Dog Bite Antibiotic Management
First-Line Treatment
Amoxicillin-clavulanate 875/125 mg twice daily orally is the first-line antibiotic for dog bite infections, providing comprehensive coverage against the polymicrobial flora including Pasteurella multocida, Staphylococcus aureus, streptococci, and anaerobes 1. This recommendation is supported by both the American College of Physicians and the Infectious Diseases Society of America 2, 1.
For patients requiring intravenous therapy due to systemic symptoms, moderate-to-severe infection, or high-risk wounds, initiate ampicillin-sulbactam 1.5-3.0 g every 6-8 hours, piperacillin-tazobactam 3.37 g every 6-8 hours, or ertapenem 1 g daily for 3-5 days before transitioning to oral therapy 2, 1.
Management for Penicillin-Allergic Patients
Oral Options for Mild Penicillin Allergy
For penicillin-allergic patients, the preferred oral regimen is doxycycline 100 mg twice daily PLUS a fluoroquinolone (moxifloxacin 400 mg daily, levofloxacin 500-750 mg daily, or ciprofloxacin 500-750 mg twice daily) PLUS clindamycin 300 mg three times daily 2. This combination is necessary because:
- Doxycycline provides excellent activity against Pasteurella multocida but has poor coverage against some streptococci 2, 1, 3
- Fluoroquinolones cover Pasteurella and gram-negative organisms but miss MRSA and some anaerobes 2
- Clindamycin covers staphylococci, streptococci, and anaerobes but misses Pasteurella 2
Alternative oral regimen: Trimethoprim-sulfamethoxazole 160-800 mg twice daily PLUS clindamycin 300 mg three times daily 2. This combination provides good aerobic coverage with TMP-SMZ and anaerobic coverage with clindamycin, though TMP-SMZ has poor anaerobic activity alone 2.
Intravenous Options for Severe Penicillin Allergy
For patients with mild penicillin allergies (not immediate hypersensitivity reactions) requiring IV therapy, cefoxitin 1 g every 6-8 hours or a carbapenem (ertapenem 1 g daily, imipenem 1 g every 6-8 hours, or meropenem 1 g every 8 hours) can be used 2.
For patients with severe/immediate penicillin hypersensitivity reactions requiring IV antibiotics, use doxycycline 100 mg IV every 12 hours PLUS a fluoroquinolone (ciprofloxacin 400 mg IV every 12 hours, moxifloxacin 400 mg IV daily) PLUS clindamycin 600 mg IV every 8 hours 2, 4.
Immunocompromised Patients: Critical Considerations
High-Risk Features Requiring Aggressive Management
Immunocompromised patients require aggressive management with the following approach 1:
- Initiate IV antibiotics immediately for any signs of infection, even if mild 1
- Consider Capnocytophaga canimorsus coverage, which causes fulminant sepsis in asplenic, cirrhotic, or immunocompromised patients 1, 4
- Extend treatment duration: use 10-14 days for soft tissue infections (versus 7-10 days in immunocompetent patients) 1, 4
- Lower threshold for hospitalization and surgical consultation 1
Specific Antibiotic Selection for Immunocompromised Patients
For immunocompromised patients who are NOT penicillin-allergic, use amoxicillin-clavulanate 875/125 mg twice daily (or IV ampicillin-sulbactam if severe) 1, 4. This provides adequate coverage for Capnocytophaga species 1.
For immunocompromised patients WITH penicillin allergy, the combination regimen becomes more critical because Capnocytophaga is susceptible to fluoroquinolones and doxycycline but resistant to clindamycin alone 4. Use doxycycline 100 mg twice daily PLUS a fluoroquinolone (moxifloxacin 400 mg daily preferred for better anaerobic coverage) PLUS clindamycin 300 mg three times daily 2, 4.
Treatment Duration Algorithm
- Prophylaxis for high-risk wounds: 3-5 days 4
- Uncomplicated soft tissue infections: 7-10 days total 1
- Immunocompromised patients with soft tissue infection: 10-14 days 4
- Septic arthritis: 3-4 weeks total 1
- Osteomyelitis: 4-6 weeks total 1
Microbiology: Why Specific Coverage Matters
Dog bite wounds contain an average of 5 different bacterial species, with 60% yielding mixed aerobic and anaerobic organisms 1. The key pathogens requiring coverage include:
- Pasteurella multocida: Present in 20-30% of dog bites, causes rapid-onset cellulitis within 24 hours 5
- Staphylococcus aureus and streptococci: Common skin flora introduced by bite 1
- Anaerobes: Present in polymicrobial infections, require specific coverage 2, 1
- Capnocytophaga canimorsus: Causes fulminant sepsis in asplenic, cirrhotic, or immunocompromised patients 1, 4
Critical Pitfalls to Avoid
Never use monotherapy with first-generation cephalosporins (cephalexin, cefazolin), macrolides (azithromycin, erythromycin), or penicillinase-resistant penicillins (dicloxacillin) alone 2, 1. These agents have poor or no activity against Pasteurella multocida, which is present in 20-30% of dog bites and causes serious infections 2, 5.
Exercise heightened vigilance for hand wounds, which have higher rates of serious complications including septic arthritis and osteomyelitis due to proximity to joints and tendons 1, 6.
Do not overlook Capnocytophaga risk in patients with asplenia, advanced liver disease, or immunocompromised status—this organism causes fulminant sepsis with high mortality in these populations 1, 4.
Essential Adjunctive Management
Beyond antibiotics, proper wound management is critical 1, 4, 7:
- Copious irrigation with sterile normal saline using a 20-mL or larger syringe 7
- Debridement of devitalized or necrotic tissue 1, 4
- Wound exploration for tendon, bone, or joint involvement 1, 7
- Avoid primary closure of infected wounds or high-risk puncture wounds 4
- Elevation of injured extremity 4
- Tetanus prophylaxis if vaccination not current within 10 years 1, 7
- Rabies prophylaxis consultation with local health officials if indicated 1, 7
- Follow-up within 24 hours for all outpatients 4
High-Risk Wounds Requiring Prophylactic Antibiotics
Prophylactic antibiotics (versus treatment of established infection) should be given for 1, 4, 7: