Clones of Streptococcus zooepidemicus from Outbreaks of Hemorrhagic Canine Pneumonia and Associated Immune Responses

Abstract

ABSTRACTAcute hemorrhagic pneumonia caused byStreptococcus zooepidemicushas emerged as a major disease of shelter dogs and greyhounds.S. zooepidemicusstrains differing in multilocus sequence typing (MLST), protective protein (SzP), and M-like protein (SzM) sequences were identified from 9 outbreaks in Texas, Kansas, Florida, Nevada, New Mexico, and Pennsylvania. Clonality based on 2 or more isolates was evident for 7 of these outbreaks. The Pennsylvania and Nevada outbreaks also involved cats. Goat antisera against acutely infected lung tissue as well as convalescent-phase sera reacted with a mucinase (Sz115), hyaluronidase (HylC), InlA domain-containing cell surface-anchored protein (INLA), membrane-anchored protein (MAP), SzP, SzM, and extracellular oligopeptide-binding protein (OppA). The amino acid sequences of SzP and SzM of the isolates varied greatly. Theszpandszmalleles of the closely related Kansas clone (sequence type 129 [ST-129]) and United Kingdom isolate BHS5 (ST-123) were different, indicating that MLST was unreliable as a predictor of virulence phenotype. Combinations of conserved HylC and serine protease (ScpC) and variable SzM and SzP proteins ofS. zooepidemicusstrain NC78 were protectively immunogenic for mice challenged with a virulent canine strain. Thus, although canine pneumonia outbreaks are caused by different strains ofS. zooepidemicus, protective immune responses were elicited in mice by combinations of conserved or variableS. zooepidemicusproteins from a single strain.