FIG 3.

Repair of the hasA mutation in strain MGAS12503 restores capsule production and virulence. (A) Hyaluronic acid assays of MGAS12503 and repaired strain MGAS12503hasA^wt. Error bars represent standard deviations after performing assays on three biologic replicate samples. Strain MGAS12503 did not produce detectable hyaluronic acid. fg, femtograms. (B) Survival curve of mice infected with MGAS12503 or repaired strain MGAS12503hasA^wt. Ten mice in each group were infected intramuscularly with 1 × 10⁷ CFU, as described in Materials and Methods. P values determined by log rank test. (C and D) Mice infected with MGAS12503hasA^wt had significantly greater myonecrosis at the site of infection than mice infected with MGAS12503 containing the mutant hasA allele. (E and F) Extensive tissue destruction (boxed area) and nonviable cells were observed in the mouse infected with strain MGAS12503hasA^wt, whereas animals infected with MGAS12503 had only small abscesses (black arrows). (G) Multiplication of MGAS12503 and MGAS12503hasA^wt in human blood. Whole blood was inoculated with the indicated strains as described in Materials and Methods. Shown is multiplication after growth in blood from a single donor. Similar results were obtained with additional donors. Error bars indicate standard deviations of growth performed in triplicate. P values were determined by t test (unequal variance).