What are the first and second line treatments for an abscess?

Abscess Treatment: First and Second Line Approaches

For simple cutaneous abscesses, incision and drainage (I&D) is the primary and definitive treatment, with antibiotics reserved for specific high-risk situations; for intra-abdominal abscesses, treatment is stratified by size—small abscesses (<4-5 cm) are treated with antibiotics alone, while large abscesses require percutaneous drainage plus antibiotics as first-line therapy. 1

Simple Cutaneous Abscesses

First-Line Treatment

• Incision and drainage alone is the primary treatment for simple cutaneous abscesses without need for antibiotics 1, 2
• Simple abscesses are defined as those with induration and erythema limited only to the defined abscess area, not extending beyond borders, and without multiloculated extension into deeper tissues 1

When to Add Antibiotics (First-Line Adjunct)

Add antibiotic therapy to I&D when any of the following are present 1:

• Severe or extensive disease involving multiple sites of infection
• Rapid progression with associated cellulitis
• Signs of systemic illness (fever, tachycardia, hypotension)
• Immunosuppression or significant comorbidities
• Extremes of age (very young or elderly)
• Difficult drainage locations (face, hand, genitalia)
• Associated septic phlebitis
• Lack of response to I&D alone

Antibiotic Selection for Cutaneous Abscesses

For outpatient empiric coverage of CA-MRSA 1:

• Clindamycin 150-450 mg PO every 6-8 hours 1, 3
• Trimethoprim-sulfamethoxazole (TMP-SMX) 1, 4
• Doxycycline or minocycline 1
• Linezolid 1

Duration: 5-10 days based on clinical response 1

Evidence note: A 2017 multicenter trial of 786 patients with abscesses ≤5 cm demonstrated that clindamycin or TMP-SMX plus I&D achieved 83.1% and 81.7% cure rates respectively, compared to 68.9% with I&D alone 5. Clindamycin showed lower recurrence at 1 month (6.8% vs 13.5% for TMP-SMX) but higher adverse events (21.9% vs 11.1%) 5.

Complex Abscesses (Perianal, Perirectal, IV Drug Sites)

First-Line Treatment

• Surgical incision and drainage is mandatory and should be performed promptly 1
• Add empiric broad-spectrum antibiotics covering gram-positive, gram-negative, and anaerobic bacteria 1

Critical caveat: Inadequate antibiotic coverage after drainage results in a 6-fold increase in readmission rates (28.6% vs 4%) 6. The inadequate coverage group had significantly higher abscess recurrence, with more than half readmitted ≥30 days post-procedure 6.

Intra-Abdominal Abscesses (Including Diverticular)

First-Line Treatment: Size-Based Algorithm

Small abscesses (<4-5 cm) 1:

• Antibiotics alone for 7 days in immunocompetent patients 1
• Pooled failure rate of 20% with mortality rate of 0.6% 1

Large abscesses (≥4-5 cm) 1:

• Percutaneous drainage PLUS antibiotics is first-line treatment
• Antibiotic duration: 4 days if source control adequate in immunocompetent, non-critically ill patients 1
• Up to 7 days in immunocompromised or critically ill patients based on clinical response and inflammatory markers 1

Second-Line Treatment (When Drainage Not Feasible)

For large abscesses when percutaneous drainage unavailable or not feasible 1:

• Immunocompetent, non-critically ill patients: Antibiotics alone with careful clinical monitoring 1
• Critically ill or immunocompromised patients: Surgical intervention should be considered 1

Important evidence: A retrospective study of 146 patients with diverticular abscesses ≥3 cm showed that antibiotics alone had 25% urgent surgery rate vs 18% after percutaneous drainage (p=0.21), but the antibiotic-alone group had significantly smaller mean abscess diameter (5.9 vs 7.1 cm) 1

Antibiotic Regimens for Intra-Abdominal Abscesses

Immunocompetent, non-critically ill patients with adequate source control 1:

• Piperacillin/tazobactam 6 g/0.75 g loading dose, then 4 g/0.5 g every 6 hours OR 16 g/2 g continuous infusion
• Eravacycline 1 mg/kg every 12 hours

Inadequate/delayed source control OR high risk for ESBL-producing organisms 1:

• Ertapenem 1 g every 24 hours
• Eravacycline 1 mg/kg every 12 hours

Septic shock 1:

• Meropenem 1 g every 6 hours by extended or continuous infusion
• Doripenem 500 mg every 8 hours by extended or continuous infusion
• Imipenem/cilastatin 500 mg every 6 hours by extended infusion
• Eravacycline 1 mg/kg every 12 hours

Beta-lactam allergy 1:

• Eravacycline 1 mg/kg every 12 hours
• Tigecycline 100 mg loading dose, then 50 mg every 12 hours

Monitoring and Treatment Failure

Patients with ongoing signs of infection or systemic illness beyond 7 days of antibiotic treatment warrant diagnostic investigation 1. This includes repeat imaging to assess for undrained collections, treatment failure, or complications requiring surgical intervention.

Key Clinical Pitfalls

• Do not use rifampin as single agent or adjunctive therapy for skin/soft tissue infections 1
• Wound packing may reduce recurrence in wounds >5 cm but is not universally required 2
• Antibiotic penetration into abscesses is limited and highly dependent on abscess maturation; substantial concentrations can be achieved with appropriate agent selection and optimal dosing, but efficacy may be hampered by low pH, protein binding, and bacterial enzyme degradation 7
• For Crohn's disease-related abscesses: Percutaneous drainage plus antibiotics is first-line when feasible, with success rates of 74-100%; surgery should be delayed when possible to reduce postoperative complications and stoma rates 8