Detection Of Virulence/resistance Of E.coli O157 And Virulence Epigenetic Regulation Research

Enterohemorrhagic Escherichia coli(EHEC)is a type of E.coli,which was first isolated in the United States in 1982 and can cause bleeding enteritis.E.coli 0157:H7 is a representative strain of EHEC.Since its discovery,0157:H7 has rapidly spread throughout the world and has become a threat to global public health security.There are two main problems to be solved in the prevention and treatment of E.coli 0157:H7:On the one hand,the pathogenic process of E.coli 0157:H7 depends on its own pathogenic factors;On the other hand,due to the abuse of antibiotics,E.coli 0157:H7 produces resistance and even multiple drug resistance.Therefore,the in-depth understanding of the pathogenic factors and drug resistance phenotypes of China's epidemic 0157:H7 and its intrinsic regulatory mechanisms has extensive applications in improving epidemic preparations,diagnosing risk assessments,and developing new drugs.In-depth study found that O157:H7 responds to host intestinal environment signals and regulates its own physiological metabolism(the expression of pathogenic factors)to adapt to colonic microenvironment to complete colonization during infection.Type 3 secretion system(T3SS),flagella,and other pathogenic factors play an important role in the process of 0157:H7 colonization of the intestine.However,the specific relationship between environmental signals and these pathogenic factors in bacterial infection is not yet clear.On the other hand,in recent years,a class of non-coding small RNAs(sRNAs)with regulatory functions have been discovered in all known bacteria,which are capable of undergoing the post-transcriptional regulation of many physiological metabolic processes(eg,nutrition adaptive regulation,quorum sensing,biofilm formation,motility,and pathogenesis mechanisms)in response to external environmental signals.In this paper,we first measure phenotype of the expression of the etiological factors(T3SS and flagella)in domestic 0157 and their MIC values for five antibiotics(ampicillin,ciprofloxacin,gentamicin,sulfamethoxazole,and tetracycline).From statistical analysis and bactericidal experiments,it was found that the sensitivity of 0157 to certain antibiotics is related to virulence genes.while the drug resistance mechanism of E.coli 0157 is more clearly studied and will not be discussed here.The sRNA MicA and RyhB,which are regulated by intestinal environmental signals such as NaCl/pH and iron ion concentration,can regulate the expression of flagella and T3SS,respectively.Among them,overexpression of MicA had different effects on the migration ability of 0157:H7 193 and K-12 BW25113 strains;over-expressed RyhB may regulate T3SS expression of 193 strains through base pairing with rraB mRNA.In this study,the pathogenic factor/drug resistant phenotype of E.coli 0157:H7 in China and the mechanism of sRNA-regulating flagella and T3SS expression were initially discussed,which has guiding significance for the prevention and control of E.coli 0157:H7.