Trigger factor of Streptococcus suis is involved in stress tolerance and virulence

Streptococcus suis serotype 2 is an important zoonotic pathogen that causes serious diseases such as meningitis, septicemia, endocarditis, arthritis and septic shock in pigs and humans. Little is known about the regulation of virulence gene expression in S. suis serotype 2. In this study, we cloned and deleted the entire tig gene from the chromosome of S. suis serotype 2 SC21 strain, and constructed a mutant strain (Delta tig) and a complementation strain (C Delta tig). The results demonstrated that the rig gene, encoding trigger factor from S. suis serotype 2 SC21, affects the stress tolerance and the expression of a few virulence genes of S. suis serotype 2. Deletion of the tig gene of S. suis serotype 2 resulted in mutant strain. Delta Tig, which exhibited a significant decrease in adherence to cell line HEp-2, and lacked hemolytic activity. Tig deficiency diminishes stresses tolerance of S. suis serotype 2 such as survive thermal, oxidative and acid stresses. Quantification of expression levels of known S. suis serotype 2 SC21 virulence genes by real-time polymerase chain reaction in vitro revealed that trigger factor influences the expression of epf, cps, adh, rpob, fbps, hyl, sly, mrp and hrcA virulence-associated genes. Delta Tig was shown to be attenuated in a LD50 assay and bacteriology, indicating that trigger factor plays an important part in the pathogenesis and stress tolerance of S. suis serotype 2 infection. Mutant Delta Tig was 100% defective in virulence in CD1 mice at up to 107 CFU, and provided 100% protection when challenged with 107 CFU of the SC21 strain. (C) 2010 Published by Elsevier Ltd.