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For further information, see CMDT Part 33-04: Staphylococcus aureus Infections

Key Features

  • S aureus is the cause of approximately 60% of all cases of osteomyelitis

  • Osteomyelitis may occur by

    • Direct inoculation (eg, from an open fracture or as a result of surgery or other procedure)

    • Extension from a contiguous focus of infection or open wound

    • Hematogenous spread (more common)

Clinical Findings

  • Acute, abrupt local symptoms and systemic toxicity; or insidious onset of vague pain over the site of infection, progressing to local tenderness and constitutional symptoms (fever, malaise, anorexia, night sweats)

  • Fever is absent in one-third or more of cases

  • Back pain

    • Often the only symptom in vertebral osteomyelitis

    • May be associated with an epidural abscess and spinal cord compression


  • Isolation of S aureus from the blood (60%), bone, or a contiguous focus of a patient with symptoms and signs of focal bone infection

  • Bone biopsy and culture should be considered if blood cultures are sterile

  • Inflammatory markers (C-reactive protein, erythrocyte sedimentation rare) are typically elevated

  • Bone scan and gallium scan can identify the site of bone infection

  • Spinal infection (unlike malignancy) traverses the disk space to involve the contiguous vertebral body

  • MRI

    • Slightly less sensitive than bone scan but has a specificity of 90%

    • Indicated when epidural abscess is suspected in association with vertebral osteomyelitis

  • 18F-FDG-PET/CT may be useful in the diagnosis of vertebral osteomyelitis as well as the detection of other metastatic sites of infection


  • Recommended antibiotic duration is 4–6 weeks or longer

  • For infection with methicillin-sensitive S aureus isolates, first-line intravenous regimens include

    • Cefazolin, 2 g every 8 hours or

    • Nafcillin or oxacillin, 9–12 g/day in six divided doses

  • For infection with methicillin-resistant S aureus isolates or for patients who have severe penicillin allergies

    • Vancomycin, 30 mg/kg/day intravenously divided in two or three doses

    • Doses should be adjusted to achieve a vancomycin trough level of 15–20 mcg/mL

  • For patients with S aureus isolates susceptible to oral agents, combination oral therapy has been shown to be effective if given for 4–6 weeks following 2 weeks of induction therapy with an intravenous agent

    • Levofloxacin (750 mg orally daily) or ciprofloxacin (750 mg orally twice daily) in combination with rifampin (300 mg twice daily) is an oral regimen with the most data supporting efficacy

    • Trimethoprim-sulfamethoxazole, doxycycline, or clindamycin may be an option for oral therapy

  • The role of newer agents, daptomycin or linezolid, remains to be defined

  • Surgical treatment is often indicated under the following circumstances:

    • Staphylococcal osteomyelitis with associated epidural abscess and spinal cord compression

    • Other abscesses (psoas, paraspinal)

    • Extensive disease

    • Recurrent or persistent infection despite standard medical therapy

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