Practice Based Learning: Effects of Antibiotic Pretreatment on Culture Yield in Osteomyelitis

Sunita Hemani

 

 

 

 

Presented by Sunita Hemani MD (PGY3)

Clinical Question:

  • What is the impact of antibiotic pretreatment on bone culture yield in children with suspected osteomyelitis?

Diagnosis of Osteomyelitis:

  • Hallmark Signs:
    • Localized bone pain + Limited joint motion
  • Variable Factors:
    • Presentation:
      • +/- Fever
      • +/- Reactive Effusion and/or Erythema
    • Labs:
      • +/- Leukocytosis
      • +/- Elevated CRP/ESR
      • +/- Positive Blood Culture
  • Imaging:
    • X-Ray – initial imaging usually
    • MRI – imaging of choice
  • Definitive Diagnosis:
    • Aspiration of the metaphysis or subperiosteal pus for pathogen identification via gram stain & culture

Empiric Antibiotics in Osteomyelitis:

  • Dilemma:
    • Many treatment guidelines (i.e. IDSA, AAFP, etc) recommend starting empiric antibiotics AFTER obtaining bone cultures
      • Afraid likelihood of (+) cultures will be reduced
  • BUT, what if bone cultures cannot be obtained until the following day or after a weekend?

 Conclusion of Zhorne, et al. (2015):

  • Bone biopsy results NOT affected by previous antibiotic administration
    • Possible Bias? … Greater disease severity or bacterial load for pretreated group
    • Bacteremia more common in pre-treated groups (OR 7, 95% CI 2.1-24.1)
    • Elevated WBC and CRP & MRI joint effusion more common in pretreated groups
  • BUT, longer duration of antibiotic therapy before bone biopsy was associated with lower culture yield
  • Only bone biopsy positive for 1/3 of the children
    • Takes longer to sterilize bone than blood?
    • Makes bone biopsy/culture crucial in diagnosing AHO

Study limitations of Zhorne, et al. (2015):

  • Small sample size
  • Not a randomized study
  • Selection Bias:
    • Children who received vs did not receive antibiotics before biopsy
    • The selection of antibiotics administered
    • Variation in illness severity
  • Indication for bone biopsy not always evident in medical record

Clinical Takeaway:

  • Empiric antibiotics should be initiated in all patients with suspected osteomyelitis … even if cultures cannot be obtained prior to antibiotic initiation

References:

Conrad DA. Acute hematogenous osteomyelitis. Pediatr Rev. 2010 Nov;31(11):464-71.

Wolf M. Knee Pain in Children, Part II: Limb- and Life-threatening Conditions, Hip Pathology, and Effusion. Pediatr Rev. 2016 Feb;37(2):72-6; quiz 77.

McNeil JC, et al. Role of Operative or Interventional Radiology-Guided Cultures for Osteomyelitis. Pediatrics. 2016 May;137(5).

Zhorne DJ, et al. Impact of antibiotic pretreatment on bone biopsy yield for children with acute hematogenous osteomyelitis. Hosp Pediatr. 2015 Jun;5(6):337-41.

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