| Escherichia coli is one of the normal intestinal flora,which is beneficial to human body under normal conditions.However,it becomes the conditional pathogens when the immune system declines.Escherichia coli,which can cause intestinal infections,including gastroenteritis and diarrhea,is called Diarrheagenic Escherichiacoli(DEC).Foreign studies have shown that the detection rate of DEC in patients with diarrhea was17.4% to 28.0%,while in domestic studies of the detection rate of the bacterium was slightly lower,from 12.7% to 18.9%.It is now the leading cause of the global infectious diarrhea outbreak and endemic diarrhea.According to their different pathogenicity,we divided them into different types,Enteropathogenic E.coli(EPEC),Enterotoxigenic E.coli(ETEC),Enteroinvasive E.coli(EIEC),Enterohemorrhagic E.coli(EHEC),Enteroadherent E.coli(EAEC).Traditional methods of DEC detection include selective medium culture,biochemical identification and serological identification and other methods.However,the morphology of these strains is similar to that of ordinary Escherichia coli.The positive rate of traditional cultivation and serum agglutination methods is low,and the virulence genes and virulence intensity of the same serotype are different,which makes it difficult to trace the source of infection in clinical diagnosis outbreak.Escherichia coli diarrhea caused by many serotypes,prone to cross-aggregation phenomenon.As a new technique,molecular typing can rapidly and accurately detect pathogenic genes of pathogens and clearly reflect the carrying status and characteristics of pathogenic genes in different individuals.It has been widely used in study of the pathogen tracing and genetic evolution of strains of infectious diseases outbreak in the academic field.Diarrheal Escherichia coli is one of the most common pathogenic bacteria in clinical practice and is an important pathogen that threatens human health.Due to the extensive,continuous and improper use of antibiotics,the increasing number of drug-resistant strains and the continuous change of drug resistance mechanism,especially the emergence of multiple cross-resistant strains make clinical treatment of diarrhea-causing Escherichia coli diseases become very difficult.The resistance of diarrheal Escherichia coli has attracted wide attention from the domestic and international medical field.In ourcountry,the resistance rate of most bacteria is higher than that in Europe and the United States,seriously affecting the clinical treatment.The clinical application of antimicrobial medicine is always accompanied by the emergence of bacterial resistance.Pathogenic bacteria in different regions at different times have various resistance to antibiotics,thus understanding of the distribution and drug resistance of clinical pathogens in the region can provide a strong basis to selection and utilization of antibiotics clinically.Objective: The pathogenicity and drug resistance of Diarrheagenic Escherichiacoli will be discussed by investigating the virulence genes of diarrheal Escherichia coli,molecular typing of PFGE and drug susceptibility in local,combining gene typing and drug susceptibility.To provide a proof on the diversity and molecular epidemiology of Diarrheagenic Escherichiacoli study and establish a reliable traceability system for foodborne diseases.Methods: The suspected strains of Diarrheagenic Escherichiacoli was isolated from feces of patients with diarrhea in Zibo from 2014 to 2017.The collected trains was by refreshed and identified.Virulence genes were detected by PCR.PFGE molecular typing and bacterial susceptibility tests were carried out on strains carrying virulence genes between 2016 and 2017 to explore the homology and pathogenicity of the strains.Results:(1)There were 124 strains out of 609 suspected Diarrheagenic Escherichiacoli were identified having virulence gene.In the 124 trains,83 strains were EAEC,25 strains were ETEC,14 strains were EPEC,1 strain was EHEC and 1 strain was EIEC.The main pathogens were EAEC,accounting for 66.94% of all positive bacteria,accounting for13.63% of the suspicious DEC submitted for inspection.There were 57 strains of EAEC carrying ast A virulence genes,accounting for 68.67% of EAEC.(2)The results of PFGE typing showed that isolates carrying virulence genes were distantly related and had no obvious dominant banding pattern.The highest similarity of DNA bands was 100%.The relatively high similarity was 93.55%,90.48% and 85.37%,the others were below 85%,and the lowest similarity was only 9.36%.(3)The result of drug susceptibility test showed that 92 strains of diarrheal Escherichia coli in 2016-2017 had the highest resistance to quinolones.24 strains of Diarrheagenic Escherichiacoli were ESBLs-positive,accounting for 26.09%.The drug resistance of ESBLs bacteria was higher,among which the resistance rates to penicillins,cephalosporins,quinolones and aztreonam were significantly higher.The drug resistance rate of Ampicillin,Cefazolin,Cefotaxime Sodium,Aztreonam was increasing from 63.04%,38.04%,30.43% to 95.83%,100%,100% respectively.While they were almost completely sensitive to imipenem,meropenem and amoxicillin / clavulanic acid.Conclusions:(1)The Diarrheagenic Escherichiacoli in food-borne diseases in Zibo was mostly EAEC.Most EAEC only carried ast A virulence genes.(2)PFGE-type of Diarrheagenic Escherichiacoli was not obvious in image category relevance,and its genetic relationship was far.(3)Diarrheagenic Escherichiacoli in food-borne diseases in Zibo has serious drug resistant,and the resistance to quinolones is the highest.ESBLs positive strain has a high proportion,and the spread of drug resistance among different strains should be taken seriously. |
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