FIG 3.

SLO and capsule contribute to GAS resistance to killing by neutrophils after LL-37 exposure or inactivation of csrR. GAS strains were grown in the absence or presence of 300 nM LL-37 prior to exposure to human neutrophils. CFU were determined by quantitative cultures at the beginning and end of a 1-h incubation and are plotted as percent survival, i.e., number of CFU at 1 h expressed as a percentage of the number present at the beginning of the experiment. (A) Infections with GAS 854, 854Δslo, 854ΔhasB, and 854ΔhasB/Δslo; (B) those with 854ΔcsrR, 854ΔcsrR/Δslo, 854ΔcsrR/ΔhasB, and 854ΔcsrR/ΔhasB/Δslo. Data are means and SEM from four independent experiments; each experiment assayed each condition in duplicate. Asterisks indicate significant differences from parental strain 854 or 854ΔcsrR for the same condition: *, P < 0.05; **, P < 0.01; ***, P < 0.001. NS, not significant.