Title: A Rapid Fluorescence Assay for Danofloxacin in Beef Muscle. Effect of Muscle Type on Limit of Quantitation Author
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 11, 2008
Publication Date: N/A
Interpretive Summary: Use of fluoroquinolone antibiotics in animals used for food has generated concern because the presence of these residues in food may lead to increased antibiotic resistance in humans. It is important to have efficient methods for monitoring levels of these residues in the food supply to ensure they are below the tolerance set by the U.S. Food and Drug Administration. We have now successfully applied a rapid fluorescence screening method for determination of danofloxacin in beef muscle at the tolerance level of 200 ng/g. The method involves homogenization of the beef muscle in acidic acetonitrile, centrifugation, and measurement of the fluorescence of the resultant supernatant. The method was tested with blind samples to illustrate its utility. A comparison of the method using three different types of beef muscle (hanging tenderloin, neck, and eye round steak), as well as serum determined that the sensitivity of the method depended on the type of muscle used, with hanging tenderloin and neck muscle providing significantly greater sensitivity than that obtained with eye round steak or serum. This work not only provides regulatory agencies such as FSIS a potentially useful screening method for danofloxacin in beef muscle, but shows that different types of beef muscles may provide different levels of sensitivity in such assays.
Technical Abstract: A simple, rapid fluorescence screening assay was applied to the analysis of beef muscle for danofloxacin at the U.S. tolerance level of 200 ng/g. Muscle samples were homogenized in acetic acid/acetonitrile, the resultant mixture centrifuged, and fluorescence of the supernatants was then measured. The significant difference between the fluorescence of control muscle sample extracts and extracts of samples fortified at 200 ng/g allowed for successful discrimination between the samples. Setting a threshold level at the average 200 ng/g fortified sample extract fluorescence - 3s allowed for identification of potentially violative samples. Successful analysis of a group of blind fortified samples over a range of concentrations, was accomplished in this manner without any false negative results. The limits of quantitation for danofloxacin, as well as enrofloxacin using this assay were determined in three types of beef muscle (hanging tenderloin, neck, and eye round steak), as well as in serum. Significant differences in LOQ were found among the three different muscle types examined, with hanging tenderloin muscle providing the lowest value. This work not only shows the potential for use of the fluorescence screening assay as an alternative to currently used microbial or antibody-based assays for the analysis of danofloxacin in beef muscle, but suggests that assays using beef muscle may vary in performance depending on the specific muscle selected for analysis.