Virulence of Streptococcus canis from canine streptococcal toxic shock syndrome and necrotizing fasciitis

The recent recognition of streptococcal toxic shock syndrome (STSS) and nec rotizing fasciitis (VF) in dogs caused by Streptococcus canis highlights ou r lack of knowledge regarding the mechanisms of virulence of this organism. Fifteen isolates of S. canis from cases of canine STSS and/or NF were exam ined for the presence of 10 Streptococcus pyogenes-associated virulence gen es by Southern hybridizations using gene probes generated by PCR. The isola tes lacked DNA with homology to eight of the 10 gene probes (speA, speB, sp eC, mf, ssa, sep, hasA, ska) under low stringency conditions. Thirteen and 15 of 15 isolates hybridized with streptolysin O and M protein gene probes, respectively. Twelve of 15 S. canis isolates were resistant to phagocytosi s in canine blood. Electron microscopy revealed the presence of proteinaceo us cell surface fibrillae. These results suggest that S. canis possesses M proteins and encodes streptolysin O, but lacks some of the other recognized virulence genes with significant homology to those in S. pyogenes. (C) 199 9 Elsevier Science B.V. All rights reserved.