[Method of determining bacitracin residues in animal husbandry food products]

Distribution of bacitracin in rabbits when given orally was studied. It was found that bacitracin was absorbed from the gastrointestinal tract, penetrated into the organs and tissues, was partially bound there and rapidly excreted with the urine and bile. The highest percentage of the antibiotic binding was registered in the bone marrow and organs of the lymphoid system. Since the binding of the antibiotic was selective (only in the organs of the lymphoid system) and its presence in the muscle tissue and subproducts (liver, kidneys, etc.) was in the trace amounts, they do not prevent the use of such products in food. Thermal treatment of such products eliminates the antibiotic activity which is also in favour of their use. Therefore, bacitracin may be widely used as a growth stimulator in cattle breeding. For detection of the bacitracin bound fraction in the organs, tissues and animal products it is recommended to use enzymatic hydrolysis of the biological substrates containing bacitracin with a 2 per cent pepsin solution prepared in phosphate buffer, pH 6.0-6.2.