Factors affecting the accuracy of the live animal swab test for detecting urine oxytetracycline and predicting oxytetracycline residues in calves.
The live animal swab test (LAST) was compared with quantitative oxytetracycline (OTC) assay of urine samples and tissue specimens to determine the accuracy of the LAST in detecting OTC in bovine urine and predicting violative residues in tissues. When urine OTC concentration was greater than 4.3 micrograms/ml, the LAST result was 100% accurate. When urine OTC concentration was less than 4.3 micrograms/ml, the LAST result was 60% accurate; 20% of the LAST results were false-positive, and 20% were false-negative. Urine osmolarity was highest (P less than 0.05) in samples with false-positive results and lowest (P less than 0.05) in samples with false-negative results. A similar trend was observed for urine pH, but was not statistically significant. Urine samples with false-positive results apparently had osmolarity and pH conditions that inhibited growth of Bacillus subtilis when OTC was lacking. False-negative results probably were obtained because urine osmolarity and pH conditions were favorable for the growth of bacteria even in the presence of OTC or because OTC concentration was below the limit of detection by the LAST. The LAST was inconsistent in detecting urine OTC in small concentrations and correspondingly failed to accurately predict OTC residues in tissues.
TerHune
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TN
Department of Anatomy and Physiology, College of Veterinary Medicine, Kansas State University, Manhattan 66506.
Upson
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DW
D000818:Animals; D002417:Cattle / Q000378:metabolism / Q000652:urine*; D004350:Drug Residues / Q000032:analysis*; D005260:Female; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000032:analysis; D008099:Liver / Q000032:analysis; D008168:Lung / Q000032:analysis; D008297:Male; D009132:Muscles / Q000032:analysis; D009994:Osmolar Concentration; D010118:Oxytetracycline / Q000032:analysis / Q000097:blood / Q000652:urine*; D011237:Predictive Value of Tests
D010118:Oxytetracycline