Antimicrobial residues methods

Under the pressure of an increasing number of drugs with fixed tolerance or maximum residue limits (MRLs), demands on methods to detect antimicrobial residues in edible animal products have changed markedly during recent decades (1). To satisfy these demands and prevent contaminated products from entering the food chain, many microbiological tests with sufficient detection sensitivity of as many analytes as possible in animal tissues, milk, eggs, honey, and fish have been developed or modified. 

In summary, MIAs are the methods of choice when a cost-effective qualitative measure of the biological activity associated with unknown antimicrobial residues is required. When samples are received for analysis at a control laboratory or at a farm/abattoir site, there may be very limited (if any) information concerning what antimicrobial compounds the animal was treated with therefore, the use of multi-residue broad-spectrum MIAs can rapidly and efficiently identify the presence of many of the commonly used compounds. At the present time, a selection of commercial kits is available in the form of tube diffusion assays, disk diffusion assays, and swab devices. 

Pikkemaat MG, Oostra-van Dijk S, Schouten J, Rapahini M, van Egmond HJ, A new microbial screening method for the detection of antimicrobial residues in slaughter animals The Nouws antibiotic test (NAT-screening), Food Control 2007 19 781-789. 

Microbiology Laboratory Guidebook, Method 34.02, Bioassay for the Detection, Identification and Quantitation of Antimicrobial Residues in Meat and Poultry Tissue, US Dept. Agriculture, Food Safety and Inspection Service (available at http //WWW. fsis.usda.gov/PDF/MLG 34 02. pdf accessed 11/01/10). 

Langeveld PC, Stark J, Van Paridon PA, Method for the Detection of Antimicrobial Residues in Food and Bodily Fluid Samples, US Patent 7,462,464, 2008. 

Berardi G, Bogialli S, Curini R, et ah. Evaluation of a method for assaying sulfonamide antimicrobial residues in cheese Hot water extraction and liquid chromatography-tandem mass spectrometry, J. Agric. Food Chem. 2006 54 4537-4543. 

Confirmation of quantity may also require the use of the method of standard addition or the inclusion of isotopi-cally labeled standards, although there are currently few such materials available for antimicrobial drugs, as noted in a review in 2009. Some examples of the application of isotopically labeled internal standards to methods for antimicrobial residues include the determination of chloramphenicol in meat, fish, and other biological matrices nitrofuran residues in milk and nitroimidazole residues in eggs and animal plasma. ... 

For example, using this approach a method to test for an antimicrobial residue with a MRL of 100.0 p-g/kg would have an estimated expanded uncertainty of ... 

Cold-pressed essential oils from the peel are some of the most important by-products recovered during the processing of Citrus fruits. The presence of limonene in the aqueous discharges, with its antimicrobial activity [1], decreases the effectiveness of the waste treatment system and increases the time necessary for the biological breakdown of the organic matter produced in the peel oil recovery system [2,3]. Additional recovery of essential oils from waste water would increase industry s returns and reduce the pollution problems associated with the disposal of waste water [4,5]. Several methods for reducing the levels of residual essential oils in the aqueous effluent have been developed over the years [6-11]. 

A variety of methods were developed for the identification and determination of the antimicrobial nitrofurans. They include LC, colorimetric and polarographic methods. Nitrofurans could be determined in animal tissues by extraction with acetonitrile, SPE and LC-UVD533. An LC-UVD method was statistically validated for the determination of nitrofuran drug residues in poultry534. 

An example of a simple CZE method for peptide analysis and characterization is the one developed for protegrin IB-367.37 IB-367 is a peptide containing 17 amino acid residues that possess antimicrobial properties, and it is being developed for treatment of oral mucositis associated with aggressive cancer chemotherapy as well as other topical applications. This polycationic product was chemically synthesized using solid-phase and purified by preparative reversed-phase HPLC. IB-367 is rich in cysteine and arginine residues. 

Anthelmintic agents are a smaller, less diverse group than antimicrobial agents. They include levamisole and the benzimidazoles, and the newer avermectins. The benzimidazoles include thiabendazole which has also been used as a pesticide on plants and as a food preservative. Chemical methods have been used widely to quantify the residues of these substances in food, as part of national control programmes. They are an important sub-group of the antiparasitic agents that many consider to be essential for good animal husbandry. 

Microbiological inhibition tests are generally considered to be an unreliable method for detecting residues of antimicrobial agents in meat. The development of more specific, sensitive, reproducible, repeatable and robust chemical-based methods of analysis will offer methods capable of detecting residues previously undetectable by biological assays. 

Numerous methods are required to characterize drug substances and drug products (Chapter 10). Specifications may include description identification assay (of composite sample) tests for organic synthetic process impurities, inorganic impurities, degradation products, residual solvents, and container extractables tests of various physicochemical properties, chiral purity, water content, content uniformity, and antioxidant and antimicrobial preservative content microbial tests dissolution/disintegration tests hardness/friability tests and tests for particle size and polymorphic form. Some of these tests may be precluded, or additional tests may be added as dictated by the chemistry of the pharmaceutical or the dosage form. 

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