What is the treatment for a 7-year-old male (YOM) with culture-positive Cutibacterium (formerly Propionibacterium) acnes and inflamed prepatellar bursitis after a fall?

Treatment of Prepatellar Bursitis with Cutibacterium acnes in a 7-Year-Old Male

For a 7-year-old male with culture-positive Cutibacterium acnes prepatellar bursitis after a fall, treatment should include oral amoxicillin or cephalexin for 2-3 weeks, combined with local measures including aspiration, rest, and cold therapy.

Antibiotic Selection

The treatment approach for this case requires careful consideration of several factors:

1. Age-appropriate antibiotic selection:

   • Tetracycline-class antibiotics (doxycycline, minocycline) are first-line for Cutibacterium acnes infections in adults but are contraindicated in children under 8 years of age 1.
   • For children under 8 years, beta-lactams are appropriate alternatives:
     • Amoxicillin is effective against C. acnes and has been successfully used in pediatric bursitis cases 2.
     • Cephalexin is another appropriate option with activity against C. acnes 1, 3.

2. Antibiotic susceptibility:

   • C. acnes is generally susceptible to beta-lactams, clindamycin, and quinolones 4.
   • The FDA label confirms activity of clindamycin against C. acnes 3, but this should be reserved for patients with penicillin allergies due to increasing resistance concerns 4.

Treatment Protocol

Immediate Management

• Aspiration of the bursa to remove purulent material and reduce pressure 5, 6
• Culture and sensitivity testing (already completed in this case)
• Rest and elevation of the affected limb
• Cold therapy to reduce inflammation
• Consider immobilization if pain is severe

Antibiotic Therapy

• Primary option: Oral amoxicillin (40-50 mg/kg/day divided into 3 doses) for 2-3 weeks 2
• Alternative option: Oral cephalexin (25-50 mg/kg/day divided into 4 doses) for 2-3 weeks 1
• For penicillin-allergic patients: Oral clindamycin (10-30 mg/kg/day divided into 3-4 doses) 3

Follow-up Care

• Reassessment at 48-72 hours to ensure clinical improvement
• Complete the full course of antibiotics even if symptoms improve quickly
• Gradual return to activities as symptoms resolve
• Consider protective padding for the knee during recovery and future activities

Special Considerations

Monitoring for Complications

• Watch for signs of treatment failure including:
  • Persistent or worsening pain
  • Spreading erythema
  • Fever
  • Inability to bear weight on the affected leg

Prevention of Recurrence

• Protective padding for knees during sports and activities
• Proper technique for kneeling activities
• Prompt treatment of any skin injuries or abrasions

Rationale for Treatment Approach

This approach is based on several key considerations:

1. The patient's age (7 years) precludes the use of tetracyclines, which would typically be first-line for C. acnes in adults 1.

2. C. acnes is susceptible to beta-lactams, making amoxicillin or cephalexin appropriate choices 3, 4.

3. The traumatic origin (fall) suggests this is an acute septic bursitis rather than a chronic condition, requiring prompt antibiotic therapy to prevent progression to deeper structures 2, 5.

4. Septic bursitis in children is rare but can lead to serious complications including osteomyelitis if untreated 2.

5. Conservative measures including aspiration, rest, and cold therapy complement antibiotic therapy and help reduce inflammation and pain 5, 6.

The goal of treatment is to eradicate the infection, reduce inflammation, relieve pain, and prevent complications such as chronic bursitis or osteomyelitis, which could significantly impact the child's mobility and quality of life.