Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/18/2004
Publication Date: 5/15/2004
Citation: Schneider, M.J., Lehotay, S.J. 2004. A rapid fluorescence screening assay for tetracyclines in chicken muscle. Journal of Association of Official Analytical Chemists International. Interpretive Summary: Use of antibiotics in animals used for food has generated concern because the presence of these residues in food may lead to increased microbial resistance in humans. Tetracycline, oxytetracycline, and chlortetracycline are the three tetracycline type antibiotics approved for use in broiler chickens in the U.S. Considering the large number of chickens produced in the U.S., it is important to have efficient methods for monitoring levels of the tetracyclines in chicken. We have now developed a simple, rapid fluorescence screening assay for tetracyclines in chicken at the approved tolerance level of 2 mg/kg. The method involves homogenization of the chicken tissue in a basic solvent, centrifugation, addition of magnesium ions, and another centrifugation before the fluorescence of the resultant supernatant is measured. No overlap was observed between the fluorescence of control chicken extracts and those which had been fortified with 2 mg/kg of either tetracycline, oxytetracycline, or chlortetracycline. The method was tested with a set of blind fortified samples to illustrate the utility of this method as a screening assay. This procedure provides an alternative to microbial screening assays and represents a potentially useful tool for regulatory agencies such as FSIS.
Technical Abstract: A simple, rapid fluorescence assay was developed for screening tetracyclines in chicken muscle at the U.S. tolerance level (2 mg/kg). The method requires only a homogenization of the tissue in acetonitrile/ammonium hydroxide, centrifugation, addition of Mg+2 and another centrifugation before fluorescence of the supernatant is measured at 505 nm (excitation at 385 nm). Comparison of the fluorescence of control chicken muscle extracts with extracts from muscle fortified with either 2 mg/kg tetracycline, oxytetracycline or chlortetracycline showed no overlap. A threshold level set at the average fluorescence for a fortified 2 mg/kg sample minus 3 sigma minimized false negative responses to provide a successful screening method. The method was tested with blinded samples as controls or fortified with tetracycline, oxytetracycline or chlortetracycline in order to demonstrate its utility. This approach can provide an alternative to microbial screening assays.