If nongonococcal gram-positive infection is suspected by Gram stain in an adult, or if no organisms are seen, treatment is with: A semisynthetic penicillin (eg, nafcillin 2 g IV every 4 hours) A cephalosporin (eg, cefazolin 2 g IV every 8 hours) Vancomycin 1 g IV every 12 hours However, because methicillin resistance is now common in community-acquired S aureus, for patients with gram-positive cocci in clusters on gram stain or a negative gram stain when S aureus is suspected, vancomycin is the empiric choice.