title: Long-term excretion of Shiga toxin-producing Escherichia coli (STEC) and experimental infection of a sheep with O157.
abstract: To investigate a long-term shedding of Shiga toxin (Stx)-producing Escherichia coli (STEC) from sheep, a fifteen-month study for STEC isolation from a sheep, which had yielded STEC before, was attempted. The sheep continued to shed STEC and 39 STEC were isolated. The number of STEC in the feces was estimated at 1.7 x 10(3) per gram. In addition, although Stx1-negative O157 and stx2-encoding bacteriophage were experimentally infected to the sheep, Stx-positive O157 or Stx2- producing bacterial cells were not detected. The genetical and biochemical characterization of those 39 STEC strains showed that all STEC strains produced Shiga toxin 1 (Stx1) and were divided into three classes (I to III). From phylogenetic analysis of their amino acid sequences, class-I STEC was classified as group 1 comprising mainly human STEC, and classes II/III were as group 2 comprising sheep STEC. Our results suggest that STEC easily colonized in sheep and that the sheep continued to shed STEC, showing that sheep might be an important reservoir for human STEC infection.
authors.affiliation: Department of Veterinary Microbiology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan.
authors.forename: Suk
authors.initials: S
authors.lastname: Kim
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Asakura
authors.forename: Asumi
authors.initials: A
authors.lastname: Kuri
authors.forename: Masahisa
authors.initials: M
authors.lastname: Watarai
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Shirahata
authors.forename: Kouichi
authors.initials: K
authors.lastname: Takeshi
authors.forename: Teizo
authors.initials: T
authors.lastname: Tsukamoto
authors.forename: Sou-ichi
authors.initials: S
authors.lastname: Makino
mesh_terms: D000818:Animals; D004197:Disease Reservoirs; D004927:Escherichia coli Infections / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology*; D005243:Feces / Q000382:microbiology*; D010802:Phylogeny; D012703:Serotyping; D034561:Sheep, Domestic / Q000382:microbiology*; D022603:Shiga Toxins / Q000302:isolation & purification*; D013997:Time Factors; D015047:Zoonoses / Q000382:microbiology
chemical_list: D022603:Shiga Toxins