The Regulatory Mechanism Of QseBC And McbR On The Antibiotic Resistance And Biofilm Formation In Escherichia Coli

Escherichia coli(E.coli)is one of the main pathogens causing infection in livestock and poultry.In recent years,the incidence of mastitis and colibacillosis caused by mammary pathogenic E.coli(MPEC)and avian pathogenic E.coli(APEC)is increasing year by year,leading to significant economic losses to the production of eggs,milk and meat of livestock and poultry industry worldwide.Antibiotic is an important treatment method to treat the pathogenic E.coli from livestock and poultry traditional,however,the abuse and misuse of antibiotics has contributed to the improvement of antibiotic-resistance level and the expansion of antibiotic-resistance spectrum in E.coli,and the emergence of multidrug-resistant E.coli.It is urgent to reveal the molecular mechanism and regulatory factors of multidrug resistance in pathogenic E.coli.It is reported that regulatory systems such as quorum sensing system,two-component system and transcriptional regulator play an important role in regulating the expression of drug-resistant genes and resisting bactericidal action from hosts or non-hosts.In this study,we explored the regulatory mechanisms of quorum sensing system and two-component system on the multidrug resistance of pathogenic E.coli from livestock and poultry(ECDCM2 and APECX40).The main results are as follows:1.The two-component Qse BC regulates antibiotic resistance and biofilm formation in avian pathogenic E.coli APECX40The two-component system Qse BC influences antibiotic resistance by regulating the transcription of efflux pump inhibitor acr R,efflux pump activator mar A and efflux pump related genes acr A,acr B,acr D,emr D and mdt H.And Qse BC enhances biofilm formation of APECX40 by up-regulating the transcription of biofilm associated genes bcsA,csgA,fliC,motA,wcaF and fimA.2.The two-component Qse BC regulates antibiotic resistance and biofilm formation in mammary pathogenic E.coli ECDCM2Qse B activates the expression of Mar A and regulates the transcription of acr A and acr B by binding directly to the promoter of mar A in ECDCM2.And Qse BC enhances biofilm formation of ECDCM2 by up-regulating the transcription of biofilm associated genes bcsA,csgA,fliC,motA,wcaF and fimA.3.McbR regulates antibiotic resistance in avian pathogenic E.coli APECX40The transcription regulator McbR activates the expression of the efflux pump associated proteins AcrAB,AcrD,AcrR,EmrD and MdtD by binding directly to the promoter regions of acr AB,acrD,acrR,emrD and mdtD,and then increasing the resistance of APECX40 to 12 antibiotics including lincosamides(clindamycin,lincomycin),?-lactams(cefotaxime,cefalexin),tetracyclines(doxycycline,tetracycline),aminoglycosides(gentamicin,kanamycin),quinolones(norfloxacin,ofloxacin),macrolides(erythromycin)and rifampin.4.Study on the relation between Rcs BC and Ari R,and the regulatory role of Rcs BC and Ari R in antibiotic resiatance and H₂O₂ pressure response in mammary pathogenic E.coli ECDCM2The two-component system Rcs BC increases antibiotic resistance of ECDCM2 to kanamycin,norfloxacin and ciprofloxacin;and Ari R decreases antibiotic resistance of ECDCM2 to kanamycin.However,Ari R reduces hydrogen peroxide pressure effect.In addition,?-galactosidase activity assay indicated that there is no regulatory relationship between Rcs BC and Ari R.In conclusion,this study revealed that the molecular mechanism of QseBC,RcsBC,McbR and AriR on regulating the multidrug resistance of ECDCM2 and APECX40 using antimicrobial activity assays,biofilm formation assays,hydrogen peroxide pressure effect,?-galactosidase activity assay,real-time reverse-transcription(RT)-PCR experiments,electrophoretic mobility shift assays(EMSA)and transcriptional profiling.Therefore,this study could provide potential drug targets and new clues for the prevention and treatment of the pathogenic E.coli infection from livestock and poultry.