title: [Epidemiological investigation of Shiga toxin-producing Escherichia coli isolates originated from healthy sheep in one farm of Jiangsu Province and their pathogenicity].
abstract: OBJECTIVE
  In order to investigate the distribution of Shiga toxin-producing Escherichia coli (STEC) among healthy sheep in a farm and the pathogenicity to mice and Vero cells of these STEC isolates.
  
  
  METHODS
  We used polymerase chain reaction (PCR) to detect genes of eaeA, stx1, stx2, hlyA, which had been developed in this laboratory previously, combing the selective cultivation and Chrom-Agar (CA) O157 plates to isolate STEC strains.
  
  
  RESULTS
  A total of 107 STEC strains were isolated in a sheep farm during six visits from August, 2008 to January, 2009. The isolation rate was 19.8% (107/550). These isolates belonged to 41 O serotypes and 60 O: H serotypes, except that 21 were O non-typable and 1 was rough. 093 was the common serotype. Some isolates such as O5, O91, O103, which are reported in other countries originated from healthy sheep were also isolated in this study. Stx2 positive rate was higher than that of stxl. 50% lethal dose assay in mice indicated the pathogenicity of isolates was low and none of the 3 tested isolates caused mice death. We selected 107 stx gene positive STEC strains to induce the lambdoid bacteriophages. The results showed that 71 out of 107 isolates formed plagues, while 28 did not after induction. Detection of Shiga toxins for three tested isolates in Vero cell assay indicated one stx gene positive strain lacked the toxigenicity to Vero cells.
  
  
  CONCLUSIONS
  Sheep are the natural reservoirs of STEC and they are healthy to carry STEC. Although these STEC isolates experience low pathogenicity to mice, they are potential threat to human health. Shiga toxin gene positive were not equal to production of Shiga toxins, so we need to further study the Shiga toxin expression and regulation mechanism.
authors.affiliation: Key Laboratory of Animal Infectious Disease of Agriculture Ministry, College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, China. congcongjinan@163.com
authors.forename: Congcong
authors.initials: C
authors.lastname: Gu
authors.forename: Tao
authors.initials: T
authors.lastname: Xue
authors.forename: Tingting
authors.initials: T
authors.lastname: Xu
authors.forename: Song
authors.initials: S
authors.lastname: Gao
authors.forename: Xin'an
authors.initials: X
authors.lastname: Jiao
authors.forename: Xiufan
authors.initials: X
authors.lastname: Liu
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology; D001435:Bacteriophages / Q000472:pathogenicity; D002470:Cell Survival; D002681:China / Q000453:epidemiology; D002522:Chlorocebus aethiops; D004197:Disease Reservoirs / Q000382:microbiology; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission; D029968:Escherichia coli Proteins / Q000235:genetics*; D005407:Flagella / Q000276:immunology; D006460:Hemolysin Proteins / Q000235:genetics; D006801:Humans; D007928:Lethal Dose 50; D051379:Mice; D019081:O Antigens / Q000276:immunology; D016133:Polymerase Chain Reaction / Q000379:methods; D012703:Serotyping; D034561:Sheep, Domestic / Q000382:microbiology*; D022622:Shiga Toxin 1 / Q000235:genetics; D022641:Shiga Toxin 2 / Q000235:genetics; D022603:Shiga Toxins / Q000235:genetics*; D054323:Shiga-Toxigenic Escherichia coli / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification* / Q000472:pathogenicity*; D014709:Vero Cells
chemical_list: D018829:Adhesins, Bacterial; D000942:Antigens, Bacterial; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D019081:O Antigens; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; D022603:Shiga Toxins; C073819:eaeA protein, E coli