January 31, 2022

Food Safety & Drug Residues Kits

By Marcia Ray

Drug Residues and Microbial Contamination in Food: Surveillance and Compliance

A primary goal of US food safety programs is the control of contaminants that may appear in food due to drug use in animals or the inadvertent introduction of microorganisms. Drug residue control and surveillance for microbial contamination are achieved through an extensive and rigorous process of sampling, testing, reporting and compliance. Tens of thousands of samples are collected and processed annually in routine screening procedures intended to statistically identify the presence of residues and microorganisms.

Three agencies do most of the work to protect the public from residues and microbial hazards: the U.S. Department of Agriculture (USDA), including the Food Safety & Drug Residues Kits Inspection Service (FSIS), and the Agricultural Marketing Service. (AMS); the Food and Drug Administration (FDA); and the United States Environmental Protection Agency (EPA).

The USDA is responsible for enforcing the Federal Meat Inspection Act (FMIA), the Poultry Products Inspection Act (PPIA), and the Egg Products Inspection Act (EPIA). Within the USDA, FSIS is responsible for the wholesomeness and safety of fresh meat, poultry, and processed meat and poultry products intended for human consumption. Inspects slaughter and processing establishments and samples and analyzes tissues derived from livestock and poultry at or after slaughter.

Inspection and testing are intended to ensure, among other things, that meat and poultry do not contain residues of drugs, pesticides, or pathogens that cause adulteration as defined in the FMIA or PPIA. When residue violations are detected, FSIS notifies FDA, as FDA is authorized to take legal action against violators. AMS is responsible for the wholesomeness and safety of egg products. Performs inspections and analyzes samples of chemical residues to ensure compliance with EPIA in plants that process egg products.

The FDA enforces the Federal Food, Drug, and Cosmetic Act (FDCA). The FDA is directly responsible for ensuring the safety of milk and shellfish for human consumption and that animal feed is safe and free of illegal drug residues, pesticides, or other environmental contaminants. The FDA also approves drugs used for food-producing animals, establishes safety and tolerance levels for animal drugs, and sets action levels for unavoidable environmental contaminants that could adulterate food. (The section on “Food Residue Tracking: Regulatory Information” describes tolerance, safety, and activity levels.)

EPA is responsible for administering and enforcing the Federal Insecticide, Fungicide, and Rodenticide Act, which regulates the manufacture, sale, and use of pesticides. EPA is also responsible under the FDCA for establishing tolerance levels and recommending action levels to FDA and FSIS for residues of pesticides in food. Under the Toxic Substances Control Act, the EPA also regulates other chemicals (such as industrial chemicals) that can adulterate food.

Monitoring Of Drug Residues In Food

Researchers can use sophisticated chemical detection methods or radioactively labelled drugs to study the pharmacokinetics, tissue distribution, and metabolism of a test drug or compound and establish the total residue content of the drug present in edible tissues and tissues. specific to the test site of treated animals. Muscle, liver, kidney, and fat are typically tested because these are the tissues that are normally ingested in large amounts, tissues that function as storage sites for fat-soluble residues, or tissues that metabolize most of the drug in the process. body elimination.

Drug residue levels in milk and eggs are determined where appropriate. The metabolic profile of the test compound is determined in a sample of each representative edible animal tissue and in animal fluids such as urine or milk, where appropriate. Urinary and faecal drug excretion patterns are useful in determining the biochemical events that regulate drug elimination from the body. For example, biochemical events in the liver and kidney increase the aqueous solubility of compounds that are otherwise poorly soluble in water by adding glucuronide or sulfate moieties.

Most drugs are metabolized and broken down into inert forms or metabolically conjugated with anions such as sulfate or glucuronide in the liver or kidney. Another use of metabolization and elimination data is to help establish withdrawal times for drugs used in animals intended for human consumption. The task of tracking drug residues would be considerably more complicated if all-important animal tissues had to be tested for residues. To facilitate inspection and detection of carcass or product, regulatory agencies have determined that a single tissue site should be selected for routine residue monitoring.

Based on pharmacokinetic, drug distribution, and accumulation-depletion data, the target tissue is one from which residues are depleted at the slowest rate. In the target tissue, the parent drug or a metabolite is selected as a marker residue. A tolerance level for the marker residue is then determined. The tolerance level is the concentration of the marker residue in the target tissue when all residues in all edible tissues are at or below what is considered the safe concentration for that drug.

This amount or concentration is derived from an acceptable set of toxicology, metabolism, and residue studies conducted by a pharmaceutical company that has submitted that data as part of a New Animal Drug Application (NADA). A tolerance level for drug residues in meat, milk, and eggs from food-producing animals is also the amount that is formally established and published at the time of drug approval by the FDA. the CVM. The tolerance level is established to facilitate the control of drug residues entering the food chain and to further assist in the regulation of animal drug use.

Unresolved Dairy Testing Issues

There is concern within the dairy industry that tests for antibiotics in milk are sensitive but are largely confounded by variable specificity. As such, Cullor (1992) and Cullor et al. (1994) considered the consequences of false-positive test kit results and summarized the following:

  • False-positive results from the test kit can lead to unwarranted milk wastage and huge financial loss. (Note: The committee was unable to find data on the rate of true false-positive tests or data on the amount of milk that was discarded due to false-positive test results.)
  • The dairy industry may be harmed if antibiotic tests that do not adequately identify untreated cows are used indiscriminately to test samples from individual cows. False-positive results create mistrust among consumers, producers, veterinarians, and regulatory personnel because they are interpreted to mean that bulk tank milk is not adequately controlled for safety.
  • False-positive residue results may lead to the inaccurate conclusion that substantial proportions of dairy cows release residues into the milk supply every day.
  • Despite the efforts of the dairy industry to produce a safe and wholesome product, the widely publicized reports of residues in milk, which are based on inappropriately applied and validated technologies, will be the reports that the milk consuming public will remember and answer to.
  • Excessive positive test results, after recommended withdrawal times have been followed, will result in individual dairy cows being removed from the production line. In the worst case, false-positive test results could result in cows being euthanized for economic reasons.
  • Eventually, this issue will harm international trade due to the belief that too many antibiotics are being fed to animals that are not detected by the bulk tank monitoring system on dairy farms or meat processing plants.