Establishment Of Spa-Agglutination Method For Serotyping Of Streptococcus Suis And Application In Epidemiological Survey

In this paper, a SPA-agglutination (SPA-COA) method was established for serotyping of Streptococcus suis with35reference strains. And it was applied to carry out epidemiological survey of Streptococcus suis in parts of China by combining with PCR and MLST typing method. The contents were as following:1. The preparimary establishment of Co-agglutination test for serotyping of Streptococcus suisAfter staphylococcus A protein (SPA) was sensitized with antibodies against35serotpyes strains of Streptococcus suis, a method of co-agglutination was established for serotyping of Streptococcus suis. The results showed that the work concentration of sensitized SPA is50%,30serotypes’ work concentrations ranged from25to26, Visible agglutination particles can be observed when the OD of concentration of antigen liquid culture is between0.55and1.0. The agglutination is more significant when the OD of concentration of antigen liquid culture is around0.7. Positive strains1,2,7,9which have been tested by PCR, were turned out to be still positive by SPA-COA test. Three groups control have no agglutination. Serotype31～34observed weaker agglutination, need to do further study. Antiserums which existence of cross-reactivity, obtained type-specific antiserum by cross-adsorption process, take on well agglutination with the corresponding serotype strains, can be used into clinical test.2. The epidemiological survey of Streptococcus suis in Parts of ChinaThe established SPA-COA method was applied to epidemiological survey. Sixteen isolates were detected from370samples which were come from parts of China, the apparent carrier rate being4.32%. SPA-COA test has the same serotypes with serotypel、2、7、9multiplex PCR, can distinguish the serotype1and14、2and1/2, which is cannot distinguish by PCR. SPA-COA was used to detect20strains of Streptococcus suis preserved in our laboratory. The results indicated that1strain belong to serotype1/2,4strains serotype2, which being identified with the results of serotype2PCR. It indicated that SPA-COA test has good specificity. Moreover, it was firstly found that there were3strains of serotype28Streptococcus suis and1strain of serotype29Streptococcus suis in China. The MLST results showed that two high pathogenic strains of serotype2isolated from the same area belong to ST1, one strain belong to a new ST type, which has been included by MLST database, named ST164.In summary, the established SPA co-agglutination method, combined with serotype PCR methods, can accurately distinguish between cross-agglutination reaction of the strains, make a clear serotyping for those PCR can not be serotyped strains.lt is better to understand the distribution and prevalence of Streptococcus suis, and provide a powerful tool in epidemiological surveys of Streptococcus suis, also a reference for the prevention and control of Streptococcus suis.