Isolation,identification and biological characteristics of Escherichia coli from di-arrhea of calves in a dairy farm in Kunming
To clarify the pathogenic bacteria causing calf diarrhea and the biological characteristics of pathogenic bacteria in a dairy farm in Kunming,the bacterial isolation and culture,biochemical tests and 16S rRNA assays were performed on calf diarrhea feces to identify bacterial species.In addition,pathogenicity tests,serotype,virulence gene,drug sensitivity,drug resistance gene and population typing detection were conducted on the isolated bacteria.The results showed that four strongly pathogenic Escherichia coli(E.coli)strains were isolated and identified from the feces of calves with O3,O4 and O103 as the dominant serotypes;the four pathogenic E.coli strains exhibi-ted strong resistance to gentamicin,cefazolin,chloramphenicol,ciprofloxacin and norfloxacin,while they were moderately susceptible to butylamine cara;the isolates had blaOXA,blaTEM,aac(6')-Ib,oqxAB,aadA1 and nine kinds of virulence genes such as fimH,Crl,iucD,astA,hlyE,ompA,ompC,K88,papC,and the four pathogenic strains were all type B2 E.coli.The results revealed that the type B2 pathogen causing calf diarrhea in a dairy farm in Kunming showed strong resist-ance to common clinical antibiotics and carried multiple resistance and virulence genes.This study provides a reference for the selection of effective therapeutic drugs for calf diarrhea in this dairy farm.
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