Development of colloidal gold-based immunochromatographic assay for rapid detection of Streptococcus suis serotype 2.

To develop colloidal gold immunochromatographic strips for the direct detection of the Streptococcus suis serotype 2 antigen, colloidal gold was prepared by reduction of a gold salt with sodium citrate and coupled with polyclonal antibody against S. suis serotype 2. The optimal concentrations of the capture antibody and the coating antibody were determined to be 22mug/mL and 2.0mg/mL, respectively, and that of the blocking buffer was determined to be 1.5% bovine serum albumin. Different serotypes of S. suis and other related bacteria were used to evaluate the sensitivity, specificity, and stability of the immunochromatographic strips. The detection sensitivity was found to be as high as 10(6)CFU/mL. There was no cross-reaction of the antibodies with other serotypes of S. suis (except with SS1/2, which shares some common sugar residues or antigenic determinants with serotype 2) and other related bacteria. In conclusion, we developed colloidal gold immunochromatographic strips that had high sensitivity and specificity. This method proved to be feasible, convenient, rapid, and effective for detecting S. suis serotype 2.

Proteome analysis of Streptococcus suis serotype 2.

Outbreaks in humans, caused by Streptococcus suis serotype 2 (SS2), were reported in 1998 and 2005 in China. However, the mechanism of SS2-associated infection remains unclear. For the first time, a 2-D gel approach combined with MS was used to establish a comprehensive 2-D reference map for aiding our understanding of the pathogenicity of SS2. The identification of 694 out of 834 processed spots revealed 373 proteins. Most of the identified proteins were located in the cytoplasm and were involved in energy metabolism, protein synthesis, and cellular processes. Proteins that were abundant in the 2-DE gels could be linked mainly to housekeeping functions in carbohydrate metabolism, protein quality control and translation. 2-DE of secretory proteins was performed using IPG strips of pH 4-7. Among the 102 protein spots processed, 87 spots representing 77 proteins were successfully identified. Some virulence-associated proteins of SS2 were found, including arginine deiminase, ornithine carbamoyl-transferase, carbamate kinase, muramidase-released protein precursor, extracellular factor, and suilysin. Enolase and endopeptidase have been proposed as putative virulence-associated factors in this study. The 2-D reference map might provide a powerful tool for analyzing the virulence factor and the regulatory network involved in the pathogenicity of this microorganism.