What is the appropriate management for a patient with a dog bite to the extensor surface of the wrist that has failed outpatient oral antibiotics, now presenting with increased swelling, pain, purulent drainage, and a known amoxicillin allergy?

Management of Failed Outpatient Dog Bite with Purulent Discharge and Amoxicillin Allergy

This patient requires immediate hospitalization for intravenous antibiotics, surgical consultation for incision and drainage of the purulent collection, and wound exploration given the high-risk location (wrist extensor surface with potential tendon/joint involvement). 1

Immediate Surgical Management

Incision and drainage is the primary treatment for purulent collections and must be performed urgently. 1 The wrist location is particularly concerning because:

• Hand and wrist wounds have the highest infection risk and potential for serious complications including septic arthritis and osteomyelitis 2, 3
• The extensor surface may involve tendon sheaths or joint capsules, which dramatically worsens prognosis 2
• Purulent discharge indicates established infection requiring source control beyond antibiotics alone 1

Surgical exploration should assess for:

• Tendon, bone, or joint involvement 2
• Necrotic tissue requiring debridement 1
• Foreign bodies 2

Intravenous Antibiotic Selection (Given Amoxicillin Allergy)

For this patient with penicillin allergy, vancomycin PLUS either ceftriaxone with metronidazole OR a fluoroquinolone with metronidazole is recommended for empiric IV therapy. 1, 2

Specific IV Regimen Options:

Option 1 (Preferred): Vancomycin 15-20 mg/kg IV every 8-12 hours PLUS ceftriaxone 1-2g IV daily PLUS metronidazole 500mg IV every 8 hours 1, 2

Option 2: Vancomycin 15-20 mg/kg IV every 8-12 hours PLUS levofloxacin 750mg IV daily PLUS metronidazole 500mg IV every 8 hours 1, 2

Option 3 (if severe penicillin allergy contraindicates cephalosporins): Vancomycin PLUS moxifloxacin 400mg IV daily (provides both gram-negative and anaerobic coverage as monotherapy when combined with vancomycin) 2

Rationale for This Approach:

• Vancomycin covers MRSA, which is present in 40% of dog bite wounds and must be covered empirically in failed outpatient therapy 1, 2
• Dog bites contain an average of 5 different organisms including Pasteurella species (50%), Staphylococcus aureus (40%), Streptococcus species (40%), and anaerobes (Bacteroides, Fusobacterium, Porphyromonas, Prevotella) 2, 4, 5
• The combination provides comprehensive polymicrobial coverage while avoiding amoxicillin-clavulanate (the usual first-line agent) 2, 4, 3

Critical Pitfall to Avoid

Never use first-generation cephalosporins (cephalexin), macrolides, or penicillinase-resistant penicillins alone—they have poor activity against Pasteurella multocida, which is present in 50% of dog bite wounds. 2, 6, 5 This is likely why the outpatient therapy failed if an inappropriate agent was initially prescribed.

Treatment Duration Algorithm

Initial IV therapy: 3-5 days until the patient is afebrile, systemic symptoms resolve, and local signs of infection improve 2

Transition to oral therapy when clinically improved:

• Doxycycline 100mg PO twice daily (excellent Pasteurella coverage and safe in penicillin allergy) 1, 2
• Alternative: Moxifloxacin 400mg PO daily as monotherapy 2
• Alternative: Levofloxacin 750mg PO daily PLUS metronidazole 500mg PO three times daily 2

Total duration:

• 7-10 days for uncomplicated soft tissue infection 1, 2
• 3-4 weeks if septic arthritis is confirmed 2
• 4-6 weeks if osteomyelitis is present 2

Essential Adjunctive Measures

• Obtain wound cultures (aerobic and anaerobic) before starting antibiotics to guide definitive therapy 1, 2
• Tetanus prophylaxis if not current within 10 years 2, 3
• Rabies risk assessment with consultation to local health officials 2, 3
• Imaging: Plain radiographs to assess for foreign bodies, gas in soft tissues, or bone involvement; consider MRI if deep infection suspected 2

Why Hospitalization is Mandatory

This patient meets multiple criteria for hospitalization per IDSA guidelines 1:

• Failed outpatient oral antibiotic therapy 1
• Purulent drainage indicating complicated skin and soft tissue infection 1
• High-risk anatomic location (wrist/hand with potential joint or tendon involvement) 2, 3
• Systemic symptoms (increased pain and swelling suggesting progression) 1

The combination of surgical source control plus appropriate broad-spectrum IV antibiotics covering the polymicrobial flora (including MRSA and Pasteurella) while avoiding the patient's allergen is essential to prevent devastating complications such as septic arthritis, osteomyelitis, or loss of hand function. 1, 2