Multiplex PCR for identification of six clinically relevant streptococci

Purpose. The aim of this study was to develop a multiplex PCR (mPCR) for simultaneous detection (single reaction) of six clinically relevant streptococcal species: Streptococcus pneumoniae, Streptococcus suis, Streptococcus gallolyticus subsp. gallolyticus, S. gallolyticus subsp. pasteurianus, Streptococcus intermedius and Streptococcus anginosus/constellatus. Methods. mPCR with primers specific for S. pneumoniae (lytA), S. suis (recN), S. gallolyticus subsp. gallolyticus (tanB), S. gallolyticus subsp. pasteurianus (SGPB0680 cell wall surface protein), S. intermedius (ily) and S. anginosus/constellatus (moaC) was employed with 37 reference bacterial strains and 442 clinical streptococcal isolates collected from seven tertiary hospitals in north-east Thailand. Results from this mPCR were compared to those obtained with the API 20 Strep and conventional biochemical tests. Results. The six clinically relevant streptococcal species gave the expected amplification products of 229, 362, 531, 723, 819 and 978 bp for S. pneumoniae, S. gallolyticus subsp. gallolyticus, S. gallolyticus subsp. pasteurianus, S. suis, S. intermedius and S. anginosus/S. constellatus, respectively. Non-specific reactions were not observed with the other bacterial species tested. For the 442 clinical streptococci, this mPCR assay confirmed the identity of the species in accordance with results obtained with the API 20 Strep and conventional biochemical tests. Conclusion. This mPCR can be applied to the rapid identification of pure cultures of these six streptococci. The test was shown to be rapid, simple and reliable for the identification of these streptococci at the species level. This assay should be useful for laboratory identification and surveillance of human infections by these bacterial species.