PARTICLE CONCENTRATION FLUORESCENCE IMMUNOASSAY FOR DETERMINATION OF TYLOSIN IN PREMIX, FEEDS, AND LIQUID FEED SUPPLEMENT - COMPARISON WITHTURBIDIMETRIC ASSAY

A rapid, competitive particle concentration fluorescence immunoassay ( PCFIA) for the determination of tylosin (Tylan) concentrations in extr acts of premix, feeds (cattle, chicken, and swine), and liquid feed su pplement is described. Tylosin-beta-phycoerythrin conjugate, tylosin s tandard or diluted sample extracts, and rabbit anti-tylosin antibody a re incubated for 15 min in PCFIA plates. Rabbit anti-tylosin antibody is then captured, during a 15 min incubation, with goat anti-rabbit an tibody that is attached to latex beads. Assay plates are washed to rem ove unbound tylosin-beta-phycoerythrin and unbound, free tylosin. Fluo rescence is measured with a fluorimeter. Tylosin concentration is inve rsely proportional to the beta-phycoerythrin fluorescence signal. The method, evaluated and validated with an IDEXX Screen Machine, shows hi gh specificity with regard to compounds expected to be found in the pr esence of tylosin, and results correlate well with traditional turbidi metric assay results. Hydrolysis of TUA (tylosin-urea adduct), necessa ry with microbiological methods, and cleanup of extracts beyond filtra tion are unnecessary with the PCFIA for tylosin.