FIG. 1.

The adhesin FnBP confers invasiveness to an FnBP-deficient, noninvasive S. aureus mutant. Overexpression (+++) of adhesins in strain DU5883 by multicopy plasmids was tested for invasion of 293 cells. Strain DU5883 (an FnBPA- and FnBPB-deficient isogenic mutant of 8325-4) served as a parental strain to provide an S. aureus background completely devoid of FnBPs. (A) Total internalized bacteria were measured by lysostaphin (20 μg/ml) protection. Results are means and SEMs for four independent experiments run in duplicate and are expressed as recovered CFU, normalized for the actual inoculum. (B) Total internalized bacteria were measured by flow cytometry with fixed bacteria. Results are means and SEMs for three independent experiments run in duplicate and are expressed as invasiveness relative to that of strain Cowan 1. AFU, arbitrary fluorescence units.