What is the next step in treating a persistent abscess that has not responded to treatment with cephalexin (Cefalexin) and Bactrim (Trimethoprim/Sulfamethoxazole)?

Management of Persistent Abscess After Failed Cephalexin and Bactrim Treatment

The most critical next step is to perform incision and drainage if an abscess is present, as antibiotics alone will fail without adequate source control, and obtain wound cultures to guide targeted antibiotic therapy. 1

Immediate Surgical Intervention

Incision and drainage is the primary treatment for abscess—antibiotics are only adjunctive. 1, 2 The recurrence after initial response to cephalexin strongly suggests either inadequate drainage or the presence of MRSA that is not covered by cephalexin alone. 1

• Perform incision and drainage immediately if any purulent collection or abscess is present, as antibiotics without drainage have poor outcomes. 1, 3
• Consider removing any foreign material (such as piercing jewelry if applicable), as foreign bodies perpetuate infection and cause recurrent abscess formation. 1
• Patients requiring surgical intervention more than 24 hours after antibiotic initiation should be considered treatment failures. 4

Culture-Directed Approach

Obtain wound culture before starting new antibiotics to identify the causative pathogen and guide targeted therapy. 1 The failure to respond to both cephalexin (which covers methicillin-sensitive Staphylococcus aureus and streptococci) and Bactrim (which covers MRSA) suggests either:

• Inadequate source control (undrained abscess)
• Resistant organism
• Polymicrobial infection including anaerobes (Bactrim has poor anaerobic coverage) 2

Antibiotic Selection for Persistent Infection

Since the abscess has failed both cephalexin and Bactrim, switch to a different MRSA-active agent while awaiting culture results:

First-Line Options:

• Clindamycin 300-450 mg four times daily for 5-10 days 1, 2
  • Provides excellent MRSA coverage
  • Also covers anaerobes (unlike Bactrim)
  • Particularly useful for polymicrobial infections

Alternative Options:

• Doxycycline 100 mg twice daily for 5-10 days 1, 2
• Continue trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily ONLY if drainage is performed 1, 2

When Standard Therapy Fails:

If multiple antibiotic courses have failed despite adequate drainage, consider:

• Consultation with infectious disease specialist before using unconventional agents 5
• Levofloxacin (not FDA-approved for skin infections in children but effective against resistant organisms) 5
• Linezolid (expensive, effective against multidrug-resistant Gram-positive bacteria) 5

Treatment Duration and Monitoring

• Treat for 5-10 days after obtaining cultures and performing drainage 1
• Extend duration if no improvement within 5 days 1
• Reassess within 24-48 hours to ensure clinical improvement 1
• If worsening or no improvement occurs, consider hospitalization for IV vancomycin 15-20 mg/kg every 8-12 hours 1

Decolonization to Prevent Recurrence

Implement a 5-day decolonization regimen including: 1

• Intranasal mupirocin twice daily
• Daily chlorhexidine body washes
• Daily decontamination of personal items (towels, bedding, clothing)

Alternative decolonization strategies with stronger evidence:

• Nasal mupirocin twice daily for the first 5 days of each month reduces recurrences by ~50% 2
• Clindamycin 150 mg daily for 3 months is superior, reducing recurrences by ~80% 2

Critical Pitfalls to Avoid

• Do NOT continue cephalexin—the recurrence indicates treatment failure, likely due to MRSA or inadequate drainage 1
• Do NOT rely on antibiotics alone if an abscess is present—surgical drainage is essential 1, 3
• Do NOT use Bactrim alone for cellulitis without purulent drainage, as it has poor activity against Group A Streptococcus 6, 2
• Do NOT assume the infection will resolve with the same antibiotic—recurrence at the same site requires culture-directed therapy and investigation for local factors 1

When to Escalate Care

Consider hospitalization and IV antibiotics if: 1

• No improvement after 48-72 hours of appropriate oral therapy with adequate drainage
• Systemic signs of infection (fever, hypotension, altered mental status)
• Rapidly spreading infection
• Immunocompromised patient
• Concern for deeper infection (necrotizing fasciitis, osteomyelitis)

Adjust antibiotics based on culture results when available to narrow spectrum and optimize therapy. 1