Fig 1. Selection of SpeB^A- variants of SpeB^A+ invasive emm1 isolates in subcutaneous infection of mice.

Five or 10 mice were subcutaneously inoculated with ~10⁸ cfu of each of the indicated 24 emm1 invasive isolates. Four days later, GAS bacteria were recovered from skin infection sites, and 48 colonies from each mouse were tested for SpeB activity in overnight culture supernatant by the casein hydrolysis assay. Presented are percentages of variants without detectable SpeB activity among the 48 colonies.