Microbiological turbidimetric analysis of low chlortetracycline concentrations in feeds.
Recovery studies in which chlortetracycline hydrochloride (CTC-HCI) standard was added to cattle and swine feed supplements at 4.09-9.99 g/ton showed lower antibiotic recovery turbidimetrically (80.6-98.7%) than by the AOAC modified standard as in 38.179(d) (91.2-98.7%) and the plain buffer as in 38.179(b) (93.8-133.0%) methods. Three feeds fortified with a commercial premix at the levels of 5.0 and 10.0 g CTC-HCI/ton showed an overall CTC-HCI recovery of 87.6-110.6% by manual turbidimetric assay. Results were 89.1-108.7% by the AOAC inactivated feed diluent standard and 95.4-125.4% by the plain buffer methods. For some sample extracts (as in cattle feed) the use of heat to stop bacterial growth in the turbidimetric method caused formation of a precipitate. Cooling of cultures to room temperature and rapid reading of sample turbidity followed by standard curve concentrations minimized this interference. The manual turbidimetric assay of low levels of CTC-HCI in feeds appears to offer advantages over other methods.
D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D002417:Cattle; D002751:Chlortetracycline / Q000032:analysis* / Q000494:pharmacology / Q000592:standards; D005069:Evaluation Studies as Topic; D006358:Hot Temperature; D008826:Microbial Sensitivity Tests; D009391:Nephelometry and Turbidimetry; D013210:Staphylococcus / Q000254:growth & development
D002751:Chlortetracycline