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Variation in the N-terminal region of an M-like protein of Streptococcus equi and evaluation of its potential as a tool in epidemiologic studies

Toru AnzaiEpizootic Research Center, Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Kokubunji-machi, Shimotsuga-gun, Tochigi 329-0412, Japan.

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 DVM, PhD
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Yasushi KuwamotoEpizootic Research Center, Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Kokubunji-machi, Shimotsuga-gun, Tochigi 329-0412, Japan.

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Ryuichi WadaEpizootic Research Center, Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Kokubunji-machi, Shimotsuga-gun, Tochigi 329-0412, Japan.

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Sigeo SugitaEpizootic Research Center, Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Kokubunji-machi, Shimotsuga-gun, Tochigi 329-0412, Japan.

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 PhD
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Tsutomu KakudaDepartment of Animal Hygiene, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan.

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Shinji TakaiDepartment of Animal Hygiene, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan.

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Tohru HiguchiMitsuishi Animal Clinic Center, Agriculture Mutual Aid Association of Hidaka District 200 Higashihohrai, Mitsuishi-cho, Mitsuishi-gun, Hokkaido 059-3105, Japan.

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John F. TimoneyGluck Equine Research Center, Department of Veterinary Science, College of Agriculture, University of Kentucky, Lexington, KY 40546-0099.

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 MVB, PhD, DSc

Abstract

Objective—To develop a method for typing Streptococcus equi on the basis of the DNA sequence of the genes that produce an M-like protein and to compare isolates among the United States, Japan, and other countries.

Sample PopulationS equi strains CF32, Hidaka/95/2, and NCTC9682 as well as 82 other isolates from the United States, Japan, and other countries obtained during 1975 to 2001.

Procedure—DNA sequences of the structural genes ( SeM and SzPSe) that produce M-like proteins were determined for 3 representative strains to find a variable region. Variability in this region of SeM was then determined for the other isolates. Amino acid sequences were deduced and analyzed phylogenetically by use of the neighbor-joining method.

Results—Sequence diversity was detected in the N-terminal region of SeM but not in SzPSe of the 3 representative strains. Base substitutions in the variable region of SeM varied in a nonsynonymous manner, resulting in variation in the amino acid sequence. Eighty-five isolates were categorized as 32 types of SeM on the basis of differences in the deduced amino acid sequences.

Conclusions and Clinical Relevance—This study documented a region in the N-terminal portion of SeM that varies in a nonsynonymous manner. This information should be useful in molecular epidemiologic studies of S equi. (Am J Vet Res 2005; 66:2167–2171)

Abstract

Objective—To develop a method for typing Streptococcus equi on the basis of the DNA sequence of the genes that produce an M-like protein and to compare isolates among the United States, Japan, and other countries.

Sample PopulationS equi strains CF32, Hidaka/95/2, and NCTC9682 as well as 82 other isolates from the United States, Japan, and other countries obtained during 1975 to 2001.

Procedure—DNA sequences of the structural genes ( SeM and SzPSe) that produce M-like proteins were determined for 3 representative strains to find a variable region. Variability in this region of SeM was then determined for the other isolates. Amino acid sequences were deduced and analyzed phylogenetically by use of the neighbor-joining method.

Results—Sequence diversity was detected in the N-terminal region of SeM but not in SzPSe of the 3 representative strains. Base substitutions in the variable region of SeM varied in a nonsynonymous manner, resulting in variation in the amino acid sequence. Eighty-five isolates were categorized as 32 types of SeM on the basis of differences in the deduced amino acid sequences.

Conclusions and Clinical Relevance—This study documented a region in the N-terminal portion of SeM that varies in a nonsynonymous manner. This information should be useful in molecular epidemiologic studies of S equi. (Am J Vet Res 2005; 66:2167–2171)