Current News
05 June 2008International Journal of Medical Microbiology
Multiplex PCR for the detection of Streptococcus pyogenes-superantigens
A new multiplex real-time PCR identifies eleven different superantigens of Streptococcus pyogenes at a time and thus provides and excellent tool in clinical diagnosis. Scientists from Germany and Jordan describe the PCR method which is based on the use of two different primer mixes in the „International Journal of Medical Microbiology“. Analysing more than 300 clinical S. pyogenes isolates, they found one strain without any superantigen (SAg), contradicting previous reports that identified SAgs on every strain examined. Perhaps „clinical isolates from patients (...) overrepresent bacterial strains with pathogenic factors, such as SAgs“, they conclude.
S. pyogenes is one of the most common pathogenic bacteria in human and causes several diseases, such as sinusitis, pneumonia, scarlet fever or necrotizing fasciitis and toxic shock syndrome. Several lines of evidence indicate that SAgs are involved in pathogenesis. These bacterial toxins bypass normal intracellular antigen processing and presentation by the major histocompatibility complex (MHC) class II. They elicit a massive secretion of inflammatory toxins and thereby induce severe tissue damage, organ failure, and shock.
Thus far, eleven SAgs from S. pyogenes are recognized named SPEA, SPEC, SPEG, SPEH, SPEI, SPEJ, SPEK, SPEL, SPEM, SSA and SMEZ. Maria Lintges of the Institute of Immunology at RWTH Aachen University Hospital et al. now developed a closed-tube multiplex real-time PCR for the identification of these SAgs. They evaluated the new method using clinical S. pyogenes isolates. With two primer mixes and SYBR-Green dye they were able to immediately detect the presence of all eleven SAg genes. One strain did not contain any of the SAgs tested.
„With our method, immediate information can be obtained wether or not a strain contains SAg gene“, the scientists write. „Additionally this closed system is free of any post PCR contamination so that one potential source of error could be eliminated.“ They further note, that their fast screening method can be used to identify SAg gene-less strains thereby helping to clarify the role of SAgs in S. pyogenes infections.
A new closed-tube multiplex real-time PCR to detect eleven superantigens of Streptococcus pyogenes identifies a strain without superantigen activity. Maria Lintges et al., International Journal of Medical Microbiology, Vol. 297, pp. 471-478.
