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Phylogenetic diversity and similarity of active sites of Shiga toxin (Stx) in Shiga toxin-producing Escherichia coli (STEC) isolates from humans and animals

Published online by Cambridge University Press:  28 August 2001

H. ASAKURA
Affiliation:
Department of Veterinary Microbiology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan
S-I. MAKINO
Affiliation:
Department of Veterinary Microbiology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan
H. KOBORI
Affiliation:
Department of Veterinary Microbiology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan
M. WATARAI
Affiliation:
Department of Veterinary Microbiology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan
T. SHIRAHATA
Affiliation:
Department of Veterinary Microbiology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan
T. IKEDA
Affiliation:
Hokkaido Institute of Public Health, Sapporo, Hokkaido 060-0819, Japan
K. TAKESHI
Affiliation:
Hokkaido Institute of Public Health, Sapporo, Hokkaido 060-0819, Japan
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Abstract

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Nucleotide sequences of Shiga toxin (Stx) genes in STEC from various origins were determined and characterized by phylogenetic analysis based on Shiga toxin (Stx) with those deposited in GenBank. The phylogenetic trees placed Stx1 and Stx2 into two and five groups respectively, and indicated that Stx1 in sheep-origin STEC were placed into a different group from those in other STEC, and that Stx2 of deer-origin STEC also belonged to the unique group and appeared to be distantly related to human-origin STEC. On the other hand, Stx of STEC isolated from cattle, seagulls and flies were closely related to those of human-origin STEC. Such a diversity of Stx suggested that STEC might be widely disseminated in many animal species, and be dependent on their host species or their habitat. In addition, the active sites in both toxins were compared; the active sites in both subunits of Stx in all the animal-origin STEC were identical to those in human-origin STEC, suggesting that all the toxin of STEC from animals might be also cytotoxic, and therefore, such animal-origin STEC might have potential pathogenicity for humans.

Type
Research Article
Copyright
2001 Cambridge University Press