Development of a Real-Time PCR Assay for the Detection and Diagnosis of Streptococcus suis in Clinical Samples

Abstract

<p>Streptococcus suis is an important pathogenic bacteria known to cause meningitis and fibrinous polyserositis in swine. Several bacterial real-time polymerase chain reaction assays (qPCRs) have been developed for use at the Iowa State University Veterinary Diagnostic Laboratory (ISU VDL); however, qPCR protocols for the detection of S. suis were lacking. qPCR is often considered an appealing alternative to culture-based or immunoassay-based diagnostic methods because of its ability to rapidly test a large volume of samples with a high degree of target specificity. One hundred seventy-four clinical samples were obtained from the ISU VDL and were tested by qPCR targeting the recombination/repair protein (recN) gene. Samples were collected both prospectively and retrospectively. Ninety-three BacT positive samples were analyzed across sample type (brain, lung, heart, joint fluid). A Pearson χ2 value of 4.024 and a P-value of 0.1337 suggests anatomical location does not affect testing outcome when α=0.05. The data were then aggregated based on case level and compared to the case diagnosis. Using this method, a qPCR positive result agreed with a diagnosis of S. suis 59.7±10.3% of the time, while the isolation of S. suis agreed with a diagnosis of infection in 75±8.2% of diagnostic cases.</p>