Study On Determination And Elimination Of Colistin Sulfate Residues In Chickens By A Microbiological Method

This study was designed to establish a rapid, sensitive microbiological method in testing residues of CLS in various tissues of domestic animals.The test organism used in this study was Bodetella Brochiseptica ATCC4617. Tissue samples of muscle, liver and kidney were collected and a standard regression curve for each tissue were made in accordance with the-dose theory. Computing quantity of CLS in samples based on the regression curve for the tissues. The detect limits of this test were 0.15 u g/g for the muscle tissue and 0.2 u g/g for the liver and kidney tissue that were lower than MRL of the EEC and the China Ministry of Agriculture .These regression curves for muscle, liver and kidney were satisfying linearity in the range of 0.025 u g/ml~6.4 u g/ml(r=0.9970,0.9994,0.9990; n=9,9,9). When CLS concentration was 0.05 u g/ml,0.2 u g/ml and 0.8 u g/ml respective, within-day coefficient of variation was 5.3%,3.6% and 3.4% respectively, between-day coefficient of variation was 4.3%, 2.4% and 3.0% respectively, the trial result indicate this method had good repetition. The mean recovery of muscle analysts at fortified level of 0.15 ug/g, 0.6 u g/g and 3.6 u g/g was 62.0%, 79.0% and 90.9% respectively, the coefficient of variation was 13.7%, 11.4% and 5.6% respectively ; the mean recovery of liver analysts at fortified level of 0.20 u g/g, 1 u g/g and 4 u g/g was 64.5%, 80.2% and 93.4% respectively, the coefficient of variation was 13.8%, 5.1% and 6.3% respectively ; The mean recovery of kidney analysts at fortified level of 0.20 u g/g, 1 u g/g and 4 u g/g was 65.0%, 81.8% and 95.9% respectively, the coefficient of variation was 14.1%, 7.2% and 6.0% respectively.This study first tested the sensitivity of Bodetella Brochiseptica ATCC4617 to some drugs and the results showed that Bodetella Brochiseptica ATCC4617 had high specificity to CLS, but chloramphenicol and kanamycin maybe intefered with detecting result of the CLS and caused a false positive test, so the identification of CLS demand to link with some methods such as HPLC.CLS was administered at dose levels of 60mg/L and 300mg/L in chicken in the drinking water. CLS activity was not detected in these samples for muscle tissue, could be detected trace amount of CLS in liver and kidney tissues in 300mg/L group at Oh.