What is the treatment for a dog bite with cellulitis?

Treatment of Dog Bite with Cellulitis

For a dog bite with cellulitis, use amoxicillin-clavulanate as first-line therapy, as it provides coverage against the typical pathogens including Pasteurella multocida, streptococci, staphylococci, and anaerobes that cause these infections. 1

Antibiotic Selection

First-Line Oral Therapy

• Amoxicillin-clavulanate 875/125 mg twice daily is the recommended agent for outpatient management 1, 2
• This combination specifically covers the polymicrobial flora from dog bites, including:
  • Pasteurella multocida (isolated from 50% of dog bite wounds) 1
  • Staphylococcus aureus and streptococci (found in ~40% of bites) 1
  • Anaerobes including Bacteroides, Fusobacterium, and Peptostreptococcus species 1
  • Capnocytophaga canimorsus 1

Alternative Oral Regimens (if amoxicillin-clavulanate cannot be used)

• Doxycycline 100 mg twice daily (excellent activity against P. multocida, though some streptococci may be resistant) 1
• Penicillin VK 500 mg four times daily PLUS dicloxacillin 500 mg four times daily 1
• Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) or trimethoprim-sulfamethoxazole PLUS metronidazole or clindamycin for anaerobic coverage 1

Agents to AVOID

Do NOT use first-generation cephalosporins (cephalexin), penicillinase-resistant penicillins alone (dicloxacillin monotherapy), macrolides (erythromycin), or clindamycin monotherapy as they have poor activity against P. multocida 1

Intravenous Therapy (for severe infections)

Use IV therapy for patients with systemic signs of infection (fever, hypotension, altered mental status), inability to tolerate oral medications, or failed outpatient therapy 1:

• Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1
• Piperacillin-tazobactam 3.37 g every 6-8 hours 1
• Cefoxitin 1 g every 6-8 hours 1
• Carbapenems (ertapenem, imipenem, meropenem) 1

Treatment Duration

• 5 days of antibiotic therapy is sufficient if clinical improvement has occurred 1
• Extend treatment if infection has not improved within this timeframe 1
• Complicated infections (septic arthritis, osteomyelitis, deep tissue involvement) require 4-6 weeks of therapy 1

Essential Adjunctive Measures

Wound Management

• Irrigation and debridement of necrotic tissue are critical to prevent invasive infection 1
• Deep irrigation under pressure is NOT recommended as it may spread bacteria into deeper tissue layers 1
• Surgical drainage is required for purulent collections or abscesses 1

Supportive Care

• Elevation of the affected extremity accelerates healing by promoting gravity drainage of edema and inflammatory substances 1
• This is an often-neglected but important aspect of treatment 1

Evaluation for Complications

• Pain disproportionate to injury near a bone or joint suggests periosteal penetration and requires evaluation for osteomyelitis or septic arthritis 1
• Hand wounds are particularly serious and prone to complications 1, 3
• Consider imaging (radiography for foreign bodies, ultrasound for vascular complications) 1

High-Risk Patients Requiring Preemptive Therapy

Initiate antibiotics for 3-5 days in patients with: 1

• Immunocompromised status
• Asplenia (risk for Capnocytophaga canimorsus sepsis) 1
• Advanced liver disease
• Preexisting or resultant edema of the affected area
• Moderate to severe injuries, especially to the hand or face
• Injuries that may have penetrated periosteum or joint capsule

Additional Considerations

Rabies and Tetanus

• Consult local health officials regarding rabies post-exposure prophylaxis 1
• Ensure tetanus immunization is current 4

MRSA Coverage

MRSA is uncommon in typical dog bite cellulitis 1. However, add MRSA coverage (vancomycin, daptomycin, linezolid, or oral doxycycline/clindamycin/TMP-SMX) if: 1

• Penetrating trauma with purulent drainage
• Evidence of MRSA infection elsewhere
• Known MRSA colonization
• Injection drug use history
• Systemic inflammatory response syndrome (SIRS)

Clinical Pitfalls

• Cellulitis may worsen initially after starting antibiotics due to sudden pathogen destruction releasing inflammatory enzymes—this does not indicate treatment failure 1
• The average dog bite wound yields 5 types of bacterial isolates (range 0-16), with ~60% showing mixed aerobic and anaerobic bacteria 1
• Wounds presenting >8-12 hours after injury typically have established infection requiring more aggressive management 1