| Tigecycline is a new generation of tetracycline derivatives,which has the advantages of wide spectrum and can overcome the resistance mechanism of traditional tetracycline drugs.It is often used as the last line of defense drugs.However,in recent years,there have been more and more reports of ticacycline resistance,which were common in ICU.Escherichia coli,as one of the six most deadly microorganisms,has become resistant to a variety of antibiotics,which has caused concern among scientists.Although tigecycline has not been used in veterinary clinical practice,the study of tigecycline resistant strains of Escherichia coli from animal husbandry and its resistance mechanism is of great significance for understanding the cross-resistance between tigecycline and other antimicrobial agents,preventing major zoonotic diseases and guiding the clinical application of antimicrobial agents.This subject adopts the separation in unused for added ring element environment veterinary clinical isolated pig source sex Escherichia coli for ring element of resistant strains,explore its resistance mechanism to master resistance trend,find out the strain to add ring for drug resistance and its mechanism,for medical and veterinary medicine fully understand with non-contact ring element resistance and other provide theoretical basis for the correlation of drug resistance mechanism,provide reference for clinical rational use of antimicrobial agents.1?Preliminary study on the mechanism of drug resistance to tigecycline by drug-resistant bacteriaThe porcine strain of Escherichia coli,which had not been exposed to tigecycline,was collected from the surrounding areas of Chongqing from 2007 to 2008 as the test strain.Through the analysis of the resistance mechanism of the strain to tigecycline,the transcriptional amount of acrB,acrF,rpsJ,tet(B),oqxA,tet(X4),tet(M)genes were detected,and the MIC of the resistant strain was determined by selecting appropriate drainage pump inhibitors combined with tigecycline.The relationship curve between the effects of different concentrations combined with efflux pump inhibitors on drug-resistant strains and time was drawn.rpsJ si RNA interference assay was used to determine the survival rate of drug-resistant strains in subinhibitory concentration of tigecycline by absorbance.Results: There were significant differences in the transcriptional quantities of the efflox pump acrF,binding site rpsJ.The efflux pump inhibitor test showed that the MIC of drug-resistant strains decreased,and the combined efflux pump inhibitor had an obvious effect at the concentration of 1/2MIC tigecycline.The OD value of binding site rpsJ siRNA interference test was significantly lower than that of the control group at some time,and the difference was significant.Conclusions: The efflux pump acrF,binding site rpsJ and membrane pore protein jointly mediate the resistance of Escherichia coli to tigecycline.2?In vitro induction of Escherichia coli ATCC25922 and clinical tigecycline sensitive strains to obtain ticacycline resistant bacteriaUsing Escherichia coli and clinical isolates as research objects,multi-step method was used to induce in vitro from the starting point of subinhibitory concentration of doxycycline,respectively,and stable strains were obtained.The detection of drug resistance spectrum before and after induction by in vitro bacteriostatic test included the change of the minimum inhibitory concentration(MIC)of tigecycline to the tested strain.Results: The quality control strains induced by doxycycline successfully developed drug resistance to ticecycline,and the MIC of the induced strain was 256 times higher than that of the quality control strain.The clinical isolates susceptible to ticecycline were successfully induced by doxycycline to develop drug resistance to ticecycline,and the MIC of the resistant strain was 256 times higher than that before and after induction.Conclusion: Teccyclin-resistant strains do not need direct contact to develop,they may mutate through other pathways and share the same drug resistance mechanism with their drugs,showing cross-resistance of the same or other antimicrobial drugs.3?Research the mechanism of drug resistance induced in vitroThe changes in gene expression of acrB,acrF,rpsJ,tet(X4)induced by induced strains A(DOX)and 73-2(DOX)and the variation of bacterial binding site before and after induced by rpsJ were detected to observe the effect of CCCP combined with tigecycline on drug-resistant strains.Results: The test of efflux pump inhibitor showed that the MIC of drug-resistant strains decreased,and the effect of combined efflux pump inhibitor was obvious at the concentration of1/2MIC tigecycline.There were significant differences in the transcriptional amounts of efflux pump acrB,acrF binding site rpsJ.In the artificially induced clinical isolation of ticecycline sensitive strains,mainly tet(X4)was found.Conclusions: The quality control strain artificially induced by doxycycline is mediated by the efflux pump acrF,binding site rpsJ and membrane porin,and the resistance of E.coli to tigecycline is mainly mediated by the artificial induced clinical isolation of tigecycline sensitive strain,mainly by tet(X4). |
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