| A cylinder plate microbiological assay with Escherichia Coli,Staphylococcusaureus,Bacillus Subtilis and Micrococcus luteus was developed for determination ofNorfloxacin,Enrofloxacin,Ciprofloxacin and the mixture residues in different tissuesof chicken. Firstly, in order to verify the precision and the feasibility of this method ,the detection limits of three drugs in PBS,muscle,liver and kidney were detected.Secondly, the standard response curves were drawn and the analysis on the linerconnection to the logarithm of the drug concentration and the diameter of therestraining circle was conducted to obtain the respective liner regress equation and thecorrelative coefficient. And the recovery rate was detected to verify the feasibility ofthis method. Finally, the residues of three drugs and their mixture in chicken tissueswere detected in different time by the method we established. The results: there are differences among the detection limit of three drugs withthe same bacteria and the same tissues in PBS; and the differences among thedetection limits of the same drug with the different bacteria and the same tissue inPBS. In PBS, The detection limit of different drugs for different bacteria was0.025-0.40μg/ml; In muscle, The limit of detection was 0.05-0.60μg/ml; and in liverand kidney, was 0.075-0.090μg/g. The detection limit of Enrofloxacin was loweramong three drugs. The Micrococcus luteus has the highest sensitivity against thesethree drugs and the lowest detection limit, which was 0.025μg/ml. The cylinder plate of three drugs:The standard response curves of these fourbacteria to these three drugs were obtained through experiment. The linear range ofdrugs was from the detection limit to 5 times of the limit. The coefficients of variation(CV) were all above 0.99. Among the cylinder plates the Micrococcus luteus had thehighest slope which showed that its sensitivity was the highest against these threedrugs. The E.coli has lower sensitivity and the Bacillus subtilis has the lowestsensitivity. The recovery rate of three drugs: The recovery rate and the detection precision ofthree drugs and their mixture were detected. the results were given as follow: therecoveries rate were all above 70%, the CV were below 15%, which could respond tothe fidelity and precision. The recovery rate of E. coli and Staphylococcus in threedrugs and their mixture were higher than Bacillus subtilis and Micrococcus luteus; therecovery rate in liver and kidney was higher than that in muscle; the recovery rate ofthe mixture of three drugs is higher than that of the three drugs separate, and the CValso was the lowest of the mixture. The detection of residues of three drugs: the residues of three drugs in differenttime were detected with microbiological method in tissues of boiler .The ciprofloxac-in can be detected among 24 hours which showed that the residue was large.Micrococcus luteus has the highest sensitivity in detection of three drugs and theirmixture. So the Micrococcus luteus can detect the residue of three drugs and theirmixture in all time which means this bacteria is a excellent bacteria in detection of theresidues of FQs. These four bacteria can detect the residues of the mixture of threedrugs after they were fed to the broiler 24h later except the bacillus subtilis , whichcan't detect them between 1 hour and 2 hours. And the residues in kidney is higherthan that in muscle and liver. It was concluded that although the E.coli ,Staphylococcus aureus, Bacillussubtilis and Micrococcus luteus has different sensitivity against different drugs,theyall can be used to detect the residues of FQs. Microbiological method was practical,fast, steady and easy to perform, which can be used in the detection of the residues ofFQs in the tissues of broiler. |
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