| Escherichia coli is a common pathogen of clinical infection,antibiotic treatment is the most important means.However,the unreasonable use of antibacterial drugs in humans and animals exacerbates the emergence of multi-drug resistance of the strain,leading to treatment failure or weakening treatment efficacy,which seriously affects livestock production development and physical health of human and animals.The production of bacterial enzyme is one of the main causes of bacterial resistance.As one of the important challenges of antibiotic resistance,the extended spectrum ?-lactamase(ESBLs)are common in Klebsiella pneumoniae,E.coli etc.The main purpose of this paper was to investigate the drug-resistant phenotype,genotype prevalence and epidemiologyical feature of ESBL-EC.Results provide assistance for drug resistance treatment and prevention of ESBLs in clinically and analyzing the mechanism of drug resistance level transfer.1.Analysis of drug resistance of Escherichia coli467strains of pigs and chickens collected from different ages conducted with K-B susceptibility test.The K-B susceptibility test showed resistance to AMP,KZ,TE mostly,and the resistance rates were 44.2%,47.6%,and 59.3%,respectively.Some strains exhibit multi-drug resistance,the drug resistance ratio of AMP,SXT,TE,FOS,NOR,CN increased by the years,the resistance ratio of AMP,SXT,TE,FOS,NOR and CN in 2010-2018 were 73.1%and 57.7%,78.8%,9.6%,48.1%,40.4%,respectively2.Detection of ESBL-EC and its drug resistance analysisESBL-EC were detected by three different methods(double-disk diffusion confirmed method,VITEK Compact2.0,chromogenic medium).Finally,16 strains of E.coli about 32.7%of all isolates were confirmed as ESBL-EC.The sensitivity of the three identification methods was 88.9%,94.1%,and 88.9%,respectively,which were able to effectively detect ESBLs-positive strains.16 strains ESBL-EC showed resistant to AMP(100%),KZ(93.8%),FEP(75%),CTX(100%),TE(93.8%),LEV(75%),SXT(81.3%),CL(62.5%),NOR(75%).The genotype identification was mainly CTX-M-1 group gene(blaCTX-M-1,blaCTX-M-28,blaCTX-M-69,blaCTX-M-79)and CTX-M-9 group gene(blaCTX-M-14,blaCTX-M-z7,blaCTX-M-65),another blaSHV-108 gene type ESBL-EC was isolated.In addition,11 strains of bacteria were also detected to carry TEM-1 type p-lactamase(68.8%).3.16 strain ESBL-EC sequnce typingTo confirm the homology of the strains of 16 ESBL-EC,common classification methods such as MLST typing,Phylo-group aassignment typing and ERIC typing were used in this paper.Phylo-group assignment result showed that among the 16 strains of ESBL-EC,8 strains of A group(50%),5 strains of B1 group(31.3%),1 strain of B2 group(6.3%),and 2 strains of D group(12.5%).The E.coli ERIC typing results showed that 16 strains ESBL-EC were divided into five groups of G1-G5.The results of MLST typing showed that 14 ESBL-EC strains were divided into 7 ST types,ST2,ST21,ST43,ST53,ST132,ST471,and ST479 respectively,and 2 strains could not judge sequence type.4.Detection of multi-drug resistant horizontal element of ESBL-ECThe analysis of drug-resistant horizontal element showed that 15 strains integrase I were detected,integrase ? was not detected.For integrase-positive strains amplified integron variou region,of 11 strains positive.Three kind of target fragment were amplified,727 bp,1580 bp and 3000 bp,of which carrying drfA25,dfrA17 and aadA5,aacA4 and cmlA1 resistance genes,respectively.14 strains of insert sequence ISEcp1(14/16),9 strains of ISCR1(9/16)and 1 strain of IS26(1/16)were detected in 16 strains ESBL-EC totally.6 strian of ESBL-EC CTX-M-9 group were conducted with plasmid conjugation experiment,4 zygotes were obtained(Con1374?Con1376?Con1390-2?Con1393).The zygote is resistant to AMP,KZ,CTX,TE,etc.through the zygosity plasmid. |
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