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

BMC Microbiology

Research Article

Christian Bart¹  Katy Vaillancourt¹  Daniel Grenier¹  Laetitia Bonifait¹  Michel Frenette¹  Marcelo Gottschalk²  Maria de la Cruz Dominguez-Punaro²  Josh Slater³ 

[1] Groupe de Recherche en Écologie Buccale, Faculté de Médecine Dentaire, Université Laval, Quebec City, Quebec, Canada;Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Quebec, Canada;The Royal Veterinary College, Hatfield, UK;

关键词: Mutant Library;    Streptococcus Agalactiae;    Tn917 Insertion;    Tn917 Mutant;    Longe Generation Time;   

DOI  :  10.1186/1471-2180-10-42

 received in 2009-09-18, accepted in 2010-02-10,  发布年份 2010

来源: Springer

【 摘 要 】

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.

【 授权许可】

Unknown   
© Bonifait et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.