What is the antibiotic of choice for a patient with a dog bite to the forearm, presenting with an abscess, elevated C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR), indicating a significant inflammatory response?

Antibiotic Treatment for Infected Dog Bite with Abscess

For this infected dog bite to the forearm with abscess formation and elevated inflammatory markers, amoxicillin-clavulanate 875/125 mg twice daily orally is the antibiotic of choice, or ampicillin-sulbactam 1.5-3.0 g IV every 6-8 hours if intravenous therapy is required. 1, 2

Why Amoxicillin-Clavulanate is First-Line

Amoxicillin-clavulanate provides comprehensive coverage of the polymicrobial flora in dog bite wounds as monotherapy, including the critical pathogens Pasteurella multocida (present in 50% of dog bites), Staphylococcus aureus, Streptococcus species, Capnocytophaga canimorsus, and anaerobes such as Bacteroides, Fusobacterium, and Porphyromonas species. 1, 2 Dog bite wounds yield an average of 5 different bacterial isolates per wound, with approximately 60% containing mixed aerobic and anaerobic bacteria. 1

The presence of an abscess with significantly elevated inflammatory markers (CRP 16, ESR 125) indicates established infection requiring treatment rather than prophylaxis. 1

Treatment Duration and Route

• For established infection with abscess: 7-10 days of antibiotic therapy 1, 2
• Oral therapy: Amoxicillin-clavulanate 875/125 mg twice daily 1
• IV therapy: Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours if systemic toxicity, inability to tolerate oral medications, or failure of oral therapy 1

Critical Adjunctive Management

Surgical drainage of the abscess is essential and should not be delayed. 1 The wound requires:

• Copious irrigation with sterile normal saline 1, 2
• Debridement of devitalized tissue 1, 2
• Elevation of the affected forearm to accelerate healing 1

Alternative Regimens (If Penicillin Allergy)

For patients with mild penicillin allergy:

• Cefoxitin 1 g IV every 6-8 hours 1
• Carbapenem (ertapenem 1 g daily, imipenem 1 g every 6-8 hours, or meropenem 1 g every 8 hours) 1

For patients with severe penicillin allergy:

• Moxifloxacin 400 mg daily (provides both aerobic and anaerobic coverage as monotherapy) 1
• OR Levofloxacin 750 mg daily plus metronidazole 500 mg every 8 hours 1, 2

Antibiotics to Avoid

Do not use the following as monotherapy as they miss critical pathogens:

• First-generation cephalosporins (cephalexin, cefazolin) - miss P. multocida and anaerobes 1, 2
• Clindamycin alone - misses P. multocida 1, 2
• Fluoroquinolones alone (without metronidazole) - miss anaerobes 1, 2
• TMP-SMX alone - poor anaerobic coverage 1, 2
• Macrolides - poor activity against P. multocida 1, 2

When to Escalate or Hospitalize

Consider hospitalization with IV antibiotics if: 2

• Infection progresses despite appropriate oral antibiotics
• Signs of systemic toxicity develop
• Patient is immunocompromised
• Deep space infection or osteomyelitis suspected (pain disproportionate to injury near bone/joint) 1

Hand wounds and wounds near joints warrant particular concern as they often require prolonged therapy: 3-4 weeks for septic arthritis and 4-6 weeks for osteomyelitis. 1

Additional Essential Considerations

• Tetanus prophylaxis: Administer if not vaccinated within 10 years 1
• Rabies evaluation: Consult local health officials to determine if post-exposure prophylaxis is needed 1
• MRSA coverage: Standard regimens miss MRSA; if suspected based on local epidemiology or clinical failure, add vancomycin or other anti-MRSA agent 1

Common Pitfall

Do not add fluoroquinolones to amoxicillin-clavulanate - this provides redundant coverage of key pathogens and is not indicated in routine cases. 2 Fluoroquinolones should only be considered for severe penicillin allergy or treatment failure. 2