Molecular Epidemiological Investigation Of APEC In Parts Of East China

Escherichia coli is a type of commensal strains which typically colonizes the gastrointestinal tract of human and animals.Most of Escherichia coli have no pathogenicity,but some of them not.They are sufficient to acquire a combination of mobile genetic elements to become a highly adapted pathogen capable of causing a range of diseases.Avian pathogenicity Escherichia coli is a type of extraterrestrial E.coli which attributes to cause a broad spectrum diseases.E.coli infections in avian species have been extremely popular and been an economic threat to the poultry industry worldwide.Due to the difference of locations,countries and regions,popularity of APEC has their own characteristic respectively.We investigated some regions in eastern China for studying the prevalence of etiology and molecular epidemiology of APEC.We have gone to a few poultry farms to survey pathological examination of chicken and pathogen isolation were performed.All of isolates were primary identified and analyzed by the way of bacteriology,and then tested the pathogenicity and lethality by infecting 7 days old chicken.The molecular biology and epidemiology of 77 APEC isolated from septicemic poultry were further investigated by polymerase chain reaction(PCR),phylogenetic analysis and multi-locus sequence typing.To prevent and control outbreaks of APEC,we test their antimicrobial susceptibility of 9 antibiotics,so that we can provide additional information for production.1 The virulence and phylogenetic group of APEC:The high pathogenicity of APEC attributes to the various virulence genes.In this research,we identified 26 virulence genes,such as adhesion,iron-acquisition systems,type VI secretion systems,antiserum survival factors.Some of them are very prevalent,for example,the relevant ratio of fimC,mat,iss and ompA is 94.8%,98.7%,81.8%and 97.4%respectively.However,there were also some prevalent low virulence genes.Their relevance ratio was less than 20%.The afa,hlyA,sat and cnfl genes were absent in this 77 strains.Depending on previous research,B2 and D groups were high pathogenicity and prevalent group.But in this epidemic research,group B2 and D occupy nearly a half proportion,what left were group A and group B1.Besides of this,the virulence genes average number of A,B1,D,B2 was 9,7.3,12.6,13.4 respectively.There was no significant difference between B2,D and A,groups about the average number of virulence genes,which indicated that A group also may be a high pathogenicity group.2 The molecular epidemiology investigation by multi-locus sequence type and antimicrobial susceptibility test for APEC:The ST117 was the most prevalent among those isolated strains,ST23 was the second,and then was ST95.Their relevance ratio was 15.6%,9.1%,and 6.5%respectively.Depending on previous research,ST95 was the most prevalent type which was diverse from this research.Moreover,the lethality and pathogenicity test implied that those ST117 strains possessed strong pathogenicity,and antimicrobial susceptibility test suggested that those strains also had potent antibiotics resistance.However,the pathogenesis and drug resistance mechanism needs to further study.The result of antimicrobial susceptibility of 9 antibiotics implied that the drug resistance of 77 APEC generally very high,especially for ampicillin which belong to(3-lactamases and sulfa drugs,and most susceptible drug was amikacin which belong to aminoglycosides antibiotics.