Isolation And Identification And Preliminary Study On Biological Characteristics Of Escherichia Coli From Dairy Cow Mastitis In Intensive Dairy Farms In Shihezi Area

Dairy cow mastitis is one of the main diseases of dairy cows in intensive dairy farms.The disease has caused huge economic losses to dairy farms all over the country.However,there are few reports on mastitis in Shihezi area.Therefore,it is planned to investigate the mastitis infection of dairy cows in intensive dairy farms in Shihezi area of Xinjiang,in order to provide basic data for the diagnosis and prevention of bacterial cow mastitis in Shihezi area.In this study,a total of 106 milk samples were collected from 11 intensive cattle farms in Shihezi,Xinjiang from March 2022 to July 2022.Through isolation and identification of mastitis samples,biochemical identification and molecular detection,25 strains of Escherichia coli were finally obtained.The 25 strains of Escherichia coli isolates were subjected to phylogenetic grouping and virulence gene detection by PCR.The results showed that 25 strains of Escherichia coli belonged to 4 phylogenetic groups,of which 28%belonged to group A,52%belonged to group B1,and 8%belonged to group C.12%belonged to group E;the detection results of virulence genes of 25 strains of E.coli showed that 10virulence genes of adhesin and protein were detected in 16 virulence genes of adhesin,hemolysin,iron uptake system and other proteins,which were csg A,fim H,fim A,flu,luxs,esp A,pap,pta and mota,respectively.The detection rate of 5 virulence genes of csg A,fim H,luxs,pta and mota was 100%.It was found that 25 strains of E.coli carried at least 5 virulence genes.Whole genome sequencing results of 25 E.coli strains Serotype and multilocus typing were performed using Serotype Finder 2.0 and seven pairs of ST-type housekeeping genes.The results showed that 76%（19/25）of the 25 strains of E.coli were identified as serotype O,and the remaining 6 strains were not typed.The 19 strains of Escherichia coli belonged to 11 different serotypes,of which the most common were O101 serotype（5 strains）and O89 serotype（4 strains）.The results of multi-locus typing showed that only14 of the 25 E.coli strains had multi-locus sequence types,belonging to 11 ST types:ST4151,ST2169,ST10,ST711,ST154,ST1508,ST398,ST906,ST56,ST361,ST354,indicating that the ST types of 25E.coli strains were diverse,of which only ST10 accounted for 21.4%（3/14）slightly more than other ST types.The MIC method was used to analyze the drug sensitivity of 25 strains of E.coli.The results showed that the E.coli isolates were resistant to streptomycin,gentamicin,sulfamethoxazole,tetracycline,ceftiofur sodium,tylosin and azithromycin,and were only sensitive to polymyxin.And showed multiple drug resistance,6 or more antibiotic drugs accounted for 92%（23/25）.13 kinds of drug resistance genes were detected from 16 kinds of drug resistance genes of E.coli,which were oqxab,gyra,aac（6’）-Ib,Sul₁,Sul₂,Sul₃,bla _TEM,bla _CTX-M,aad A₁,aac C₂,aph（3’）-Ia,tet A and tet B,respectively.The detection rate of gyra and bla _TEMwas 100%.Statistics showed that 25 strains of E.coli carried at least 2 kinds of drug resistance genes.