Is Bactrim (trimethoprim/sulfamethoxazole) effective for treating an infected pilonidal cyst?

Bactrim for Infected Pilonidal Cyst

Trimethoprim-sulfamethoxazole (Bactrim) is an appropriate antibiotic choice for treating infected pilonidal cysts due to its effectiveness against the typical polymicrobial flora involved, including both aerobic and anaerobic bacteria.

Rationale for Using Bactrim

The 2014 Infectious Diseases Society of America (IDSA) guidelines for skin and soft tissue infections provide the framework for treating infected pilonidal cysts 1. While pilonidal cysts are not specifically addressed in detail, they fall under the category of skin and soft tissue infections with abscess formation.

Key considerations for antibiotic selection:

1. Microbiology: Pilonidal cyst infections typically involve a polymicrobial flora including:

   • Enteric gram-negative bacteria
   • Staphylococcus species (including potential MRSA)
   • Anaerobic bacteria

2. Antimicrobial coverage: Trimethoprim-sulfamethoxazole (Bactrim) provides:

   • Good coverage against MRSA
   • Effective against many enteric gram-negative bacteria
   • Reasonable tissue penetration

3. Antibiotic penetration: Unlike cystic liver infections where antibiotic penetration is a concern 1, pilonidal cysts that are infected and draining typically allow for adequate antibiotic penetration.

Treatment Algorithm

1. Initial assessment:

   • Evaluate for systemic signs of infection (fever, elevated WBC)
   • Assess the extent of surrounding cellulitis
   • Determine if abscess formation is present

2. Treatment approach:

   • Primary intervention: Incision and drainage if abscess is present
   • Antibiotic therapy: Trimethoprim-sulfamethoxazole (Bactrim)
     • Dosing: 1-2 double-strength tablets (160/800 mg) twice daily for 7-10 days
     • Alternative if contraindicated: Clindamycin or doxycycline

3. Follow-up:

   • Reassess in 48-72 hours
   • Consider definitive surgical management after acute infection resolves

Evidence Considerations

The IDSA guidelines recommend that recurrent abscesses at previous sites of infection (including pilonidal cysts) should be treated with incision and drainage, with adjunctive antimicrobial therapy when appropriate 1.

While specific high-quality studies on antibiotics for pilonidal cyst infections are limited, clinical practice is guided by the understanding of the polymicrobial nature of these infections and the need for coverage against both aerobic and anaerobic organisms.

Potential Pitfalls and Caveats

1. Surgical management is essential: Antibiotics alone are insufficient for definitive treatment of infected pilonidal cysts with abscess formation. Incision and drainage remain the cornerstone of therapy.

2. Resistance concerns: Local resistance patterns should be considered. If local MRSA prevalence exceeds 10-15%, coverage with an agent like trimethoprim-sulfamethoxazole becomes more important.

3. Duration of therapy: While the IDSA guidelines recommend 5 days for uncomplicated skin infections 1, infected pilonidal cysts often require 7-10 days of treatment due to their location and the polymicrobial nature of the infection.

4. Recurrence risk: Antibiotics treat the acute infection but do not prevent recurrence. Definitive surgical management should be considered after the acute infection resolves.

In conclusion, while surgical management remains the definitive treatment for pilonidal disease 2, trimethoprim-sulfamethoxazole is an appropriate antibiotic choice for the management of infected pilonidal cysts, particularly when there is concern for MRSA or when polymicrobial infection is suspected.