How should I manage a 56‑year‑old man with a progressive back abscess that is not improving on oral clindamycin?

Management of Progressive Back Abscess Failing Oral Clindamycin

This patient requires immediate hospitalization for surgical drainage and intravenous antibiotics, as failure to respond to oral clindamycin after a reasonable trial indicates either inadequate source control, resistant organisms, or a more serious infection such as necrotizing fasciitis or deep-seated abscess.

Immediate Actions Required

Hospitalization and Surgical Evaluation

• Failure of apparently uncomplicated cellulitis or abscess to respond to antibiotics after a reasonable trial is a red flag for necrotizing fasciitis or inadequate drainage 1
• Surgical intervention is the primary therapeutic modality and should be pursued urgently when infection progresses despite appropriate antibiotics 1
• Early drainage of purulent material must be performed, as source control is often the primary reason for treatment failure rather than antibiotic choice alone 1, 2

Imaging Studies

• Obtain MRI of the spine to rule out deeper infection including epidural abscess, pyomyositis, or vertebral osteomyelitis, which can present as progressive back abscess 1, 3
• CT scan or ultrasound are also useful if MRI is unavailable 1

Antibiotic Management

Switch to Intravenous Therapy

• Initiate vancomycin 15-20 mg/kg IV every 8-12 hours as empiric therapy for MRSA coverage 1
• Add clindamycin 900 mg IV every 8 hours to provide anaerobic coverage and toxin suppression 1, 2, 4
• The combination of vancomycin plus clindamycin has been shown to decrease hospital length of stay by 18.2% in patients with abscesses and reduce 90-day readmission rates from 24.3% to 2.0% 4

Why Oral Clindamycin Failed

Several critical factors explain treatment failure:

• Inadequate source control: Abscesses require drainage; antibiotics alone are insufficient for most cases 1
• Possible MRSA with inducible clindamycin resistance: The presence of inducible resistance should preclude clindamycin use for serious infections 1
• Deeper infection: Back location raises concern for spinal epidural abscess, pyomyositis, or vertebral osteomyelitis requiring IV therapy 1, 3

Obtain Cultures

• Blood cultures must be obtained before starting IV antibiotics 1
• Culture abscess material during drainage 1
• Repeat imaging should be performed if bacteremia persists to identify undrained foci 1

Duration of Therapy

• Antibiotics should be administered intravenously initially, transitioning to oral once clinically improved 1
• If no improvement occurs within 72 hours of IV antibiotics plus drainage, repeat imaging is mandatory to identify undrained collections 1, 2
• For uncomplicated abscess after drainage: 2-3 weeks total therapy 1
• For complicated infections (osteomyelitis, epidural abscess): 6 weeks or longer may be required 3

Critical Pitfalls to Avoid

• Do not continue oral antibiotics when a patient is failing therapy: This delays definitive treatment and risks progression to sepsis or necrotizing infection 1
• Do not assume simple cellulitis: Progressive infection on antibiotics suggests abscess, necrotizing fasciitis, or deep-seated infection requiring imaging 1
• Do not rely on antibiotics alone without drainage: Source control is paramount for abscess treatment 1, 2
• Do not use clindamycin monotherapy for serious MRSA infections if inducible resistance is present: Vancomycin should be the backbone of therapy 1