What antibiotics are recommended for a patient with an infected pilonidal cyst?

Antibiotics for Infected Pilonidal Cyst

Incision and drainage is the primary treatment for an infected pilonidal cyst, with antibiotics reserved as adjunctive therapy only when systemic signs of infection are present—specifically fever, tachycardia, tachypnea, abnormal white blood cell count, or when erythema extends more than 5 cm from the wound edge. 1, 2

When Antibiotics Are Indicated

Antibiotics should be added to surgical drainage under the following specific circumstances:

• Systemic inflammatory response syndrome (SIRS) is present, including fever, tachycardia, tachypnea, or abnormal white blood cell count 1, 3
• Extensive cellulitis with erythema and induration extending more than 5 cm from the wound edge 1
• Immunocompromised status, including diabetes, HIV, or patients on immunosuppressive therapy 1

The key clinical pitfall is attempting to treat an undrained abscess with antibiotics alone—this approach fails because antibiotics cannot adequately penetrate the abscess cavity, and surgical drainage remains the cornerstone of treatment. 2

Recommended Antibiotic Regimens

First-Line Therapy

Clindamycin 300-450 mg orally three times daily PLUS trimethoprim-sulfamethoxazole (1-2 double-strength tablets twice daily) is the preferred first-line regimen for moderate to severe infections. 2, 3 This combination provides optimal coverage for the polymicrobial flora typical of perineal infections, including anaerobes and skin flora.

Alternative Regimens

For patients with penicillin allergy, use clindamycin plus ciprofloxacin 2, 3

For perineal location specifically, cefoxitin or ampicillin-sulbactam are effective options, as these agents provide appropriate anaerobic coverage for this anatomic region 4, 2

Regimens to Avoid

Do not use amoxicillin or ampicillin monotherapy due to poor efficacy and high resistance rates 2

Beta-lactams have shown inferior efficacy and more adverse effects compared to other antimicrobials for skin infections 2, 3

Fluoroquinolones should be reserved only for cases where other antibiotics cannot be used, as they carry significant risk for collateral damage including C. difficile infection and resistance development 3

Duration of Therapy

• 5-7 days for uncomplicated cases following adequate drainage 2
• 10-14 days for more severe or complicated infections based on clinical response 2

Management of Recurrent Infections

For patients with recurrent pilonidal abscesses:

• Culture the abscess and treat with antibiotics active against the isolated pathogen 1
• Consider a 5-day decolonization regimen with intranasal mupirocin twice daily and chlorhexidine body washes 2, 3

Clinical Algorithm

1. Perform incision and drainage as the primary intervention 1, 3
2. Assess for systemic signs: Check temperature, heart rate, respiratory rate, white blood cell count, and measure extent of surrounding erythema 1
3. If systemic signs present OR erythema >5 cm: Start clindamycin 300-450 mg three times daily plus trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily for 7-10 days 2, 3
4. If penicillin allergy: Substitute ciprofloxacin for trimethoprim-sulfamethoxazole 2, 3
5. If no systemic signs and minimal cellulitis: Drainage alone is sufficient without antibiotics 1

Important Caveats

The most common reason for treatment failure is inadequate drainage, not antibiotic selection—ensure complete evacuation of the abscess cavity before attributing failure to antimicrobial choice. 2 While one study showed aspiration with cephalexin and metronidazole was effective in 83% of cases 5, this approach is not endorsed by major guidelines and should not replace formal incision and drainage when systemic signs are present.