What antibiotic is used to treat an infected epidermoid cyst?

Management of Infected Epidermoid Cysts

Incision and drainage is the recommended treatment for infected epidermoid cysts, with antibiotics only necessary when there are signs of systemic inflammatory response syndrome (SIRS) or in patients with markedly impaired host defenses. 1, 2

Primary Treatment Approach

The Infectious Diseases Society of America (IDSA) provides clear guidelines for managing infected epidermoid cysts:

• First-line treatment: Incision and drainage is the definitive treatment for inflamed epidermoid cysts 1, 2
• Gram stain and culture: Not recommended for inflamed epidermoid cysts 1
• Post-procedure care: Cover the surgical site with a dry dressing 1, 2

Antibiotic Therapy Decision Algorithm

Antibiotics should be reserved for specific situations:

1. No antibiotics needed if:

   • Patient has no systemic symptoms
   • No signs of surrounding cellulitis
   • Normal host defenses

2. Antibiotics indicated if:

   • Signs of SIRS present (temperature >38°C or <36°C, tachypnea >24 breaths/min, tachycardia >90 beats/min, or WBC >12,000 or <400 cells/μL)
   • Markedly impaired host defenses
   • Extensive surrounding cellulitis
   • Failed initial treatment 1, 2

Antibiotic Selection for Infected Epidermoid Cysts

When antibiotics are indicated, selection should target the most likely pathogens (Staphylococcus aureus and streptococci):

For methicillin-susceptible S. aureus (MSSA):

• First-line oral options:
  • Dicloxacillin 500 mg four times daily
  • Cephalexin 500 mg four times daily
  • Clindamycin 300-450 mg four times daily (for penicillin-allergic patients) 1, 3

For suspected methicillin-resistant S. aureus (MRSA):

• Oral options:
  • Clindamycin 300-450 mg four times daily 1, 3
  • Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily
  • Doxycycline 100 mg twice daily 1

For severe infections requiring IV therapy:

• Vancomycin (for MRSA coverage)
• Nafcillin/oxacillin (for MSSA coverage) 1

Treatment Duration

• For most uncomplicated infections, 7-10 days of antibiotic therapy is sufficient 1
• For more severe infections, up to 14 days may be necessary

Common Pitfalls and Caveats

1. Overuse of antibiotics: Antibiotics are not routinely needed for simple incision and drainage of infected epidermoid cysts without systemic symptoms 1, 2

2. Incomplete drainage: Failure to adequately drain the cyst can lead to persistent infection and recurrence

3. Failure to recognize systemic infection: Always assess for signs of SIRS which would necessitate antibiotic therapy 1

4. Recurrence risk: Incision and drainage alone has a higher recurrence rate than complete excision, as the cyst wall may remain intact 4

5. Inappropriate antibiotic selection: When antibiotics are indicated, they should cover both S. aureus (including potential MRSA) and streptococci 5

6. Misdiagnosis: Ensure the lesion is truly an epidermoid cyst and not another entity that may require different management 6

For non-infected epidermoid cysts, complete surgical excision with removal of the entire cyst wall is recommended to prevent recurrence 2. However, for infected cysts, this approach should be delayed until the infection resolves to reduce the risk of surgical complications.