China Animal Husbandry and Veterinary Medicine ›› 2021, Vol. 48 ›› Issue (1): 312-323.doi: 10.16431/j.cnki.1671-7236.2021.01.035

• Basic Veterinary Medicine • Previous Articles     Next Articles

Isolation,Identification and Drug Resistance Analysis of E.coli from Mastitis Milk in Shandong Province

YUAN Xiaomeng1,2, ZHAO Xiaonan2, LI Lulu2, ZHANG Qing2, HU Ming2, LUO Yanbo2, ZHANG Yin2, QI Jing2, LIU Yuqing1,2   

  1. 1. College of Life Science, Shandong Normal University, Jinan 250014, China;
    2. Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan 250100, China
  • Received:2020-04-16 Online:2021-01-20 Published:2021-01-15

Abstract: This experiment was aimed to estimate the contamination and drug resistance of E.coli in mastitis milk in Shandong.The large-scale dairy farms located in three regions of Shandong province were selected as the sampling sites for this study.A total of 227 milk samples were collected,the bacteriological method was used to isolate and identify E.coli,the micro-broth dilution method was used to detect 11 conventional antibacterial drugs,the 13 common drug resistance genes,8 virulence genes and class Ⅰ integron were screened by PCR.The results showed that a total of 71 E.coli strains were isolated from 227 milk samples.Antibiotic susceptibility testing of E.coli strains showed that strains which were resistant to one or more antibacterial drugs reached 77.5%,the multi-drug resistance rate was 15.5%,of which the resistance rate to polymyxin was 52.2%,and the amoxicillin-clavulanic acid resistance rate was 39.4%.However,all strains were sensitive to neomyci.Of the 71 E.coli strains,all of them carried blaTEM gene,and they were all blaTEM-1 gene,32.4% of the strains carried blaCTX-M gene,and most of them were blaCTX-M-15 gene.In addition,blaSHV and blaOXA genes were not detected;29.6% of the isolates carried mobile colistin resistance genes mcr-1;29.6% of the strains carried aac (6')-Ⅰb-cr gene,and 20.8% carried qnrB gene,qnrA and qnrC genes were not detected.For the analysis of 8 virulence genes,only Hly gene were not detected,and the detection rates of Ecs3703 and Irp2 genes were higher,which were 90.1% and 63.4%,respectively.Class Ⅰ integrons were detected in 11 strains,with a rate of 15.5%,and carried 6 types of gene cassettes,the prevalence of the gene cassette was dfr17-aadA5.The results indicated that the drug resistance of E.coli in mastitis milk in Shandong was serious.E.coli that carrying virulence genes Ecs3703 and Irp2 might be the pathogenic bacteria causing mastitis in dairy cow.The detection of class Ⅰ integrin played a key role in bacterial resistance and gene carrying rate.This study could provide a theoretical basis for clinical prevention and treatment colibacillosis of dairy cow mastitis.

Key words: E.coli; drug resistance; drug resistance gene; virulence gene; class Ⅰ integron

CLC Number: