FIG. 2.
The M. catarrhalis adhesin UspA1 was necessary for enhanced adherence to Chang cells. S. pyogenes (∼2 × 107 CFU) and M. catarrhalis (∼2 × 107 CFU) were incubated with Chang cells either alone or mixed as described in Materials and Methods. Results represent the mean of two to four independent experiments done in duplicate. Error bars represent the standard deviations. (A) The adherence of a uspA1 mutant of M. catarrhalis to Chang cells (open bar) was only 10% of that of the isogenic wild-type strain (gray bar), as previously reported (1). Coinfection with S. pyogenes had a small effect on the adherence of the M. catarrhalis uspA1 mutant (closed bar). (B) Wild-type M. catarrhalis enhanced the adherence of S. pyogenes 18-fold (gray bar versus open bar). The M. catarrhalis uspA1 mutant enhanced the adherence of S. pyogenes only twofold (closed bar).