FIG. 6.

Adherence of isogenic M1 GAS strains to cultured human epithelial cells. Mid-log phase cultures of the wild-type strains (open bars) and scl-inactivated mutants (filled bars) were incubated with A549 epithelial cells for 1 h. Unattached bacteria were removed by washing. The attached GAS were stained and counted microscopically. The results are presented as mean numbers of GAS cells attached to each A549 cell ± standard error of the mean (error bars). The difference in adherence between the wild type and mutant derivatives was significant by t test for both MGAS 5005 and MGAS 6708 strain pairs.