Abstract
BackgroundStreptococcus suis serotype 2 is a major swine pathogen and zoonotic agent worldwide causing mainly meningitis and septicemia. Hyaluronate lyases are enzymes that degrade hyaluronic acid, a major constituent of animal tissues, and have been reported as virulence factors in various bacterial species. Since the hyaluronate lyase of S. suis has been considered ambiguously as a virulence factor, we screened 50 isolates from the three major clonal complexes found in North America (sequence type [ST] 1, ST25, and ST28) known to differ in their degree of virulence in order to link the presence or absence of this activity with the degree of virulence. Moreover, the effect of exogenous hyaluronic acid on S. suis virulence factor gene expression and the pro-inflammatory response of brain macrovascular endothelial cells (BMEC) was also investigated.ResultsWe found that all but one ST1 isolates (high virulence) were devoid of hyaluronate lyase activity whereas all ST25 (intermediate virulence) and ST28 (low virulence) isolates possessed the activity. A 2 bp insertion was responsible for the lack of activity in ST1 strains. Since the most virulent isolates did not degrade hyaluronic acid, this tissue component may be found during the infectious process. Therefore, we investigated its effect on S. suis and host cells. Hyaluronic acid was found to modulate S. suis adhesion to BMEC, to increase S. suis virulence factor expression, and to enhance pro-inflammatory cytokine secretion by BMEC.ConclusionsThese findings suggest that S. suis hyaluronate lyase does not represent a critical virulence factor in its active form. However, exogenous hyaluronic acid that is likely to interact with S. suis and host cells during the course of infection appears to modulate several virulence determinants of the bacterium, in addition to promote inflammation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13104-015-1692-9) contains supplementary material, which is available to authorized users.
Highlights
Streptococcus suis serotype 2 is a major swine pathogen and zoonotic agent worldwide causing mainly meningitis and septicemia
In the first part of this study, we investigated the distribution and genetic diversity of S. suis hyaluronate lyase among the three major sequence types (STs) of S. suis serotype 2 found in North America (ST1, ST25, ST28) that are known to differ in their degree of virulence, in order to provide an insight on the involvement of this protein in S. suis virulence
Comparison of the nucleic acid sequences between STs using S. suis serotype 7 hylA gene previously described as reference gene [18] showed the presence of four conserved insertions that occurred in ST1 strains (Fig. 2): a 21 bp insertion starting at position 192, a 3 bp insertion starting at position 330, a 2 bp insertion at Interestingly, the only ST1 strain (S735) that possessed hyaluronate lyase activity did not display the two last insertions in the hyaluronate lyase gene
Summary
Streptococcus suis serotype 2 is a major swine pathogen and zoonotic agent worldwide causing mainly meningitis and septicemia. The sialic-acid rich capsule is considered one of the most important virulence factors since acapsular mutants of S. suis were more susceptible to phagocytosis by macrophages and avirulent in animal models (piglet and mouse) [11, 12]. Additional virulenceassociated markers such as suilysin [13], extracellular factor [14], muraminidase-released protein [14], proteases [15, 16], and cell-wall anchored DNase [17] may contribute to S. suis pathogenesis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
