Growth curves of S. aureus strains MRSA 10 (a) and MRSA21 (b) treated with or without azithromycin. (black rhombus), untreated S. aureus; (black square), S. aureus plus azithromycin at 1/2 MIC; (black triangle), S. aureus plus azithromycin at 1/4 MIC; (*), S. aureus plus azithromycin at 1/8 μg/mL; and (black circle), S. aureus plus azithromycin at 1/16 μg/mL