Most common (Staphylococcus aureus (MSSA>MRSA depending on local epidemiology) · coagulase-negative staphylococci (esp. prior surgery/hardware) · streptococci)
Contiguous / polymicrobial contexts (Mixed flora possible with open fracture, penetrating trauma, pressure injury, or chronic draining sinus; consider gram-negatives and anaerobes based on exposure and operative findings)
First-line therapy
Cefazolin • i.v. • 33–33 mg/kg/dose • 3×/day
Max 2000 mg/dose · Max 6000 mg/day · Duration: Total ≥6 weeks (individualize) · Chronic osteomyelitis typically requires prolonged therapy after adequate source control; duration depends on debridement adequacy, organism, and response (ID/ortho-guided)
• Chronic differs from acute hematogenous osteomyelitis: often indolent with necrotic bone (sequestrum), sinus tract, and biofilm — antibiotics alone may fail without debridement/source control.
• Obtain deep bone/operative tissue cultures before antibiotics when feasible; do not use superficial swab cultures to guide therapy.
• Narrow therapy to culture and susceptibility as soon as possible; avoid prolonged broad empiric regimens.
• Consider MRSA coverage when risk factors or local prevalence warrant; de-escalate when cultures show MSSA or non-staphylococcal pathogens.
• Follow inflammatory markers (CRP ± ESR) and clinical status; imaging is for complications/poor response rather than routine 'test of cure'.
Enter weight on Kids to calculate doses
Clindamycin • i.v. • 10–10 mg/kg/dose • 3×/day
Max 600 mg/dose · Max 1800 mg/day · Duration: Total ≥6 weeks (individualize) · Use only if isolate is clindamycin-susceptible and D-test negative when applicable; consider local MRSA susceptibility
• Clindamycin: stable child with suspected CA-MRSA and high local susceptibility; confirm D-test when organism isolated.
• Vancomycin preferred: severe illness, bacteremia suspected/confirmed, prior MRSA colonization/infection, or high clindamycin resistance.
• Oral step-down is acceptable only with reliable adherence, improving pain/function, afebrile status, and clearly down-trending CRP.
• If hardware present or biofilm suspected, coordinate with orthopedics/ID for surgical strategy and antibiotic selection; narrow to culture results.
• If polymicrobial contamination suspected (e.g., open fracture), adjust empiric coverage beyond this pathway and tailor to intraoperative cultures.
Enter weight on Kids to calculate doses
Clinical notes
• Cultures first: obtain deep bone/operative tissue cultures (and blood cultures if febrile/systemic) before antibiotics when feasible; avoid superficial swab cultures from sinus tracts for definitive therapy decisions.
• Surgery/source control: chronic osteomyelitis commonly involves sequestrum/biofilm — surgical debridement (± hardware removal) is often required; antibiotics alone have higher relapse risk than acute hematogenous disease.
• Duration: typically ≥6 weeks total and may be longer if incomplete debridement, retained hardware, resistant organisms, or slow response; tailor to clinical course and source control rather than a fixed number of days.
• IV→PO switch: consider when pain/function improve, afebrile/hemodynamically stable, able to take/absorb oral meds, and CRP is down-trending; choose a high-bioavailability agent matched to susceptibilities.
• Follow-up: reassess clinically and with CRP/ESR; repeat imaging only when poor response, recurrent symptoms, suspected abscess/sequestrum progression, or to plan surgery (MRI/CT per ortho).
