a,b, Keratinocytes were infected (MOI=100) with GAS 5448, isogenic mutant controls, or clinical isolates for 4 h and (a) lysis measured by LDH release and (b) SpeB activity measured using specific substrate Mca-IFFDTWDNE-Lys-Dnp. c, GAS labeled with Bocillin was incubated with keratinocytes (MOI=100) 1 h, washed, and adherence measured by fluorescence. Data are representative of three independent experiments with 3 technical replicates and are presented as the mean±s.d. P values were calculated by two-way ANOVA compared to 5448 (M1) control; P<0.0001.