What are the recommended empiric intravenous (IV) antibiotics for a severe dog bite wound or infection?

Empiric IV Antibiotics for Severe Dog Bite Wounds/Infections

For severe dog bite wound infections, ampicillin-sulbactam (1.5-3g IV every 6 hours) is the recommended first-line empiric intravenous antibiotic therapy. 1

Microbiology of Dog Bite Wounds

Dog bite wounds typically contain a polymicrobial mixture of organisms:

• Aerobic bacteria:

  • Pasteurella species (found in 50% of dog bite wounds)
  • Staphylococcus species (including MRSA)
  • Streptococcus species (including S. pyogenes)
  • Capnocytophaga canimorsus (particularly dangerous in immunocompromised patients)

• Anaerobic bacteria:

  • Bacteroides species
  • Fusobacterium species
  • Porphyromonas species
  • Prevotella species
  • Peptostreptococci 2, 1

The average dog bite wound yields 5 different bacterial isolates, with approximately 60% containing mixed aerobic and anaerobic bacteria 2.

IV Antibiotic Options for Severe Infections

First-line options:

• Ampicillin-sulbactam: 1.5-3g IV every 6-8 hours (1-2g ampicillin + 0.5-1g sulbactam) 2, 1, 3
  • Provides excellent coverage against Pasteurella species and most anaerobes
  • FDA-approved dosing: 1.5-3g IV every 6 hours 3
  • Dose adjustment required for renal impairment 3

Alternative IV options:

• Piperacillin-tazobactam: 3.375g IV every 6-8 hours 2, 1
• Second-generation cephalosporins (e.g., cefoxitin) 2
• Carbapenems (e.g., ertapenem, imipenem, meropenem) 2

For penicillin-allergic patients:

• Fluoroquinolone (e.g., ciprofloxacin, levofloxacin) + metronidazole or clindamycin for anaerobic coverage 2, 1
• Doxycycline + clindamycin (for non-severe allergies) 1

Severity Assessment and Treatment Algorithm

Indications for IV antibiotics and hospitalization:

1. Severe infection: Presence of systemic inflammatory response syndrome (SIRS)
2. Moderate infection with complications:
   • Extensive cellulitis (>2cm erythema)
   • Deep tissue involvement
   • Involvement of joints, tendons, or bones
   • Immunocompromised status (e.g., asplenia, cirrhosis)
   • Poor response to oral therapy 2, 1

Treatment duration:

• Standard course: 7-14 days
• Extended treatment (3-4 weeks) for:
  • Osteomyelitis
  • Septic arthritis
  • Slow-resolving infections 2, 1

Adjunctive Management

1. Wound management:

   • Thorough cleansing with sterile normal saline
   • Debridement of devitalized tissue
   • Leave infected wounds open (do not close primarily)
   • Elevation of the injured body part 2, 1

2. Surgical consultation:

   • Required for deep infections, abscess formation, compartment syndrome, or necrotizing infections
   • Consider early surgical exploration for hand wounds (higher risk of complications) 2, 1

3. Tetanus prophylaxis:

   • Administer tetanus toxoid if vaccination status is not current or unknown 2

4. Rabies consideration:

   • Consult local health department for guidance based on local epidemiology 2

Special Considerations

Immunocompromised patients:

• Asplenic patients: Higher risk for overwhelming Capnocytophaga canimorsus sepsis
• Cirrhotic patients: Increased risk of severe infection and sepsis
• Elderly: May require dose adjustment for renal function 1, 4

Monitoring:

• Follow-up within 24-48 hours to assess response
• Monitor for signs of progressive infection (increasing pain, erythema, purulence)
• Consider inflammatory markers (CRP, ESR) if clinical assessment is equivocal 1

Common Pitfalls to Avoid

1. Inadequate coverage of Pasteurella species: First-generation cephalosporins, penicillinase-resistant penicillins (e.g., dicloxacillin), macrolides, and clindamycin alone have poor activity against Pasteurella multocida and should be avoided 2

2. Delayed treatment: Dog bite wounds can rapidly progress to severe infection, especially in immunocompromised hosts 4

3. Inappropriate wound closure: Infected wounds should not be closed primarily 2

4. Inadequate debridement: Thorough wound cleansing and debridement are essential components of management 2, 1

5. Failure to consider deep structure involvement: Always evaluate for potential tendon, joint, or bone involvement 1