ABSTRACT
To obtain iron, a necessary nutrient, meningococci and several other human and veterinary pathogens have iron-acquisition systems, which are expressed in vivo during infection. One target of iron-acquisition systems is transferrin (Tf), which is the major glycoprotein responsible for the transport of iron in the extracellular milieu of vertebrates. Tf-binding proteins A and B (TbpA and TbpB) function as the cell-surface Tf receptor in Neisseria meningitidis (1).
ABSTRACT
The recent recognition of streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis (NF) in dogs caused by Streptococcus canis highlights our 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 examined for the presence of 10 Streptococcus pyogenes-associated virulence genes by Southern hybridizations using gene probes generated by PCR. The isolates lacked DNA with homology to eight of the 10 gene probes (speA, speB, speC, mf, ssa, scp, 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 phagocytosis in canine blood. Electron microscopy revealed the presence of proteinaceous 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.
Subject(s)
Bacterial Outer Membrane Proteins , Dog Diseases/microbiology , Fasciitis, Necrotizing/veterinary , Membrane Proteins , Shock, Septic/veterinary , Streptococcus/pathogenicity , Amino Acid Sequence , Animals , Antigens, Bacterial/analysis , Bacterial Proteins/analysis , Base Sequence , Carrier Proteins/analysis , Dogs , Exotoxins/analysis , Fasciitis, Necrotizing/microbiology , Molecular Sequence Data , Phagocytosis , Shock, Septic/microbiology , Streptococcus/isolation & purification , Streptokinase/analysis , Streptolysins/analysis , Superantigens/analysisABSTRACT
The emergence of streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis (NF) in dogs caused by Streptococcus canis has been reported by our laboratory. Since clonal expansion is thought to be partially responsible for the spread of invasive strains of Streptococcus pyogenes in humans, the relatedness of 15 isolates of S. canis from canine STSS and/or NF was examined using pulsed field gel electrophoresis and biotyping; production of proteases and of a CAMP-like reaction were also examined. Only 2 of the 15 STSS and/or NF isolates were clonally related, suggesting that the emergence of canine STSS/NF is not the result of clonal expansion of one or more highly virulent strains of S. canis. All of the isolates produced proteases and demonstrated a CAMP-like reaction, which appear to be additional characteristics of S. canis.
