What are the treatment options for outpatient department (OPD) skin infections?

Treatment of Outpatient Skin Infections

For uncomplicated outpatient skin infections, treatment depends on whether the infection is purulent (abscess/furuncle) or non-purulent (cellulitis/erysipelas): purulent infections require incision and drainage as primary therapy, while non-purulent infections require antibiotics targeting Gram-positive organisms, with empiric MRSA coverage reserved for high-risk patients or treatment failures. 1

Classification and Initial Assessment

Outpatient skin infections must be categorized by:

• Purulent vs. non-purulent presentation - This determines whether drainage or antibiotics are primary therapy 1
• Severity markers - Temperature >38.5°C, heart rate >110 bpm, erythema >5 cm beyond wound margins, or immunocompromised status indicate need for systemic antibiotics 1
• Risk factors for MRSA - Recent hospitalization, long-term care facility residence, prior MRSA infection, or injection drug use 1

Purulent Infections (Abscesses, Furuncles, Carbuncles)

Primary Treatment

Incision and drainage is the definitive treatment for simple abscesses and does not require adjunctive antibiotics in immunocompetent patients without systemic signs. 1

• Gram stain and culture are recommended but treatment without these studies is reasonable in typical cases 1
• Antibiotics are unnecessary if erythema <5 cm, temperature <38.5°C, WBC <12,000 cells/µL, and pulse <100 bpm 1

When to Add Antibiotics

Add systemic antibiotics for purulent infections when: 1

• Severe or extensive disease (multiple sites, rapid progression)
• Signs of systemic illness (fever, tachycardia)
• Associated comorbidities (diabetes, immunosuppression)
• Extremes of age
• Lack of response to incision and drainage alone
• Difficult-to-drain location (face, hands, genitalia)

Antibiotic selection for purulent infections with systemic features:

• First-line oral agents: Trimethoprim-sulfamethoxazole, doxycycline, or clindamycin for 5-10 days 1
• These agents provide MRSA coverage, which is critical given community-acquired MRSA prevalence 1
• Cephalexin 500 mg three times daily is appropriate only when MRSA is ruled out 2

Non-Purulent Infections (Cellulitis, Erysipelas, Impetigo)

Impetigo

Topical mupirocin applied three times daily for 7 days is first-line therapy for limited impetigo. 3, 4

• Oral antibiotics are indicated for extensive disease or when topical therapy fails 1
• Oral regimen: Cephalexin or dicloxacillin 500 mg four times daily for 7 days 1, 2
• When MRSA suspected: Use trimethoprim-sulfamethoxazole, doxycycline, or clindamycin 1

Cellulitis and Erysipelas

Beta-lactam antibiotics targeting streptococci and methicillin-susceptible S. aureus are first-line for uncomplicated cellulitis. 1, 5

Oral regimens for mild-moderate cellulitis: 1, 2

• Cephalexin 500 mg three to four times daily
• Dicloxacillin 500 mg four times daily
• Amoxicillin-clavulanate 875 mg twice daily

Duration: 5-10 days, with clinical reassessment at 48-72 hours 1

Empiric MRSA Coverage Indications

Add MRSA-active therapy for cellulitis when: 1

• Purulent drainage present
• Prior MRSA infection
• High local MRSA prevalence
• Injection drug use
• Failure of beta-lactam therapy after 48-72 hours

MRSA-active oral agents: 1

• Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily
• Doxycycline 100 mg twice daily
• Clindamycin 300-450 mg three times daily

Special Circumstances

Bite Wounds (Animal and Human)

Amoxicillin-clavulanate 875 mg twice daily is the preferred oral agent for bite wound infections, providing coverage against Pasteurella, streptococci, staphylococci, and anaerobes. 1

• Alternative: Doxycycline 100 mg twice daily (excellent Pasteurella coverage but limited anaerobic activity) 1
• Duration: 7-10 days for established infection 1
• Prophylactic antibiotics for 3-5 days are indicated for high-risk bites: immunocompromised patients, hand/face wounds, deep punctures, or delayed presentation 1

Infected Damaged Skin (Burns, Pressure Ulcers)

Irrigation and debridement are primary interventions; antibiotics are reserved for systemic signs of infection or high-risk patients. 1

• When antibiotics needed: Use broad-spectrum coverage for aerobic and anaerobic organisms 1
• Appropriate regimens include amoxicillin-clavulanate or fluoroquinolone plus metronidazole 1

Injection Drug Users

Abscesses in injection drug users require special consideration beyond simple incision and drainage. 1

• Rule out endocarditis with persistent systemic signs 1
• Obtain radiography to exclude foreign bodies (broken needles) 1
• Perform duplex sonography for vascular complications 1
• Screen for HIV, HCV, HBV 1
• Empiric broad-spectrum antibiotics covering MRSA, Gram-negatives, and anaerobes are required 1

Critical Pitfalls to Avoid

Do not prescribe antibiotics for simple abscesses without drainage - This leads to treatment failure and promotes resistance 1

Do not delay reassessment - Patients not responding within 48-72 hours require re-evaluation for MRSA, deeper infection, or alternative diagnosis 1

Do not ignore MRSA risk factors - Empiric beta-lactam therapy will fail in MRSA infections; use MRSA-active agents when risk factors present 1

Do not use topical antibiotics for extensive infections - Systemic therapy is required for cellulitis, multiple lesions, or systemic signs 1, 4

Do not close bite wounds primarily (except facial wounds with copious irrigation and prophylactic antibiotics) - This increases infection risk 1