| Multidrug-resistance (MDR) and extensively drug-resistance (XDR) have been popular along with the increasing occurrence of bacterial year by year. However, the research and development of new antimicrobials is slow,but also the price of them is high. It is reasonable to use the existing antimicrobials again. The re-application of existing drug, especially can not cause drug resistance, can be used as the first choice to control the disease caused by multi-drug resistant strains. In the present study, we intended to examine the prevalence of florfenicol resistance and plasmid-mediated floR resistance genes among E.coli isolates from chicken. Current findings will be helpful to prevent the emergence of florfenicol resistance, and give new ideas for dissolving the problem of dissemination of resistance determinants in veterinary clinic.A total of 80 E.coli isolates in Changzhou province during 2013 and 2014 were included in this study. PCR was first used to detect plasmid-mediated florfenicol resistance floR genes and broth dilution method was used to evaluate the minimum inhibitory concentrations(MIC)of drugs from 80 avian E. coli isolates, phylogenetic group were carried out to analyze the polygenetic and clonal relatedness of floR-positive isolates of different origins.The conjugation experiments of 78 positive strains obtained uncertain conjugon which were identified through two methods minimum bacteriostasis concentration and PCR, and analyze the minimum bacteriostasis concentration among recipient bacterium, donor bacterium and the conjugon, also include the transfer condition of floR drug resistance gene. Select a small amount of conjugation experiments successful strains for the S1-PFGE and do the research about transmission and drug resistance gene location of floR through the Southern hybridization method The results of this study are as follows:The positive rate of floR gene in 80 pathogenic E. coli from chicken origin strains is 97.5% (78/80) that suggest the high prevalence of floR gene in E. coli. The drug resistance rate for different medicines is in details below:96.25%(77/80) for amoxicillin, florfenicol followed by 90%(72/80), colistin 80%(64/80), streptomycin 75%(60/80), enrofloxacin 72.5%(58/80), doxycycline 56.25%(45/80), apramycin 18.75%(15/80). This result demonstrated that the avian Escherichia coli showed a serious resistance to most drugs in this study.According to the phylogenetic analysis in E. coli, the nonpathogenic strains (A) is 35% (28/80) which is identical with low pathogenic strains (B1), and highly pathogenic strains (B2) is 2.5%(2/80) while 27.5%(22/80) in highly pathogenic strains-D.The rate of conjugation experiments is 65.38%(51/78), and the MIC value of floR conjugon for florfenicol has increased 16 to 32 times than recipient bacterium while decreased 2 to 8 times than donor bacterium. Meanwhile, the MIC value of conjugon For amoxicillin, colistin, streptomycin, enrofloxacin, doxycycline, amoxicillin also change.In conclusion,the tolerance of florfenicol and other common medicine exit common transfer infect. All 51 strains of conjugon include the floR drug resistance gene. The detected results indicate that the plasmids of selected strains including TM10 TM12 and WJ13are large plasmids about 130-210kb in size. |
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