Multiplex PCR Assay for Detection of Streptococcus suisSpecies and Serotypes 2 and 1/2 in Tonsils of Live and Dead Pigs

ABSTRACTA PCR assay was developed for the detection of Streptococcus suisserotypes 2 and 1/2. This multiplex PCR is based on the amplification of the gene coding for 16S rRNA of S. suisand on the amplification of the cps2Jgene coding for the capsule of S. suisserotypes 2 and 1/2. An internal control was constructed and added in this test to monitor the efficiency of amplification in each reaction. To evaluate the specificity of the test, 31 strains of other bacterial species related to S. suisor isolated from pigs and 42 strains of S. suisserotypes 1 and 3 to 34 were analyzed. The detection threshold of the test was 28 S. suisCFU/ml. The specificity and the sensitivity of the multiplex PCR test and the presence of an internal control allowed the analysis of biological samples without a culture step. The PCR assay was then applied to the detection of 14 S. suisserotype 1/2 strains, 88 S. suisserotype 2 strains isolated from pigs, and 25 S. suisserotype 2 strains isolated from humans. This test was also applied to analyze tonsil samples of pigs experimentally infected and carrier pigs without any symptoms.