Effect Of LsrR Gene Knockout On Drug Resistance In Avian Pathogenic Escherichia Coli

Avian pathogenic E.coli is one of the most common pathogenic bacteria in the livestock industry,Avian pathogenic E.coli infection of poultry diseases,will increase the death rate of poultry and bring huge economic losses.Transcription experiments confirmed that the knockout of lsrR would affect the transcription level of more than 100 genes in E.coli,which are involved in biological membrane formation,transcriptional regulation,protein expression under pressure and nutrition acquisition and other physiological activities.The transporter MdtH in MFS efflux pump was resistant to norfloxacin.This experiment revealed the effect of lsrR deletion on mdtH of drug-resistant gene,and further explained the regulatory mechanism of lsrR on mdtH of drug-resistant gene.1.The resistance of norfloxacin,ofloxacin,ciprofloxacin and tetracycline to WT(AEPC 40)and XY10(AEPC 40AlsrR)was verified by two-fold dilution method.The MIC values of WT and XY10 were the same for the four antibiotics.The CFU method was used to test the effect of antibiotics on the resistance of WT and XY10.The results showed that the influence of the four antibiotics on WT and XY10 was consistent,and the CFU value of XY10 was more than twice higher than that of WT.2.Overexpression of lsrR and mdtH was constructed.Under the pressure of the four antibiotics,the MIC value of overexpressed strain WT/pUCIsrR was eight times lower than that of WT/pUC 19 and XY10/pUC 19,and the MIC value of overexpressed strain WT/pUClsrR in tetracycline was four times lower than that of WT/pUClsrR and XY10/pUC 19.Under the four antibiotics,the CFU of WT/pUC1srR was more than five times lower than that of WT/pUC 19,and the CFU of WT/pUCmdtH was more than three times higher than that of WT/pUC 19.This suggests that the absence of IsrR may have a regulatory effect on mdtH.3.RT-qPCR was used to verify the transcription levels of mdtH gene in WT/pUC 19,WT/pUCIsrR,WT/pUCmdtH,WT/pSTV28,XY10/pSTV28 and XY10/pClsrR strains.The results showed that the absence of IsrR could up-regulate the transcription level of mdtH.4.Specific binding of mdtH gene promoter region to LsrR protein was detected by EMSA.Therefore,it was proved that LsrR protein directly regulated the transcription of drug-resistant gene mdtH.Further study of this study may provide new drug targets and treatment ideas for the treatment of Avian pathogenic E.coli.