We studied 83 cardiac-surgery patients with nasal S. aureus carriage who received 4 intranasal administrations of XF-73 nasal gel or placebo <24 hours before surgery. One hour before surgery, patients exhibited a S. aureus nasal carriage reduction of 2.5 log10 with XF-73 compared to 0.4 log10 CFU/mL for those who received placebo (95% CI, -2.7 to -1.5; P < .0001).