What is the best treatment for a patient with cellulitis of the toe following a pedicure, considering potential penicillin allergy and possible methicillin-resistant Staphylococcus aureus (MRSA) infection?

Treatment of Toe Cellulitis Following Pedicure

For toe cellulitis after a pedicure, start with oral dicloxacillin 250-500 mg every 6 hours or cephalexin 500 mg four times daily for 5 days, extending only if symptoms have not improved within this timeframe. 1, 2, 3

Initial Antibiotic Selection Algorithm

Step 1: Assess for purulent drainage or MRSA risk factors

• Examine the toe carefully for any purulent drainage, exudate, or fluctuance 1, 2
• Check specifically for penetrating trauma from pedicure instruments 1, 3
• Look for systemic signs: fever >38.5°C, heart rate >110 bpm, or altered mental status 1, 3

Step 2: Choose antibiotic based on clinical presentation

For typical nonpurulent cellulitis (no drainage, no systemic toxicity):

• First-line: Dicloxacillin 250-500 mg orally every 6 hours 2, 4
• Alternative: Cephalexin 500 mg orally four times daily 1, 2, 3
• Duration: Exactly 5 days if clinical improvement occurs 1, 2, 3

Beta-lactam monotherapy succeeds in 96% of typical cellulitis cases because MRSA is uncommon in nonpurulent cellulitis, even in high-prevalence settings 2, 3. The pathogen is almost always beta-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus 3, 5.

Managing Penicillin Allergy

If the patient reports penicillin allergy:

• For mild/non-immediate reactions: Cephalexin remains safe (cross-reactivity is only 2-4%) 2
• For documented immediate-type reactions: Clindamycin 300-450 mg orally every 6 hours 1, 2, 3

Clindamycin provides single-agent coverage for both streptococci and MRSA, eliminating the need for combination therapy, but use only if local MRSA clindamycin resistance rates are <10% 1, 2, 3.

When to Add MRSA Coverage

Add MRSA-active antibiotics ONLY if specific risk factors are present:

• Purulent drainage or exudate visible on examination 1, 3
• Penetrating trauma from pedicure instruments (nail file, cuticle cutter) 1, 3
• Evidence of MRSA infection elsewhere or known MRSA colonization 1, 3
• Systemic inflammatory response syndrome (SIRS) 1, 3

MRSA-active regimens for outpatients:

• Clindamycin 300-450 mg orally every 6 hours (covers both streptococci and MRSA) 1, 2, 3
• Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily PLUS cephalexin 500 mg four times daily 1, 2
• Doxycycline 100 mg twice daily PLUS cephalexin 500 mg four times daily 1, 2

Critical caveat: Never use trimethoprim-sulfamethoxazole or doxycycline as monotherapy for cellulitis—their activity against beta-hemolytic streptococci is unreliable 1, 2, 3.

Special Consideration: Pseudomonas Risk

Pedicure-associated infections carry unique risk for Pseudomonas aeruginosa, particularly if there was water exposure or nail puncture 6. However, empiric Pseudomonas coverage is unnecessary unless the patient has specific risk factors: immunocompromise, diabetes with vascular disease, or signs of deeper infection 1.

If Pseudomonas is subsequently cultured, switch to ciprofloxacin 750 mg orally twice daily for 7-14 days after surgical debridement 6.

Essential Adjunctive Measures

These interventions are as important as antibiotics:

• Elevate the affected foot above heart level for at least 30 minutes three times daily to promote drainage 1, 2
• Examine interdigital toe spaces for tinea pedis, fissuring, scaling, or maceration—treat these to eradicate colonization and reduce recurrence 1, 2
• Mark the border of erythema with a pen to track progression or improvement 2

When to Hospitalize

Admit for IV antibiotics if ANY of the following are present:

• Systemic inflammatory response syndrome: fever, tachycardia, tachypnea 1, 3
• Hypotension or altered mental status 1, 3
• Severe pain out of proportion to examination (suggests necrotizing infection) 2
• Rapid progression despite 48 hours of appropriate oral antibiotics 2
• Severe immunocompromise or neutropenia 1, 3

For hospitalized patients with severe cellulitis:

• Vancomycin 15-20 mg/kg IV every 8-12 hours PLUS piperacillin-tazobactam 3.375-4.5 g IV every 6 hours 1, 2, 3
• Duration: 7-10 days for severe infections, reassessing at 5 days 2

Treatment Duration and Follow-Up

Stop antibiotics after exactly 5 days if:

• Warmth and tenderness have resolved 3
• Erythema is improving (some residual redness is normal) 3
• Patient is afebrile 3

Extend treatment beyond 5 days ONLY if:

• No improvement in warmth, tenderness, or erythema 1, 2, 3
• New systemic symptoms develop 3

Mandatory reassessment at 24-48 hours to verify clinical response, as treatment failure rates reach 21% with some regimens 2. Do not reflexively extend to 7-10 days based on tradition—this increases antibiotic resistance without improving outcomes 3.

Common Pitfalls to Avoid

• Do not add MRSA coverage reflexively for typical nonpurulent toe cellulitis—this represents overtreatment 2, 3
• Do not use doxycycline or trimethoprim-sulfamethoxazole alone—they lack reliable streptococcal coverage 1, 2, 3
• Do not continue ineffective antibiotics beyond 48 hours—progression indicates resistant organisms or deeper infection 2
• Do not miss an abscess—use ultrasound if there is any fluctuance, as drainage is primary treatment 2
• Do not delay surgical consultation if severe pain, skin anesthesia, rapid progression, or systemic toxicity are present—these suggest necrotizing fasciitis 1, 2