Development and application of multiplex PCR assay for rapid detection of Streptococcus suis species and its main pathogenic serotypes 1, 2 and 7.

【Objective】The study was done to develop rapid and specific multiplex PCR assay for detection of Streptococcus suis(S.suis)and its main pathogenic serotypes 1(and 14),2(and 1/2)and 7.【Method】Four pairs of primers were designed in this multiplex PCR assay,which was based on the sequences of the species-specific gene coding for glutamate hydrogenase(gdh)of S.suis and serotypes-specific genes of cps 1 I,cps 2 Hand cps7 Hcoding for the capsule of S.suis serotypes 1(and 14),2(and 1/2)and 7,respectively.By optimizing the single and multiplex PCR conditions and primers concentrations,a stable multiplex PCR assay was established.To evaluate the specificity,strains of other bacterial species related to S.suis or isolated from pigs were analyzed.The multiplex PCR assay was then applied to the detection of 39 tonsils,and several PCR products were sequenced to confirm the PCR assay.【Result】The PCR assay was rapid,exact,specific and sensitive.When genomic DNA of S.suis serotype 2 was used as template for PCR,the detection threshold of the test was 2.52 CFU per assay.【Conclusion】The multiplex PCR assay can be applied in rapid detection of S.suis and its main pathogenic serotypes from tonsils.