Background. In this study, we examined the role of superantigen genes and emm genotypes of clinical Streptococcus pyogenes isolates collected in Germany between 1997 and 2003.

Methods. Multiplex polymerase chain reaction for all 11 currently known superantigen genes and sequencing for emm types were used.

Results. Using a 2-step explorative data analysis procedure, we found that after combined analysis of superantigen genes and emm types, only the superantigen genes spea1-spea3, spem, and spea4 have a predictive value for invasiveness, with odds ratios of 7.992, 3.209, and 2.323, respectively. The predictive value for invasiveness of emm1 was lost after combined analysis because of the association between emm type and the highly predictive superantigen genes. On the other hand, presence of the superantigen gene ssa and of emm77 are predictors of noninvasiveness, with odds ratios of 0.370 and 0.271, respectively.

Conclusions. These results indicate that the presence of superantigen genes is more important for the invasiveness of group A Streptococcus infection than emm type and may be the connection between the high-risk HLA type of the host and the pathogen. Furthermore, we found a very clear correlation between the presence of the genes spea1-spea3 and the presence of the gene emm1, which indicates that the relationship between emm1 and invasiveness is based on the superantigen gene profile. Our data suggest that the superantigen gene profile is of high importance for the clinical outcome of group A Streptococcus infections.