title: Characterization and virulence clustering analysis of extraintestinal pathogenic Escherichia coli isolated from swine in China.
abstract: BACKGROUND
  Swine extraintestinal pathogenic Escherichia coli (ExPEC) is an important pathogen that leads to economic and welfare costs in the swine industry worldwide, and is occurring with increasing frequency in China. By far, various virulence factors have been recognized in ExPEC. Here, we investigated the virulence genotypes and clonal structure of collected strains to improve the knowledge of phylogenetic traits of porcine ExPECs in China.
  
  
  RESULTS
  We isolated 64 Chinese porcine ExPEC strains from 2013 to 14 in China. By multiplex PCR, the distribution of isolates belonging to phylogenetic groups B1, B2, A and D was 9.4%, 10.9%, 57.8% and 21.9%, respectively. Nineteen virulence-related genes were detected by PCR assay; ompA, fimH, vat, traT and iutA were highly prevalent. Virulence-related genes were remarkably more prevalent in group B2 than in groups A, B1 and D; notably, usp, cnf1, hlyD, papA and ibeA were only found in group B2 strains. Genotyping analysis was performed and four clusters of strains (named I to IV) were identified. Cluster IV contained all isolates from group B2 and Cluster IV isolates had the strongest pathogenicity in a mouse infection model. As phylogenetic group B2 and D ExPEC isolates are generally considered virulent, multilocus sequence typing (MLST) analysis was performed for these isolates to further investigate genetic relationships. Two novel sequence types, ST5170 and ST5171, were discovered. Among the nine clonal complexes identified among our group B2 and D isolates, CC12 and CC95 have been indicated to have high zoonotic pathogenicity. The distinction between group B2 and non-B2 isolates in virulence and genotype accorded with MLST analysis.
  
  
  CONCLUSIONS
  This study reveals significant genetic diversity among ExPEC isolates and helps us to better understand their pathogenesis. Importantly, our data suggest group B2 (Cluster IV) strains have the highest risk of causing animal disease and illustrate the correlation between genotype and virulence.
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Yinchu
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Wenyang
authors.initials: W
authors.lastname: Dong
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Jiale
authors.initials: J
authors.lastname: Ma
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Lvfeng
authors.initials: L
authors.lastname: Yuan
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Hassan M A
authors.initials: HM
authors.lastname: Hejair
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Zihao
authors.initials: Z
authors.lastname: Pan
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Guangjin
authors.initials: G
authors.lastname: Liu
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China. yaohch@njau.edu.cn.|Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China. yaohch@njau.edu.cn.
authors.forename: Huochun
authors.initials: H
authors.lastname: Yao
mesh_terms: D000818:Animals; D002681:China / Q000453:epidemiology; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D000072282:Extraintestinal Pathogenic Escherichia coli / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity*; D014644:Genetic Variation; D051379:Mice; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D013552:Swine / Q000382:microbiology; D013553:Swine Diseases / Q000453:epidemiology / Q000382:microbiology*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics
chemical_list: D037521:Virulence Factors
keywords: Genotype; Multilocus sequence typing; Porcine extraintestinal pathogenic Escherichia coli; Virulence