First results of multilocus sequence typing (MLST) for characterization of 29 invasive Streptococcus pyogenes strains isolated in the Czech Republic in the first half of 2003 are presented. None of 16 emm types detected among the study strains showed sequence type (ST) variability. The MLST results are indicative of differences between the strains causing serious diseases in the Czech Republic and those isolated in other countries. In seven strains, four new STs with known alleles in new combinations, ST134, ST308, ST336, ST340, and one new ST with three as yet undescribed alleles (gki 91, murI 65 and yqiL 60), ST341, were described. These newly described STs were submitted to the web-based reference MLST database for S. pyogenes.

        Key words: invasive group A streptococci – clonal analysis – MLST – streptococcus.