FIG 4.
Capsule contributes to bacterial burden in mice but decreases ability to internalize epithelial cells. (A) Nasopharyngeal colonization of mice with GAS strains. Percent of colonized mice with >150 CFU isolated after daily swabbing for each strain: MGAS315 (invasive), MGAS12503 (carrier), and MGAS12503hasAwt (repaired carrier). Mice were inoculated intranasally and swabbed daily for 14 days as described in Materials and Methods. P values were determined by repeated-measures ANOVA. (B) Internalization of MGAS315, MGAS12503, and MGAS12503hasAwt into cultured human epithelial cells (HaCaT) as described in Materials and Methods. Less than 0.1% of strain MGAS315 internalized epithelial cells. P values are relative to the carrier strain MGAS12503 and determined by t test (unequal variance).