| Staphylococcus aureus or coagulasenegative (methicillin-sensitive) Staphylococci | Nafcillin (Unipen), 2 g IV every 6 hours, or clindamycin phosphate (Cleocin Phosphate), 900 mg IV every 8 hours | First-generation cephalosporin or vancomycin (Vancocin) |
| S. aureus or coagulase-negative (methicillin-resistant) staphylococci | Vancomycin, 1 g IV every 12 hours | Teicoplanin (Targocid),* trimethoprim- sulfamethoxazole (Bactrim, Septra) or minocycline (Minocin) plus rifampin (Rifadin) |
| Various streptococci (groups A and B β-hemolytic organisms or penicillin-sensitive Streptococcus pneumoniae) | Penicillin G, 4 million units IV every 6 hours | Clindamycin, erythromycin, vancomycin or ceftriaxone (Rocephin) |
| Intermediate penicillin-resistant S. pneumoniae | Cefotaxime (Claforan), 1 g IV every 6 hours, or ceftriaxone, 2 g IV once daily | Erythromycin or clindamycin |
| Penicillin-resistant S. pneumoniae | Vancomycin, 1 g IV every 12 hours | Levofloxacin (Levaquin) |
| Enterococcus species | Ampicillin, 1 g IV every 6 hours, or vancomycin, 1 g IV every 12 hours | Ampicillin-sulbactam (Unasyn) |
| Enteric gram-negative rods | Fluoroquinolone (e.g., ciprofloxacin [Cipro], 750 mg orally every 12 hours) | Third-generation cephalosporin |
| Serratia species or Pseudomonas aeruginosa | Ceftazidime (Fortaz), 2 g IV every 8 hours (with an aminoglycoside given IV once daily or in multiple doses for at least the first 2 weeks) | Imipenem (Primaxin I.V.), piperacillin-tazobactam (Zosyn) or cefepime (Maxipime; given with an aminoglycoside) |
| Anaerobes | Clindamycin, 600 mg IV or orally every 6 hours | For gram-negative anaerobes: amoxicillin-clavulanate (Augmentin) or metronidazole (Flagyl) |
| Mixed aerobic and anaerobic Organisms | Amoxicillin-clavulanate, 875 mg and 125 mg, respectively, orally every 12 hours | Imipenem |