What is the recommended treatment for cellulitis after a dog bite?

Treatment of Cellulitis After Dog Bite

For established cellulitis following a dog bite, use amoxicillin-clavulanate 875/125 mg twice daily orally as first-line therapy, covering the polymicrobial flora including Pasteurella multocida, streptococci, staphylococci, and anaerobes. 1, 2

First-Line Antibiotic Therapy

Amoxicillin-clavulanate is the preferred agent because dog bite infections are polymicrobial, with Pasteurella multocida isolated in 20-30% of cases, along with streptococci, staphylococci, and anaerobic organisms including Fusobacterium, Bacteroides, and Porphyromonas species. 1, 3, 4

Oral Regimens:

• Amoxicillin-clavulanate 875/125 mg twice daily (first choice) 1, 2
• Doxycycline 100 mg twice daily (excellent activity against P. multocida, though some streptococci are resistant) 1, 2
• Moxifloxacin 400 mg daily (provides monotherapy coverage including anaerobes) 1, 2
• Penicillin VK 500 mg four times daily PLUS dicloxacillin 500 mg four times daily 1, 2

Intravenous Regimens (for severe infections):

• Ampicillin-sulbactam 1.5-3.0 g every 6 hours 1, 2
• Piperacillin-tazobactam 3.37 g every 6-8 hours 1
• Carbapenems (see individual agent dosing) 1, 2
• Cefoxitin 1 g every 6-8 hours 1, 2

Treatment Duration

Treat established cellulitis for 5-10 days based on clinical response. 2 For preemptive therapy in high-risk wounds without established cellulitis, 3-5 days is sufficient. 1, 2

Critical Pitfalls to Avoid

Do not use cephalexin, dicloxacillin, or clindamycin as monotherapy for dog bite cellulitis—these agents miss P. multocida, which is present in 20-30% of dog bite wounds. 2, 3 First-generation cephalosporins and macrolides are also inadequate as single agents. 2

Note that all beta-lactam regimens miss MRSA, but MRSA is not a typical pathogen in dog bite infections unless there are specific risk factors (athletes, prisoners, healthcare exposure, IV drug users). 1, 5

Essential Wound Management

Beyond antibiotics, proper wound care is critical for preventing complications:

• Thorough wound cleansing with copious irrigation using sterile normal saline 2, 4
• Incision and drainage if abscesses are present 2, 4
• Elevation of the affected extremity to reduce edema 2
• Tetanus prophylaxis if not vaccinated within 10 years (Tdap preferred over Td if not previously given) 1
• Rabies postexposure prophylaxis consideration in consultation with local health officials 1, 2

High-Risk Situations Requiring Aggressive Treatment

Preemptive antimicrobial therapy is particularly important for patients with:

• Immunocompromised status 1, 2
• Asplenia 1, 2
• Advanced liver disease 1, 2
• Moderate to severe injuries, especially to the hand or face 1, 2
• Injuries that may have penetrated the periosteum or joint capsule 1
• Preexisting or resultant edema of the affected area 1

Hand wounds carry the greatest risk of infection and require particular vigilance for complications including septic arthritis, osteomyelitis, tendonitis, compartment syndrome, and nerve or tendon injury. 2, 3

Monitoring for Complications

Watch for systemic complications including bacteremia, endocarditis, and meningitis, particularly from Capnocytophaga species, which can cause severe invasive disease and rare complications like thrombotic microangiopathies. 6 These bacteria are slow-growing and may require extended culture time for identification. 6

If the patient fails to improve with appropriate first-line antibiotics, consider resistant organisms, secondary conditions mimicking cellulitis, or underlying complicating conditions such as immunosuppression, chronic liver disease, or chronic kidney disease. 5