Comparison of the phenotypes of Streptococcus zooepidemicus isolated from tonsils of healthy horses and specimens obtained from foals and donkeys with pneumonia

Tohru Anzai Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099.
Present address is Epizootic Research Station, Tochigi Branch, Equine Research Institute, Tochigi 329-04, Japan.

Search for other papers by Tohru Anzai in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
John A. Walker Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099.
Present address is Program of Mathematics and Science, Midway College, 512 E Stephens St, Midway, KY 40347.

Search for other papers by John A. Walker in
Current site
Google Scholar
PubMed
Close
 PhD
,
Matthew B. Blair Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099.

Search for other papers by Matthew B. Blair in
Current site
Google Scholar
PubMed
Close
 MD
,
Thomas M. Chambers Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099.

Search for other papers by Thomas M. Chambers in
Current site
Google Scholar
PubMed
Close
 PhD
, and
John F. Timoney Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099.

Search for other papers by John F. Timoney in
Current site
Google Scholar
PubMed
Close
 MVB, DSc

Abstract

Objective—To determine whether streptococcal pneumonia is caused by strains of Streptococcus zooepidemicus similar to those obtained from the tonsils of healthy horses.

Sample Population—5 tonsils from healthy horses, 8 tracheal washes and 6 lung specimens from foals with pneumonia, and 5 nasopharyngeal swab specimens from donkeys with acute bronchopneumonia.

Procedure—Variable M-like protectively immunogenic SzP proteins of 5 isolates of S zooepidemicus from each tonsil and clinical specimen were compared, using immunoblots. The SzP gene of 13 isolates representative of various SzP immunoblot phenotypes from 1 healthy horse and 9 horses and donkeys with pneumonia were sequenced and compared. Cell-associated hyaluronic acid concentration and resistance to phagocytosis of some isolates were measured.

Results—Tonsils of each healthy horse were colonized by several SzP phenotypes similar to those of foals or donkeys with pneumonia. In contrast, multiple isolates from animals with pneumonia had the same SzP phenotype, indicating infection by a single strain or clone. Analysis of the SzP sequence confirmed that differences in immunoblot phenotype were associated with sequence differences and that several SzP genotypes were in healthy horses and animals with pneumonia. Isolates with high concentrations of cell-associated hyaluronic acid were more resistant to phagocytosis.

Conclusions and Clinical Relevance—An SzP-specific immunoblot is a useful, sensitive measure of diversity among strains of S zooepidemicus. Single strains with SzP phenotypes similar to those found in tonsils of healthy horses cause pneumonia. Because of the diversity of SzP phenotype and genotype among isolates from animals with pneumonia, SzP phenotype is not an important determinant of invasiveness or epizootic capabilities. (Am J Vet Res 2000;61:162–166)

Abstract

Objective—To determine whether streptococcal pneumonia is caused by strains of Streptococcus zooepidemicus similar to those obtained from the tonsils of healthy horses.

Sample Population—5 tonsils from healthy horses, 8 tracheal washes and 6 lung specimens from foals with pneumonia, and 5 nasopharyngeal swab specimens from donkeys with acute bronchopneumonia.

Procedure—Variable M-like protectively immunogenic SzP proteins of 5 isolates of S zooepidemicus from each tonsil and clinical specimen were compared, using immunoblots. The SzP gene of 13 isolates representative of various SzP immunoblot phenotypes from 1 healthy horse and 9 horses and donkeys with pneumonia were sequenced and compared. Cell-associated hyaluronic acid concentration and resistance to phagocytosis of some isolates were measured.

Results—Tonsils of each healthy horse were colonized by several SzP phenotypes similar to those of foals or donkeys with pneumonia. In contrast, multiple isolates from animals with pneumonia had the same SzP phenotype, indicating infection by a single strain or clone. Analysis of the SzP sequence confirmed that differences in immunoblot phenotype were associated with sequence differences and that several SzP genotypes were in healthy horses and animals with pneumonia. Isolates with high concentrations of cell-associated hyaluronic acid were more resistant to phagocytosis.

Conclusions and Clinical Relevance—An SzP-specific immunoblot is a useful, sensitive measure of diversity among strains of S zooepidemicus. Single strains with SzP phenotypes similar to those found in tonsils of healthy horses cause pneumonia. Because of the diversity of SzP phenotype and genotype among isolates from animals with pneumonia, SzP phenotype is not an important determinant of invasiveness or epizootic capabilities. (Am J Vet Res 2000;61:162–166)

Advertisement