How should uncomplicated cellulitis be treated in a 71‑year‑old woman?

Treatment of Cellulitis in a 71-Year-Old Woman

For uncomplicated cellulitis in a 71-year-old woman, prescribe cephalexin 500 mg orally every 6 hours (or dicloxacillin 250–500 mg every 6 hours) for exactly 5 days if clinical improvement occurs—do not add MRSA coverage unless specific risk factors are present. 1

First-Line Antibiotic Selection

• Beta-lactam monotherapy is the standard of care for typical uncomplicated cellulitis, achieving 96% clinical success because the primary pathogens are beta-hemolytic streptococci (especially Streptococcus pyogenes) and methicillin-sensitive Staphylococcus aureus. 1, 2

• Recommended oral beta-lactam options include:

  • Cephalexin 500 mg orally every 6 hours 1
  • Dicloxacillin 250–500 mg orally every 6 hours 1
  • Amoxicillin 500 mg orally three times daily 1
  • Penicillin V 250–500 mg orally four times daily 1

• MRSA is an uncommon cause of typical cellulitis even in high-prevalence settings, so routine MRSA coverage is unnecessary and represents overtreatment. 1, 3

Treatment Duration

• Treat for exactly 5 days if clinical improvement is evident (resolution of warmth and tenderness, improving erythema, no fever); extend only if symptoms have not improved within this timeframe. 1

• High-quality randomized controlled trial evidence demonstrates that 5-day courses are as effective as 10-day courses for uncomplicated cellulitis, making traditional 7–14-day regimens unnecessary. 1

When to Add MRSA Coverage (and When NOT To)

Add MRSA-active antibiotics ONLY when any of the following specific risk factors are present: 1

• Penetrating trauma or injection drug use 1
• Purulent drainage or exudate visible at the infection site 1
• Known MRSA colonization or prior MRSA infection 1
• Systemic inflammatory response syndrome (fever >38°C, heart rate >90 bpm, respiratory rate >24 breaths/min) 1
• Failure to respond to beta-lactam therapy after 48–72 hours 1

If MRSA coverage is indicated, use: 1

• Clindamycin 300–450 mg orally every 6 hours as single-agent therapy (covers both streptococci and MRSA), but only if local MRSA clindamycin resistance is <10% 1
• Alternative combination regimens:
  • Trimethoprim-sulfamethoxazole 1–2 double-strength tablets twice daily plus cephalexin or amoxicillin 1
  • Doxycycline 100 mg orally twice daily plus cephalexin or amoxicillin 1

Penicillin Allergy Management

• For non-immediate penicillin allergy (e.g., rash without anaphylaxis), cephalexin remains acceptable because cross-reactivity is only 2–4%. 1

• For true penicillin allergy, use clindamycin 300–450 mg orally every 6 hours (if local MRSA clindamycin resistance <10%). 1

Hospitalization Criteria

Admit the patient if any of the following are present: 1

• Systemic inflammatory response syndrome (fever, tachycardia, hypotension, altered mental status) 1
• Signs of deeper or necrotizing infection (severe pain out of proportion to examination, skin anesthesia, rapid progression, "wooden-hard" tissue, gas in tissue, bullous changes) 1
• Severe immunocompromise or neutropenia 1
• Failure of outpatient treatment after 24–48 hours 1

For hospitalized patients requiring IV therapy: 1

• Without MRSA risk factors: cefazolin 1–2 g IV every 8 hours or nafcillin 2 g IV every 6 hours 1
• With systemic toxicity or suspected necrotizing infection: vancomycin 15–20 mg/kg IV every 8–12 hours plus piperacillin-tazobactam 3.375–4.5 g IV every 6 hours 1

Essential Adjunctive Measures

• Elevate the affected extremity above heart level for at least 30 minutes three times daily to promote gravity drainage of edema and inflammatory substances—this is often neglected but critical. 1

• Examine interdigital toe spaces for tinea pedis, fissuring, scaling, or maceration and treat if present, as this eradicates colonization and reduces recurrent infection risk. 1

• Treat predisposing conditions including venous insufficiency, lymphedema, chronic edema, obesity, and eczema. 1

• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adults, though evidence is limited; avoid in diabetic patients. 1

Monitoring and Reassessment

• Reassess within 24–48 hours to verify clinical response, as treatment failure rates of approximately 21% have been reported with some oral regimens. 1

• If no improvement after 48–72 hours of appropriate therapy, consider:

  • Resistant organisms (MRSA) 1
  • Undrained abscess (obtain ultrasound if uncertain) 1
  • Deeper infection (necrotizing fasciitis, septic arthritis, osteomyelitis) 1
  • Cellulitis mimickers (venous stasis dermatitis, contact dermatitis, deep vein thrombosis) 4, 5

Common Pitfalls to Avoid

• Do not routinely add MRSA coverage for typical cellulitis without the specified risk factors—this drives antimicrobial resistance without improving outcomes. 1, 3

• Do not use doxycycline or trimethoprim-sulfamethoxazole as monotherapy for typical cellulitis, as they lack reliable activity against beta-hemolytic streptococci. 1

• Do not automatically extend therapy to 7–10 days based on residual erythema alone—some inflammation persists even after bacterial eradication. 1

• Do not delay surgical consultation if any signs of necrotizing infection are present—these infections progress rapidly and require emergent debridement. 1

Prevention of Recurrent Cellulitis

• Annual recurrence rates are 8–20% in patients with previous cellulitis, so addressing predisposing factors is essential. 1

• For patients with 3–4 episodes per year despite optimal management of risk factors, consider prophylactic antibiotics such as penicillin V 250 mg orally twice daily or erythromycin 250 mg twice daily. 1