Identification of variations in SzP proteins of Streptococcus equi subspecies zooepidemicus and the relationship between protein variants and clinical signs of infection in horses.
OBJECTIVE
To determine whether previously unidentified variations of the SzP protein of Streptococcus equi subsp zooepidemicus were present in horses with various clinical signs of infection and whether any relationship could be identified between SzP protein variants and naturally occurring clinical conditions.


METHODS
23 isolates of S equi subsp zooepidemicus were recovered from specimens of horses with various clinical conditions and used as a representative population of isolates for evaluation of different SzP protein variants.


METHODS
Genetic heterogeneity of the isolates was demonstrated by repetitive extragenic palindromic-polymerase chain reaction analysis. The SzP gene was sequenced and the presumed protein sequence determined for each isolate. Characteristics of the SzP proteins were compared among the isolates and in relation to the clinical conditions of horses from which they were recovered.


RESULTS
The signal peptide types, number of proline-glutamic acid-proline-lysine repeats, and anchor sequences were consistent with those previously described for the SzP protein. Many of the isolates clustered with 5 previously described types on the basis of the hypervariable region of the SzP protein. One additional variant, which represented 8 of the isolates, was identified. Particular motifs in the hypervariable region accounted for many of the differences among hypervariable types.


CONCLUSIONS
The SzP protein appears to be limited to a selected number of types. Variations in the SzP protein are frequently determined on the basis of different motifs rather than random amino acid substitutions. There does not appear to be any association of SzP protein variations and clinical manifestations of infection in horses.
Walker
Richard L
RL
California Animal Health and Food Safety Laboratory School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Runyan
Catherine A
CA
D000034:Abortion, Veterinary / Q000382:microbiology; D000038:Abscess / Q000382:microbiology / Q000662:veterinary; D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry / Q000235:genetics*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D002481:Cellulitis / Q000382:microbiology / Q000662:veterinary; D004716:Endometritis / Q000382:microbiology / Q000662:veterinary; D005260:Female; D014644:Genetic Variation; D006734:Horse Diseases / Q000382:microbiology* / Q000503:physiopathology*; D006736:Horses; D008198:Lymph Nodes / Q000382:microbiology / Q000473:pathology; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D011014:Pneumonia / Q000382:microbiology / Q000662:veterinary; D013290:Streptococcal Infections / Q000382:microbiology* / Q000503:physiopathology / Q000662:veterinary*; D018502:Streptococcus equi / Q000235:genetics*; D013530:Surgical Wound Infection / Q000382:microbiology / Q000662:veterinary
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C107892:SzPSe protein, Streptococcus equi