Submitted to: Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2013
Publication Date: 4/1/2013
Citation: Schneider, M.J., Yun, L., Lehotay, S.J. 2013. Terbium-sensitized luminescence screening method for fluoroquinolones in beef serum. Food Additives & Contaminants. 30(4):666-669.
Interpretive Summary: Use of fluoroquinolone (FQ) antibiotics in animals used for food has generated concern as the presence of these residues in food may lead to increased antimicrobial resistance in humans. It is important to have efficient methods to monitor the food supply to ensure that levels of these residues are below the limits set by the U.S. Food and Drug Administration. Preliminary screening tests are often used to increase the efficiency of monitoring, but such commonly used tests are insensitive to FQs. We have now developed a simple screening method for FQs in cattle which uses serum, thus allowing for more rapid extraction of any residues present, and the possibility of testing prior to slaughter. This approach takes advantage of the DNA-enhanced luminescence of terbium (III)-FQ complexes. The method gives excellent sensitivity and has been tested with blind samples to illustrate its utility. This work provides regulatory agencies such as FDA and FSIS with a method for rapid, sensitive screening of beef serum for FQ residues.
Technical Abstract: Enrofloxacin is one of only two fluoroquinolone antibiotics approved for use in cattle in the U.S. Microbial screening methods commonly used for monitoring veterinary drug residues are not sensitive or selective for fluoroquinolones. In this work, a luminescence-based screening assay was developed to detect enrofloxacin in beef serum. This approach takes advantage of the DNA-enhanced luminescence signal of an enrofloxacin-Tb (III) complex. In this method, serum samples are extracted with acidified acetonitrile in the presence of magnesium sulfate. After centrifugation, evaporation of the supernatant is followed by dissolution of the residue in buffer and filtration. Addition of Tb (III) and DNA then allows reading of the luminescence signal. Good recoveries (73-88%) at 25, 50 and 100 ng/mL were achieved with this approach, and the limit of detection was found to be 2.5 ng/mL based on the variability of response of control samples from 18 different steers. The method was used to test quantitative screening over a range of 0-100 ng/mL enrofloxacin using blind samples.