Microbiological screening assay for tylosin in pollen

Summary

Tylosin has been isolated from pollen samples by adsorption on acidic mixed-mode solid-phase extraction cartridges, with subsequent determination using a disk-diffusion microbiological assay. While not providing identification of individual antibiotics present, the presence of a zone of inhibition provides a simple indication of the presence of bacteriostatic/bactericidal residues. Use of Paenibacillus larvae gave reproducible sensitivity to 0.2 mg/kg tylosin, but not reliably below that level. Of the strains of bacteria tested, P. larvae and Micrococcus luteus gave the greatest sensitivity and inhibition zone diameter; M. luteus was sensitive to some component of pollen, giving large blanks, and less sensitive than other strains to low concentrations of tylosin. Sampling provides the greatest source of error in the analysis of pollen.

Keywords:

• antibiotic residues
• recovery
• determination