What is the recommended antibiotic treatment and dosage for a 79-year-old female Long-Term Care (LTC) resident with normal renal function (Glomerular Filtration Rate (GFR) of 80) diagnosed with cellulitis?

Antibiotic Treatment for Cellulitis in a 79-Year-Old LTC Resident

For this 79-year-old female long-term care resident with uncomplicated cellulitis and normal renal function (GFR 80), treat with cephalexin 500 mg orally every 6 hours for 5 days, extending only if clinical improvement has not occurred within this timeframe. 1

First-Line Oral Antibiotic Regimen

Beta-lactam monotherapy is the standard of care for typical uncomplicated cellulitis, with a 96% success rate, confirming that MRSA coverage is unnecessary in this setting. 1

Recommended Oral Agents (Choose One):

• Cephalexin 500 mg orally every 6 hours 1
• Dicloxacillin 250-500 mg orally every 6 hours 1
• Amoxicillin 500 mg orally every 8 hours 1
• Amoxicillin-clavulanate 875/125 mg orally twice daily (if bite-related) 1

Treatment Duration:

• 5 days if clinical improvement occurs 1
• Extend beyond 5 days ONLY if symptoms have not improved within this timeframe 1
• Traditional 7-14 day courses are no longer necessary for uncomplicated cases 1

When to Add MRSA Coverage

Do NOT add MRSA coverage for typical nonpurulent cellulitis in LTC residents unless specific risk factors are present. 1 Long-term care facility residence alone is mentioned as a potential MRSA risk factor 2, but current IDSA guidelines emphasize that MRSA is an uncommon cause of typical cellulitis even in high-prevalence settings 1.

Add MRSA-Active Antibiotics ONLY if:

• Purulent drainage or exudate is present 1
• Penetrating trauma or injection drug use 1
• Known MRSA colonization or prior MRSA infection 1
• Systemic inflammatory response syndrome (SIRS) present 1

MRSA-Active Regimens (if indicated):

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

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

Renal Dosing Considerations

With a GFR of 80 mL/min, no dose adjustment is required for any of the recommended oral antibiotics. 3 This patient has normal renal function for her age, and standard dosing applies for all beta-lactams 3.

When to Consider IV Therapy or Hospitalization

Hospitalize and initiate IV antibiotics if any of the following are present:

• Systemic inflammatory response syndrome (fever >38°C, tachycardia >90 bpm, tachypnea >24 rpm) 1
• Hypotension or altered mental status 1
• Severe immunocompromise or neutropenia 1
• Signs of necrotizing fasciitis (severe pain out of proportion to exam, skin anesthesia, rapid progression, gas in tissue, bullous changes) 1

IV Regimen (if hospitalization required):

• Cefazolin 1-2 grams IV every 8 hours 3
• For severe cellulitis with systemic toxicity: Vancomycin 15-20 mg/kg IV every 8-12 hours PLUS piperacillin-tazobactam 3.375 grams IV every 6 hours 1

Adjunctive Measures

These non-antibiotic interventions hasten improvement and reduce recurrence risk:

• Elevate the affected extremity to promote drainage 1
• Examine and treat interdigital toe spaces for tinea pedis 1
• Address predisposing conditions: chronic edema, venous insufficiency, lymphedema, eczema 1

Common Pitfalls to Avoid

• Do NOT reflexively add MRSA coverage simply because the patient is in a long-term care facility 1
• Do NOT continue treatment beyond 5 days if clinical improvement has occurred 1
• Do NOT use combination therapy when monotherapy is appropriate 1
• Reassess in 24-48 hours to verify clinical response, as treatment failure rates of 21% have been reported with some regimens 1

Algorithm for Treatment Failure

If cellulitis is spreading despite appropriate beta-lactam therapy after 48 hours:

1. Reassess for necrotizing fasciitis warning signs (severe pain, skin anesthesia, rapid progression, systemic toxicity) 1
2. If necrotizing infection suspected: obtain emergent surgical consultation and initiate vancomycin or linezolid PLUS piperacillin-tazobactam 1
3. If no necrotizing signs: switch to MRSA-active therapy (clindamycin or vancomycin) 1
4. Never continue ineffective antibiotics beyond 48 hours 1