What is the treatment for cellulitis (inflammation of the skin and subcutaneous tissues) caused by a dog bite?

Treatment of Cellulitis from Dog Bite

For cellulitis resulting from a dog bite, use amoxicillin-clavulanate 875/125 mg twice daily orally as first-line therapy, covering both aerobic and anaerobic bacteria including Pasteurella multocida, streptococci, staphylococci, and anaerobes. 1

Why Dog Bite Cellulitis Requires Different Coverage

Dog bite wounds are polymicrobial, containing an average of 5 different bacterial species per wound. 1, 2 The key difference from typical cellulitis is the high prevalence of Pasteurella multocida (isolated from 50% of dog bite wounds), along with streptococci, staphylococci, Bacteroides species, Fusobacterium, Capnocytophaga, and Porphyromonas species. 1, 2

Critical pitfall: Standard cellulitis antibiotics like cephalexin, dicloxacillin, first-generation cephalosporins, macrolides, and clindamycin all have poor activity against P. multocida and should be avoided in dog bite infections. 1

Specific Antibiotic Recommendations

Oral Therapy (Outpatient)

• Amoxicillin-clavulanate 875/125 mg twice daily is the preferred agent, providing coverage against Pasteurella, streptococci, staphylococci, and anaerobes 1
• Alternative oral options if amoxicillin-clavulanate cannot be used:
  • Doxycycline 100 mg twice daily (excellent activity against P. multocida, though some streptococci are resistant) 1
  • Moxifloxacin 400 mg daily (monotherapy with good anaerobic coverage) 1
  • Penicillin VK 500 mg four times daily PLUS dicloxacillin 500 mg four times daily 1

Intravenous Therapy (Severe Cases)

For patients requiring hospitalization due to severity, systemic toxicity, or inability to tolerate oral medications:

• Ampicillin-sulbactam 1.5-3.0 g every 6 hours IV 1
• Piperacillin-tazobactam 3.37 g every 6-8 hours IV 1
• Carbapenems (ertapenem, imipenem, or meropenem) 1
• Cefoxitin 1 g every 6-8 hours IV 1

Duration of Treatment

Treat for 3-5 days as preemptive therapy for patients with moderate to severe injuries, especially to the hand or face, or injuries that may have penetrated the periosteum or joint capsule. 1

For established cellulitis, continue treatment for 5-10 days based on clinical response. 1 Five days is sufficient if clinical improvement is evident. 1

High-Risk Situations Requiring Preemptive Antibiotics

The IDSA strongly recommends preemptive early antimicrobial therapy for patients who are: 1

• Immunocompromised
• Asplenic
• Have advanced liver disease
• Have preexisting or resultant edema of the affected area
• Have moderate to severe injuries, especially to the hand or face
• Have injuries that may have penetrated the periosteum or joint capsule

Essential Adjunctive Measures

Beyond antibiotics, proper wound management is critical:

• Thorough wound cleansing with copious irrigation using sterile normal saline 1, 2
• Incision and drainage if abscesses are present 1, 2
• Elevation of the affected extremity to promote drainage 3
• Tetanus prophylaxis if indicated 1
• Rabies postexposure prophylaxis may be indicated; consult local health officials 1

When MRSA Coverage Is Needed

MRSA is an unusual cause of typical cellulitis but should be considered in dog bite cellulitis if: 1, 4, 3

• Purulent drainage is present
• Patient is an injection drug user
• There is evidence of MRSA infection elsewhere
• Known MRSA nasal colonization
• Systemic inflammatory response syndrome (fever, tachycardia, hypotension)
• Failure to respond to initial beta-lactam therapy

If MRSA coverage is needed, add clindamycin 300-450 mg three times daily (which also covers streptococci and anaerobes) or trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily PLUS a beta-lactam for streptococcal coverage. 4, 3

Complications to Monitor

Hand wounds and injuries near bones or joints require particular vigilance for: 1

• Septic arthritis
• Osteomyelitis (requiring 4-6 weeks of therapy)
• Tendonitis
• Compartment syndrome
• Nerve or tendon injury

Pain disproportionate to injury severity near a bone or joint suggests periosteal penetration and warrants imaging and possible surgical consultation. 1

Common Pitfalls to Avoid

• Do not use cephalexin, dicloxacillin, or clindamycin alone for dog bite cellulitis—they miss P. multocida 1
• Do not use first-generation cephalosporins or macrolides as monotherapy 1
• Do not delay treatment in high-risk patients (hand/face injuries, immunocompromised, asplenic) 1
• Do not forget rabies prophylaxis consideration in appropriate cases 1