title: Molecular characterization of cytolethal distending toxin gene-positive Escherichia coli from healthy cattle and swine in Nara, Japan.
abstract: BACKGROUND
  Cytolethal distending toxin (CDT)-producing Escherichia coli (CTEC) has been isolated from patients with gastrointestinal or urinary tract infection, and sepsis. However, the source of human infection remains unknown. In this study, we attempted to detect and isolate CTEC strains from fecal specimens of healthy farm animals and characterized them phenotypically and genotypically.
  
  
  RESULTS
  By PCR analysis, the cdtB gene was detected in 90 and 14 out of 102 and 45 stool specimens of healthy cattle and swine, respectively, and none from 45 chicken samples. Subtypes of the cdtB genes (I to V) were further examined by restriction fragment length polymorphism analysis of the amplicons and by type-specific PCRs for the cdt-III and cdt-V genes. Of the 90 cdtB gene-positive cattle samples, 2 cdt-I, 25 cdt-III, 1 cdt-IV, 52 cdt-V and 1 both cdt-III and cdt-V gene-positive strains were isolated while 1 cdt-II and 6 cdt-V gene-positive were isolated from 14 cdtB positive swine samples. Serotypes of some isolates were identical to those of human isolates. Interestingly, a cdt-II gene-positive strain isolated from swine was for the first time identified as Escherichia albertii. Phylogenetic analysis grouped 87 E. coli strains into 77 phylogroup B1, 6 B2, and 4 D, respectively. Most of the B1 strains harbored both lpfAO113 and ehaA. Three and twenty-two cdt-V gene-positive strains harbored eaeA and stx genes, respectively, and seven possessed cdt-V, stx and subAB genes. The cnf2 gene, normally present in cdt-III gene-positive strains, was also detected in cdt-V gene-positive strains.
  
  
  CONCLUSIONS
  Our results suggest that healthy cattle and swine could be the reservoir of CTEC, and they could be a potential source of human infections.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hinenoya
authors.forename: Kensuke
authors.initials: K
authors.lastname: Shima
authors.forename: Masahiro
authors.initials: M
authors.lastname: Asakura
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nishimura
authors.forename: Teizo
authors.initials: T
authors.lastname: Tsukamoto
authors.forename: Tadasuke
authors.initials: T
authors.lastname: Ooka
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hayashi
authors.forename: Thandavarayan
authors.initials: T
authors.lastname: Ramamurthy
authors.forename: Shah M
authors.initials: SM
authors.lastname: Faruque
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58 Rinku ourai-kita, Izumisano, Osaka 598-8531, Japan. shinji@vet.osakafu-u.ac.jp.
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamasaki
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics*; D002417:Cattle; D002645:Chickens; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D007564:Japan; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D013552:Swine
chemical_list: D001427:Bacterial Toxins; D004269:DNA, Bacterial; C067044:cytolethal distending toxin
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