On July 6, 2012, the USDA Food Safety and Inspection Service (FSIS) announced the launch of new analytical methods and sampling procedures for the United States National Residue Program (NRP) for Meat, Poultry, and Egg products [Docket No. FSIS-2012-0012] (9 CFR Parts 417).
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Milk and other fluid samples such as urine collected from animals prior to slaughter could be used to assess if edible tissues are fit for human consumption if these assays are appropriately validated. Here, Sheila Tuftee from the ISU-VDL prepares samples for drug screening by LC-MS. As part of the restructuring process, the FSIS is implementing several multi-residue methods (MRM) for analyzing samples of meat, poultry, and egg products for animal drug residues, pesticides, and environmental contaminants in its inspector-generated testing program. The new MRM being implemented by the FSIS is reported to provide significant improvements to the previously imple mented testing strategy, including:
• It can screen for a variety of analytes, not just antibiotics.
• The method can be validated at levels appropriate in relation to tolerances.
• Because of the power of mass spectrometry, it can clearly distinguish individual analytes, even if multiple drugs are present in the same sample.
• Unknown microbial inhibition responses would be mitigated.
• The time and personnel needed to obtain results is reduced.
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There are 52 analytes appropriate for inclusion in the new MRM at and above the level specified (see Resources box). The MRM and the aminoglycoside method will replace the 7-plate bioassay and the KIS™ test as an initial screen test in the laboratory. The FSIS estimates a four-workday turnaround for negative samples and that that the new confirmation process for KIS-positive samples could take between three and 10 days, depending on the number of residues detected on any one sample, the number of tissues tested, and the type of confirmation or quantification required.
What motivated the changes?
The FSIS is making the changes to the NRP to:
• Identify emerging contaminants
• Prevent adulterated meat, poultry and eggs from entering the market place
• Discourage improper behavior by producers, processors and importers
• Close regulatory gaps between Agencies
What are the implications for bovine practitioners?
• The FSIS is now testing for prednisone, gamithromycin, sulfanilamide, sulfanitran, and beta-dexamethasone, which were not tested for previously. There is no tolerance established for many of these compounds that now are included in the test—most notably, dexamethasone. This raises significant questions about how the discovery of residues will be interpreted and enforced. It also gives practitioners the additional responsibility of ensuring that treated animals are free of any residues when consigned for human consumption. Sensitive and specific antemortem tests that correlate with tissue depletion profiles in cattle are needed to assist practitioners in making these decisions.
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