What is the typical duration of antibiotic treatment for cellulitis resulting from a dog bite?

Antibiotic Duration for Cellulitis from Dog Bite

For cellulitis resulting from a dog bite, a 5-day course of antibiotics is recommended, but treatment should be extended if the infection has not improved within this time period. 1

Microbiology and Antibiotic Selection

• Dog bite wounds are polymicrobial, with approximately 5 bacterial types per wound, including Pasteurella species (50% of bites), staphylococci and streptococci (40% of bites), and Capnocytophaga canimorsus 2
• Amoxicillin-clavulanate is the antibiotic of choice for empiric treatment of dog bite infections due to its effectiveness against beta-lactamase producing organisms 2
• For patients allergic to penicillin, alternatives include:
  • Doxycycline 100 mg twice daily (good activity against Pasteurella multocida) 2
  • Fluoroquinolones plus metronidazol for anaerobic coverage 2
  • Moxifloxacin 400 mg daily as monotherapy 2

Duration of Treatment

• The Infectious Diseases Society of America (IDSA) recommends a 5-day course of antibiotics for uncomplicated cellulitis, with extension if improvement is not observed 1
• This recommendation is supported by research showing that 5 days of antibiotic therapy is as effective as 10 days for uncomplicated cellulitis 3
• A 2020 study found no association between longer antibiotic duration (>5 days) and improved outcomes at day 10 or day 30 4

Special Considerations for Dog Bite Cellulitis

• Cultures and microscopic examination of cutaneous aspirates, biopsies, or swabs should be considered for animal bites 1
• For cellulitis associated with animal bites, coverage against both MRSA and streptococci is recommended if there are systemic signs of infection 1
• Complications such as artritis septica, osteomyelitis, or abscess formation may require extended therapy (4-6 weeks for osteomyelitis) 2
• Hand wounds from dog bites are often more severe and may require longer treatment courses 2

Adjunctive Therapy

• Elevation of the affected area is recommended to promote drainage of edema and inflammatory substances 1
• Thorough wound cleaning with copious irrigation is essential and can significantly reduce infection risk 2
• Infected wounds should not be closed, though facial wounds may be an exception with proper care 2
• Tetanus prophylaxis should be administered if vaccination is not current within the last 10 years 2
• Systemic corticosteroids could be considered in non-diabetic adult patients with cellulitis to hasten resolution 1

Monitoring Response

• If no improvement is seen after 5 days of appropriate antibiotic therapy, treatment should be extended 1
• Pain disproportionate to the injury severity near a bone or joint may suggest periosteal penetration requiring longer therapy 2
• Watch for complications including septic arthritis, osteomyelitis, subcutaneous abscess formation, tendinitis, and bacteremia 2

Common Pitfalls

• Avoid using first-generation cephalosporins like cefalexin, penicillinase-resistant penicillins, macrolides, or clindamycin as monotherapy for dog bite infections 2
• Don't underestimate the severity of hand wounds from dog bites, which often require more aggressive management 2
• Failure to improve with appropriate first-line antibiotics should prompt consideration of resistant organisms or underlying conditions 5