Evaluation of a multiple bioassay technique for determination of antibiotic residues in meat with standard solutions of antimicrobials.

A multiple bioassay technique (FSIS-USDA) has been evaluated with standard solutions of 38 antibiotics and sulphonamides. Activity patterns at five levels were obtained when antibiotic solutions were assayed on seven plates prepared with different media and microorganisms. A different activity pattern was obtained for the main antibiotic groups: tetracyclines, beta-lactam antibiotics, macrolides and aminoglycosides. Sulphonamides were not detected at levels at under 100 micrograms/ml. This technique, as a post-screening test for antibiotic residues, can be used after a screening test to identify antibiotic groups to which more specific techniques can be applied for full identification and quantification.