What antibiotic is recommended for a healthy young adult with a pilonidal cyst and signs of infection, such as increased redness, swelling, warmth, or purulent discharge, and no history of antibiotic allergies?

Antibiotic Selection for Infected Pilonidal Cyst

For a healthy young adult with an infected pilonidal cyst showing signs of purulent drainage, the primary treatment is incision and drainage, with antibiotics added only if systemic signs of infection (SIRS) are present—when antibiotics are indicated, clindamycin 300-450 mg orally three times daily plus trimethoprim-sulfamethoxazole (1-2 double-strength tablets twice daily) is the recommended first-line regimen. 1

When to Use Antibiotics

The decision to add antibiotics depends on the presence of systemic inflammatory response syndrome (SIRS) criteria: 2

• Temperature >38°C or <36°C
• Tachypnea >24 breaths per minute
• Tachycardia >90 beats per minute
• White blood cell count >12,000 or <4,000 cells/µL

If SIRS is absent, incision and drainage alone is sufficient without antibiotics. 2 This is a critical distinction—antibiotics are not routinely needed for simple pilonidal abscesses without systemic involvement.

First-Line Antibiotic Regimen

When antibiotics are indicated based on SIRS criteria: 1

• Clindamycin 300-450 mg orally three times daily PLUS
• Trimethoprim-sulfamethoxazole 1-2 double-strength tablets (160/800 mg) twice daily

This combination provides coverage for both Staphylococcus aureus (including MRSA) and anaerobic bacteria commonly found in the perineal region. 1

Alternative Regimens

For penicillin allergy: 1

• Clindamycin 300-450 mg orally three times daily PLUS ciprofloxacin 500-750 mg twice daily

For perineal/sacrococcygeal infections (alternative options): 1, 3

• Cefoxitin or ampicillin-sulbactam (particularly for hospitalized patients requiring IV therapy)

Avoid these antibiotics: 2, 1

• Amoxicillin or ampicillin monotherapy—these have poor efficacy and high resistance rates for skin infections

Duration of Therapy

• 5-7 days for uncomplicated cases following adequate drainage 1, 3
• Extend to 10-14 days if clinical improvement is inadequate or infection is more severe 1, 3
• The minimum duration should be 5 days, with extension if infection has not improved 2

Critical Management Principles

Incision and drainage is the cornerstone of treatment—failure to adequately drain the abscess is the most common cause of treatment failure, not antibiotic selection. 1, 3 The abscess must be thoroughly evacuated with probing to break up loculations. 2

Culture the abscess: Gram stain and culture of pus is recommended to guide antibiotic therapy, particularly for recurrent infections. 2, 3 This allows targeted therapy based on susceptibility patterns.

Search for underlying causes: A recurrent abscess at a previous site should prompt evaluation for persistent pilonidal disease, foreign material, or hidradenitis suppurativa. 2

Special Considerations for Recurrent Infections

For patients with recurrent pilonidal abscesses: 2

• Culture early in the course and treat with a 5-10 day course of antibiotics active against the isolated pathogen
• Consider a 5-day decolonization regimen: 2, 1
  • Intranasal mupirocin twice daily
  • Daily chlorhexidine body washes
  • Daily decontamination of personal items (towels, sheets, clothing)

Common Pitfalls to Avoid

Do not use beta-lactams as first-line agents—cephalexin and similar agents have shown inferior efficacy and more adverse effects compared to other antimicrobials for skin infections, though they may be acceptable when combined with proper drainage. 1, 3

Reserve fluoroquinolones for specific situations—they should not be first-line due to potential for collateral damage and resistance development. 1 Use only when other options cannot be used.

Do not confuse pilonidal infection with simple cellulitis—the terminology "cellulitis" is inappropriate for infections with pus collections; proper drainage is essential. 2

Hospitalization may be needed if there is concern for deeper or necrotizing infection, poor adherence to therapy, or severe immunocompromise. 2