicine of the Food and Drug Administration (FDA). The Food Safety and Inspection Service (FSIS) enforces the FDA rules through a sampling and testing program that is part of its overall meat and poultry inspection program.