Novel Models of Streptococcus canis Colonization and Disease Reveal Modest Contributions of M-Like (SCM) Protein

Abstract

Streptococcus canis is a common colonizing bacterium of the urogenital tract of cats and dogs that can also cause invasive disease in these animal populations and in humans. Although the virulence mechanisms of S. canis are not well-characterized, an M-like protein, SCM, has recently identified been as a potential virulence factor. SCM is a surface-associated protein that binds to host plasminogen and IgGs suggesting its possible importance in host-pathogen interactions. In this study, we developed in vitro and ex vivo blood component models and murine models of S. canis vaginal colonization, systemic infection, and dermal infection to compare the virulence potential of the zoonotic S. canis vaginal isolate G361 and its isogenic SCM-deficient mutant (G361∆scm). We found that while S. canis establishes vaginal colonization and causes invasive disease in vivo, the contribution of the SCM protein to virulence phenotypes in these models is modest. We conclude that SCM is dispensable for invasive disease in murine models and for resistance to human blood components ex vivo, but may contribute to mucosal persistence, highlighting a potential contribution to the recently appreciated genetic diversity of SCM across strains and hosts.

Streptococcus canis sequence type 43 may be associated with treatment failure in dogs with corneal ulceration

“…24,30 To date it is unclear what role subtypes of scm have in virulence and recent evidence suggests any contribution would be modest. 25 The ability to form biofilms has been investigated in S canis as this allows bacteria to survive stressful events. A recent study characterized S canis ST21 and the presence of the ap1 gene was shown to be linked to biofilm production ability in this species.…”

Antibiotic-resistant status and pathogenic clonal complex of canine Streptococcus canis-associated deep pyoderma

“…This suggests that CC13 may be a group of highly virulent strains prone to cause disease in dogs. Although there have been reports of toxic shock syndrome caused by S. canis in dogs [ 28 , 29 ], few toxins from S. canis have been reported [ 30 , 31 ]. Because CC13 is likely to have toxic factors that are pathogenic to dogs, analyses of this cluster will likely identify virulence factors such as the s erythrogenic toxins of S. pyogenes .…”

Streptococcus canis, the underdog of the genus

“…Although according to some studies SCM appears to be linked to S. canis virulence (Fulde et al, 2011a(Fulde et al, , 2013, recent findings, based on comparisons between a wildtype strain and an SCM-deficient mutant, questioned the role of SCM in clinical infection (Cornax et al, 2021). The SCM-deficient mutant showed reduced ability to form biofilms compared to the wildtype, but haemolytic activity and survivability in the presence of aminising and oxidising agents were not impacted by the lack of scm.…”

“…When tested in vivo, the wildtype strain and the mutant were equally virulent in mouse models of dermal and systemic infection. The SCM-deficient strain, however, showed reduced adhesion and persistence in a murine model of vaginal colonisation when compared to the wildtype, suggesting that SCM might confer fitness advantages in particular anatomical sites (Cornax et al, 2021). Overall, the role of SCM as a virulence factor in S. canis is unclear with recent evidence suggesting a marginal involvement in disease progression.…”