Genetic diversity in T1M1 group A streptococci in relation to clinical outcome of infection.

Genetic diversity was found at high frequency downstream of the emm1 gene among T1M1 group A streptococci (GAS) isolated in Scandinavia during a recent epidemic. Clonal variation was also seen in the speA and speB genes but at much lower frequency; no variation was detected in the speC gene. Erythrogenic toxin A was found to be expressed at low levels in all strains; erythrogenic toxins B and C were produced in high amounts. All strains were found to harbor the speA, speB, and speC genes, regardless of the amount of toxin produced. No correlation was found between one specific T1M1 clone and the more serious infections when isolates from bacteremic patients (fatalities or survivors), those with uncomplicated infections, and healthy carriers were compared. Similar results were obtained in a family study in which 3 family members were found to be asymptomatic carriers of the same GAS T1M1 clone as in the bacteremic patient, defined by genotypic and phenotypic experiments.