What antibiotics are used to treat skin abscesses?

Antibiotic Treatment for Skin Abscesses

Primary Treatment Principle

Incision and drainage is the definitive treatment for skin abscesses, and antibiotics are not routinely required after adequate drainage unless specific high-risk features are present. 1, 2

Decision Algorithm for Antibiotic Use

Simple Abscesses (No Antibiotics Needed)

For simple, uncomplicated abscesses after adequate incision and drainage, antibiotics are not indicated if all of the following criteria are met: 1, 2

• Temperature <38.5°C
• Heart rate <100 beats/min
• White blood cell count <12,000 cells/µL
• Erythema and induration limited to <5 cm from wound edge
• No systemic signs of illness
• No immunosuppression or significant comorbidities (diabetes, HIV/AIDS, malignancy)
• Abscess not in difficult-to-drain location (face, hand, genitalia)
• No associated septic phlebitis
• No involvement of multiple infection sites

When to Add Antibiotics

Add systemic antibiotics when any of the following are present: 1, 2

• Systemic inflammatory response syndrome (SIRS) criteria: Temperature >38°C or <36°C, heart rate >90 beats/min, respiratory rate >24 breaths/min, or WBC >12,000 or <4,000 cells/µL
• Extensive surrounding cellulitis (erythema/induration extending ≥5 cm from wound edge)
• Rapid progression despite drainage
• Immunosuppression or significant comorbidities
• Extremes of age
• Abscess in difficult-to-drain anatomic location
• Incomplete source control

Antibiotic Selection

Oral Regimens for Outpatient Management

For purulent cellulitis or when antibiotics are indicated after drainage, the following MRSA-active agents are recommended: 1

First-line options:

• Trimethoprim-sulfamethoxazole (TMP-SMX): 1-2 double-strength tablets (160/800 mg) PO twice daily for adults; 4-6 mg/kg/dose (trimethoprim component) PO every 12 hours for children 1, 3, 4
• Clindamycin: 300-450 mg PO three times daily for adults; 10-13 mg/kg/dose PO every 6-8 hours (max 40 mg/kg/day) for children 1
• Doxycycline: 100 mg PO twice daily for adults; 2 mg/kg/dose PO every 12 hours for children >8 years and ≥45 kg 1
• Minocycline: 200 mg loading dose, then 100 mg PO twice daily for adults; 4 mg/kg loading dose, then 2 mg/kg/dose PO every 12 hours for children 1

Duration: 7-10 days based on clinical response 1, 3, 5

Comparative Efficacy Data

Recent high-quality evidence demonstrates that both clindamycin and TMP-SMX are superior to placebo when added to incision and drainage: 3

• Clindamycin cure rate: 83.1% vs. placebo 68.9% (P<0.001)
• TMP-SMX cure rate: 81.7% vs. placebo 68.9% (P<0.001)
• Clindamycin had lower recurrence rates at 1 month (6.8%) compared to TMP-SMX (13.5%, P=0.03) 3
• However, clindamycin had higher adverse event rates (21.9%) compared to TMP-SMX (11.1%) 3

Duration Considerations

For MRSA infections specifically, a 10-day course is superior to 3 days: 5

• 3-day TMP-SMX had 10.1% higher failure rate in MRSA infections (P=0.03)
• 3-day treatment had 10.3% higher recurrence rate within 1 month (P=0.046)
• Use full 7-10 day courses for documented or suspected MRSA 5

Intravenous Regimens for Severe Infections

For patients requiring hospitalization (systemic toxicity, rapidly progressive infection, failed outpatient therapy): 1

• Vancomycin: 15-20 mg/kg/dose IV every 8-12 hours for adults; 15 mg/kg/dose IV every 6 hours for children 1
• Linezolid: 600 mg PO/IV twice daily for adults; 10 mg/kg/dose PO/IV every 8 hours (max 600 mg/dose) for children 1, 6
• Daptomycin: Consider for complicated cases 2

Critical Pitfalls to Avoid

• Never rely on antibiotics alone without adequate drainage - studies show no benefit when drainage is incomplete 2
• Do not attempt needle aspiration - only 25% success rate overall and <10% with MRSA 2
• TMP-SMX should not be used as monotherapy for nonpurulent cellulitis due to inadequate coverage of β-hemolytic streptococci 1
• Avoid wound packing - causes more pain without improving healing outcomes 2, 7
• Do not use rifampin as monotherapy - rapid resistance development 1

Special Populations

Methicillin-Susceptible S. aureus (MSSA)

For documented MSSA infections, β-lactam antibiotics are preferred: 1

• First- or second-generation cephalosporins (cephalexin 500 mg PO four times daily)
• Dicloxacillin 500 mg PO four times daily
• Nafcillin or oxacillin 2 g IV every 6 hours for severe infections 1

Penicillin Allergy

For patients with penicillin allergy and MSSA infection, use clindamycin, TMP-SMX, or doxycycline as outlined above 1

Complex Abscesses (Perianal, Perirectal, IV Drug Use Sites)

Require broad-spectrum coverage including Gram-positive, Gram-negative, and anaerobic bacteria: 1

• Combination regimens with metronidazole plus ciprofloxacin or ceftriaxone
• Single-agent options: piperacillin-tazobactam, ampicillin-sulbactam, or carbapenems 1

Culture and Follow-up

• Obtain wound culture and Gram stain at time of drainage, particularly given rising MRSA prevalence 1, 2
• Re-evaluate at 7-10 days after treatment completion 1, 2
• Persistent fever or failure to improve indicates inadequate source control requiring repeat imaging or intervention 2