Chapter 120. Osteomyelitis (Part 5) Table 120- 2 Selection of Antibiotics for Treatment of Acute Osteomyelitis Suggested Regimen a Organism Primary Alternatives b Staphylococcus aureus Penicillin- Nafc illin or oxacillin, 2 g Cefazolin, 1 g IV resistant, methicillin- sensitive (MSSA) IV q4h q8h; ceftriaxone, 1 g IV q24h; clindamycin, 900 mg IV q8h c Penicillin- sensitive Penicillin, 3– 4 million U IV q4h Cefazolin, ceftriaxone, clindamycin (as above) Methicillin- resistant (MRSA) Vancomycin , 15 mg/kg IV q12h; rifampin, 300 mg PO q12h (see text) Clindamycin c (as above); linezolid, 600 mg IV or PO q12h d ; daptomycin, 4– 6 mg/kg IV q24h d Streptococci (including S. milleri, b- hemolytic streptococci) Penicillin (as above) Cefazolin, ceftriaxone , clindamycin (as above) Gram-negative aerobic bacilli Escherichia coli , other "sensitive" species Ampicillin, 2 g IV q4h; cefazolin, 1 g IV q8h Ceftriaxone, 1 g IV q24h; parenteral or oral fluoroquinolone (e.g., ciprofloxacin, 400 mg IV or 750 mg PO q12h) e Pseudomonas aeruginosa Extended-spectrum b- lactam agent (e.g., piperacillin, 3–4 g IV q4– 6h; or ceftazidime, 2 g IV q12h) plus tobramycin, 5–7 mg/kg q24h f May substitute parenteral or oral fluoroquinolone for b- lactam agents (if patient is allergic) or for tobramycin (in relation to nephrotoxicity) Enterobacter Extended-spectrum b- spp., other "resistant" species lactam agent IV or fluoroquinolone IV or PO e (as above) Mixed infections possibly involving anaerobic bacteria Ampicillin/sulbactam, 1.5– 3 g IV q6h; piperacillin/tazobactam, 3.375 g IV q6h Carbapenem antibiotic or a combination of a fluoroquinolone plus clindamycin (as above) or metronidazole, 500 mg PO tid a Duration of treatment is discussed in the text. b Cephalosporins m ay be used for the treatment of patients allergic to penicillin whose reaction did not consist of anaphylaxis or urticaria (immediate- type hypersensitivity). c Because of the possibility of inducible resistance, clindamycin must be used with caution for the treatment of strains resistant to erythromycin. Consult clinical microbiology laboratory. d Experience is limited; there are anecdotal reports of efficacy. e Oral fluoroquinolones must not be coadministered with divalent cations (calcium, magnesium, iron, aluminum), which block the drugs' absorption. f Tobramycin levels and renal function must be monitored closely to minimize the risks of nephro- and ototoxicity. . Chapter 120. Osteomyelitis (Part 5) Table 120- 2 Selection of Antibiotics for Treatment of Acute Osteomyelitis Suggested Regimen a Organism