What is the most appropriate antibiotic for treating an infected dog bite?

Treatment for Infected Dog Bite Wounds

Amoxicillin-clavulanic acid is the first-line antibiotic treatment for infected dog bite wounds, not gentamicin, ampicillin, vancomycin, or clindamycin. 1

Microbiology of Dog Bite Infections

• Dog bite wounds are polymicrobial, typically containing an average of 5 different bacterial isolates per wound 1
• Approximately 50% of dog bite wounds contain Pasteurella species 1
• Staphylococci and streptococci are found in about 40% of dog bite wounds 1
• Capnocytophaga canimorsus, a gram-negative bacillus, can cause bacteremia and potentially fatal sepsis, especially in immunocompromised patients 1
• Both aerobic and anaerobic bacteria are commonly present, with 67% of wounds containing a mixture of both types 2

First-Line Antibiotic Treatment

• Amoxicillin-clavulanic acid is the empiric antibiotic of choice for infected dog bite wounds 1
• The combination effectively addresses beta-lactamase-producing organisms commonly present in animal bite wounds 1
• First-generation cephalosporins, penicillinase-resistant penicillins, macrolides, and clindamycin should be avoided as monotherapy due to poor activity against Pasteurella multocida 1, 3
• Ampicillin alone is inadequate due to beta-lactamase production by many organisms found in bite wounds 1, 4

Alternative Treatment Options for Penicillin-Allergic Patients

• Doxycycline 100 mg twice daily is an excellent alternative for penicillin-allergic patients, with good activity against Pasteurella multocida 1, 3
• Fluoroquinolones (ciprofloxacino, levofloxacino, moxifloxacino) plus metronidazole for anaerobic coverage 1
• Moxifloxacin 400 mg daily can be used as monotherapy, covering both aerobic and anaerobic organisms 1

Intravenous Treatment Options for Severe Infections

• Beta-lactam/beta-lactamase inhibitor combinations (such as ampicillin-sulbactam) 1, 3
• Piperacillin-tazobactam 1, 3
• Second-generation cephalosporins (such as cefoxitin) 1, 3
• Carbapenems (ertapenem, imipenem, meropenem) 1

Antibiotics to Avoid as Monotherapy

• Clindamycin is inadequate as monotherapy for dog bite infections due to poor coverage against key pathogens 1, 3
• First-generation cephalosporins like cefalexin 1, 3
• Penicillinase-resistant penicillins (dicloxacillin) 1, 3
• Macrolides (erythromycin) 1, 3
• Gentamicin alone is not recommended as it does not provide adequate coverage for the polymicrobial nature of these infections 1
• Vancomycin is not recommended as first-line therapy as it lacks activity against gram-negative organisms commonly found in dog bites 1

Comprehensive Wound Management

• Thorough wound cleaning with copious irrigation is essential and significantly reduces infection risk 1
• Infected wounds should not be closed 1
• Facial wounds may be an exception and can be closed primarily with meticulous wound care, copious irrigation, and prophylactic antibiotics 1
• Tetanus prophylaxis should be administered if vaccination is not current within the last 10 years 1

Complications and Special Considerations

• Potential complications include septic arthritis, osteomyelitis, subcutaneous abscess formation, tendinitis, and rarely bacteremia 1
• Hand wounds often carry higher risk than wounds in more fleshy body areas 1
• Pain disproportionate to the visible injury near a bone or joint may suggest periosteal penetration 1
• These complications may require prolonged therapy, such as 4-6 weeks for osteomyelitis 1