Isolation and Identification of Avian Pathogenic Escherichia coli in Parts of Hunan Province and Analysis on Its Biological Characteristics
In order to explore the biological characteristics of avian pathogenic Escherichia coli(APEC)in Hunan Province,122 clinical liver samples were collected from dead chickens on some intensive farms for bacteria isolation,cultivation and preliminary identification,then the housekeeping gene phoA of Escherichia coli was amplified by PCR,followed by serotype identification,detection of phylogenetic group,multi-site sequence typing(MLST),virulence gene testing,animal pathogenicity testing and drug resistance analysis for the purified and identified isolates.The results showed that 83 strains of APEC were isolated and 15 serotypes were identified,in which,O2,O1,O78 and O14 were dominant,phylogenetic groups included B2,Bl,AandD,and most of the highly pathogenic strains belonged to B2 and B1 group;12 ST types were obtained through MLST analysis,in which,ST95,ST481 and ST350 were the main types;for the isolates,virulence genes of irp2,fyuA,iutA and fimC were100％carried,and 38.55％isolates carried irp2,afa,fyuA,iutA,hlyF,iss,papC andfimC,simultaneously;through pathogenicity test,46(55.42％)highly pathogenic strains,31(37.35％)moderately pathogenic strains and 6(7.23％)low pathogenic strains were detected;and the isolates were resistant to 10 common antibiotics to different extent,especially to tetracycline and novobiocin,with the resistance rate reaching 96.38％and 92.77％,respectively.In conclusion,the whole genetic relationship of APEC,with high pathogenicity and wide drug resistance,was complex and polymorphic in Hunan Province,indicating an urgency to further prevent and control the disease in the region.
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