Underimmunized / special exposures (Haemophilus influenzae type b (if underimmunized) · Salmonella (hemoglobinopathy) · gram-negatives (immunocompromised))
First-line therapy
Cefazolin • i.v. • 33–33 mg/kg/dose • 3×/day
Max 2000 mg/dose · Max 6000 mg/day · Duration: 3–4 weeks · IV until clinical improvement (often 2–4 days) then oral step-down; total 2–3 weeks for uncomplicated/Kingella and 3–4 weeks for S. aureus (ID/ortho-guided)
• Obtain joint aspiration (synovial fluid Gram stain/culture ± PCR) before antibiotics when feasible; do not delay antibiotics in unstable/septic child.
• Obtain blood cultures before antibiotics when feasible (bacteremia is common with S. aureus).
• Urgent surgical drainage indicated with hip involvement, large purulent effusion, neurovascular compromise, or poor clinical response after 24–48 h of appropriate antibiotics.
• IV→PO switch when afebrile, pain and range of motion improving, hemodynamically stable, tolerating oral therapy, and CRP is clearly down-trending.
• Follow-up: reassess clinically and with CRP (± ESR) within 48–72 h; early orthopedic consult for any suspected septic arthritis.
Enter weight on Kids to calculate doses
Cefuroxime • i.v. • 50–50 mg/kg/dose • 3×/day
Max 1500 mg/dose · Duration: 3–4 weeks · Alternative beta-lactam with activity vs Kingella and streptococci; adjust to local susceptibility patterns
• Cefuroxime: suspected Kingella kingae (preschool) when cefazolin not suitable and local susceptibility supports; ensure culture/PCR when available.
• Cephalexin step-down: culture-confirmed MSSA or streptococci with good clinical response to IV therapy.
• Clindamycin step-down: clindamycin-susceptible MRSA (including negative D-test) or beta-lactam allergy; avoid if inducible resistance suspected.
• Adolescents with possible gonococcal arthritis: obtain NAAT from genital/pharyngeal sites and treat per gonorrhea guidance (not covered by standard pediatric empiric regimens).
• Neonates (<3 months), immunocompromised, sickle cell disease, penetrating trauma, or healthcare-associated infection: broaden workup and involve ID/orthopedics early; standard regimens may be inadequate.
Enter weight on Kids to calculate doses
Clinical notes
• Diagnostics before antibiotics when feasible: joint aspiration for synovial WBC, Gram stain/culture ± PCR (Kingella PCR in preschool), and blood cultures; do not delay antibiotics in unstable child.
• Urgent orthopedic consult and drainage: hip septic arthritis, large effusion/pus, neurovascular compromise, or failure to improve within 24–48 h of appropriate antibiotics; repeat aspiration/drainage may be needed.
• MRSA considerations: add MRSA-active agent (clindamycin if susceptible and child stable; vancomycin if severe illness, bacteremia, or high clindamycin resistance) based on local epidemiology.
• IV→PO switch criteria: improving pain and range of motion, afebrile and clinically stable, tolerating oral medications, reliable follow-up, and CRP clearly down-trending; reassess in 48–72 h after switch.
• Duration and follow-up: total 2–3 weeks for uncomplicated cases (especially Kingella) and typically 3–4 weeks for S. aureus; monitor clinical response and CRP until normalization or clear downward trend.
