The cell envelope subtilisin-like proteinase is a virulence determinant for Streptococcus suis

Abstract

BackgroundStreptococcus suis is a major swine pathogen and zoonotic agent that mainly causes septicemia, meningitis, and endocarditis. It has recently been suggested that proteinases produced by S. suis (serotype 2) are potential virulence determinants. In the present study, we screened a S. suis mutant library created by the insertion of Tn917 transposon in order to isolate a mutant deficient in a cell surface proteinase. We characterized the gene and assessed the proteinase for its potential as a virulence factor.ResultsTwo mutants (G6G and M3G) possessing a single Tn917 insertion were isolated. The affected gene coded for a protein (SSU0757) that shared a high degree of identity with Streptococccus thermophilus PrtS (95.9%) and, to a lesser extent, with Streptococcus agalactiae CspA (49.5%), which are cell surface serine proteinases. The SSU0757 protein had a calculated molecular mass of 169.6 kDa and contained the catalytic triad characteristic of subtilisin family proteinases: motif I (Asp200), motif II (His239), and motif III (Ser568). SSU0757 also had the Gram-positive cell wall anchoring motif (Leu-Pro-X-Thr-Gly) at the carboxy-terminus, which was followed by a hydrophobic domain. All the S. suis isolates tested, which belonged to different serotypes, possessed the gene encoding the SSU0757 protein. The two mutants devoid of subtilisin-like proteinase activity had longer generation times and were more susceptible to killing by whole blood than the wild-type parent strain P1/7. The virulence of the G6G and M3G mutants was compared to the wild-type strain in the CD1 mouse model. Significant differences in mortality rates were noted between the P1/7 group and the M3G and G6G groups (p < 0.001).ConclusionIn summary, we identified a gene coding for a cell surface subtilisin-like serine proteinase that is widely distributed in S. suis. Evidences were brought for the involvement of this proteinase in S. suis virulence.

TroA of Streptococcus suis Is Required for Manganese Acquisition and Full Virulence

“…We used a well-established intraperitoneal mouse infection model (4,9,50) to assess virulence of the ⌬troA mutant. This demonstrated that TroA is required to cause systemic disease in mice.…”

“…To test the virulence of the ⌬troA mutant bacteria in systemic infection, we used a murine infection model broadly used to assess virulence of S. suis mutants (4,9,50). Ten CD1 mice were inoculated intraperitoneally with 10 9 CFU of wild-type or ⌬troA mutant bacteria.…”

The Streptococcus suis transcriptional landscape reveals adaptation mechanisms in pig blood and cerebrospinal fluid

“…sspA encodes a surface-associated subtilisin-like protease, which is capable of degrading IL-8, a major chemo-attractant of neutrophils . Deletion of sspA attenuated SS virulence in a mouse model and was more susceptible to killing by whole blood than the wild-type strain P1/7 (Bonifait et al 2010). This could be a potential way through which rss03 contributes to the survival of SS in blood.…”

Complete Genome Sequence of Streptococcus suis Serotype 14 Strain JS14

“…Overall, the cps locus in the JS14 genome showed strong similarity to that in serotype 1 strain identified earlier, which may explain why serotype-specific PCR method could not differentiate serotype 1 and serotype 14 (18). CDSs for a few virulence-associated factors, such as suilysin, extracellular protein factor, fibronectin/fibrinogen-binding protein (6), serum opacity-like factor (1), sortase A (15,19,20), peptidoglycan GlcNAc deacetylase (8), D-alanylated lipoteichoic acid (9), and subtilisin-like serine protease (3,4,12), which were confirmed to contribute to the virulence of serotype 2, were also found in the genome of JS14. Learning more about these factors would strengthen our understanding on the virulence of S. suis serotype 14.…”