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 Population—S 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;