Which antibiotic should be added to amoxicillin‑clavulanate in an adult patient without β‑lactam allergy and with normal renal function who has cellulitis after a dog bite?

No Additional Antibiotic Should Be Added to Augmentin for Dog Bite Cellulitis

Amoxicillin-clavulanate (Augmentin) alone provides complete coverage for dog bite infections and should not be supplemented with additional antibiotics. 1, 2

Why Augmentin Monotherapy Is Sufficient

Augmentin already covers all relevant pathogens in dog bite wounds, including:

• Pasteurella multocida (present in 50% of dog bites) 1
• Streptococci and staphylococci (found in ~40% of bites) 1
• Anaerobic bacteria (Bacteroides, Fusobacterium, Porphyromonas, Prevotella) 1
• Capnocytophaga canimorsus 1

The average dog bite wound contains 5 different bacterial species (both aerobic and anaerobic), and Augmentin provides single-agent coverage for this polymicrobial flora. 2

Recommended Dosing and Duration

For established infection with cellulitis:

• Augmentin 875/125 mg orally twice daily for 7-10 days 2
• For prophylaxis in high-risk wounds: 3-5 days 2

Why Adding Another Antibiotic Is Inappropriate

Adding a second agent creates redundant coverage without improving outcomes:

• Fluoroquinolones (like levofloxacin) would duplicate coverage of Pasteurella and gram-negatives already covered by Augmentin 2
• MRSA coverage is not indicated for typical animal bites, as the guideline table explicitly notes that Augmentin "misses MRSA" but this is acceptable because MRSA is not a typical dog bite pathogen 1
• Clindamycin alone would miss Pasteurella multocida, a key pathogen 1

When to Consider Alternative Therapy (Not Additional Therapy)

Switch (don't add) to alternative regimens only if:

• Severe penicillin allergy: Use a fluoroquinolone (ciprofloxacin 500-750 mg twice daily or levofloxacin 750 mg daily) plus metronidazole 500 mg three times daily 1
• Treatment failure after 48-72 hours: Consider hospitalization with IV ampicillin-sulbactam 1.5-3.0 g every 6 hours or piperacillin-tazobactam 3.37 g every 6-8 hours 1

Critical Pitfalls to Avoid

Do not add MRSA coverage (vancomycin, doxycycline, or TMP-SMX) to Augmentin for dog bite cellulitis—MRSA is not part of the typical dog bite flora and the guidelines explicitly list that Augmentin "misses MRSA" as an acceptable limitation 1

Do not use first-generation cephalosporins, clindamycin alone, or macrolides as these have poor activity against Pasteurella multocida and should be avoided entirely 1, 2

Essential Adjunctive Measures

• Copious irrigation with sterile normal saline 2
• Elevation of the affected extremity if swollen 1
• Tetanus prophylaxis if not vaccinated within 10 years 1
• Rabies evaluation in consultation with local health officials 1, 2
• Avoid primary wound closure except for facial wounds 2

Evidence Quality

This recommendation is based on strong evidence (A-II level) from the 2014 IDSA Skin and Soft Tissue Infection Guidelines, which explicitly state that "an antimicrobial agent or agents active against both aerobic and anaerobic bacteria such as amoxicillin-clavulanate should be used" as monotherapy. 1