| In order to study the dose-effect relationship between the drug-resistance of the intestinal bacteria and residues, Cynoglossus semilaevis Gunther were fed for 11 days with the fish feedstuff,to which OTC was added with dose of 125 mg/(kg·d) under the seawater temperature (22±1)℃. During and after the administration period, for monitoring the response of the resistance of the intestinal bacteria and Vibrio.spp, the resistance rates of which were investigated using the OTC selection mediums, meanwhile, OTC residues in the muscle, serum and liver were detected by HPLC, for assisting the safe,reasonable administration and prediction of withdrawal time. Finally, the 18 fitting curves between the resistance rates and the OTC residues were obtained by fitting both, a new thinking of drug detection will be provided during the culture process of aquatic animals.⑴Identification of counting mediums and concentrations of OTC added in the selection mediumsAfter the analyses of bacteria quantity,the stability and parallelism of quantity, MNA and MTCBS were selected as the suitable mediums for cultivation of the bacteria and Vibrio.spp in the intestine and seawater and used in the following study. Searching for the suitable concentrations of the selection mediums, Three levels of OTC concentrations, 16,80 and 160μg/ml were added in the two mediums, MNA and MTCBS. The result shows good dispersibility and linear relationship with the concentrations. So 16,80 and 160μg/ml were used in the the following study.⑵I mpact of drug-resistance of the intestinal bacteria and Vibrio.spp with administration of OTCThree concentration of OTC , 16,80and 160μg/ml were added in the MNA and MTCBS, as the test mediums of three OTC resistance levels, low,moderate and high. The large change of resistance rates for the intestinal bacteria and Vibrio.spp was investigated after the administration. After the comprehensive analysis, the results as follows:①The resistance rates basically increase during the administration period,reach the maximums respectively at the last day, and decreased significantly after feeding deprivation without the outside OTC stress, till to or close to the control level.②The resistance rates of Vibrio.spp is bigger than rates of the intestinal bacteria in the same OTC resistance level, both resistance rates decreased with the increase of OTC concentrations added in the respective mediums. At the last day of administration, 6 kinds of resistance rate–time curves reached a maximum level respectively. The resistance rate of the Vibrio.spp with the low level resistance reached the maximum(75.23±3.39)% and the resistance rate of the bacteria with the high level reached the minimum among them.③At the end of the withdrawal period, the low resistance level of Vibrio.spp decreased to the control level of the resistance, with the rest rates still above the control levels.⑶Analysis of the OTC residues in the tissuesDuring the the administration period, the OTC residues in the muscle, serum and liver showed a balance of accumulation and elimination, reached the maximum value (3.14±0.27)μg/g,(3.05±0.29)μg/ml and(7.20±1.17)μg/g at the 7th,4th and 7th respectively, decreased during withdrawal period,till under the detection limit of 0.05μg/g, with the withdrawal time 10,8and 12d.⑷The fitting relationship between the resistance rates and residuesAfter analysis of the resistance rate and the residues of the tissues during the withdrawal period, a good relativity between them was obtained. The residues of the fish tissues can be checked by the inspection of the resistance rates by the 18 fitting curves. So the detection time of drug residues was shorted,and the control level of aquatic products will be improved.The resistance rates of the intestinal bacteria and Vibrio.spp was inspected, using the selection mediums NA and MTCBS, during and after the administration of OTC to Cynoglossus semilaevis Gunther. The resistance rates have a good relativity with the residues of the three fish tissues. This study is not only for enrichment of the content of microbial ecology, but also supplies a new study method and theoretical basis for establishment of safety control model, which is used for the monitoring the quantity and intensity of drug administrated during aquaculture by the model of indicative bacteria in the ecological environment. |
PDF Full Text Request