What is the recommended antibiotic treatment for a healthy adult patient with no known allergies, presenting with an animal bite, to prevent infection?

Antibiotic Treatment for Animal Bites

First-Line Recommendation

Amoxicillin-clavulanate 875/125 mg twice daily is the preferred antibiotic for animal bite wounds in healthy adults without allergies, providing comprehensive coverage against the polymicrobial flora including Pasteurella multocida, Staphylococcus aureus, Streptococcus species, and anaerobes. 1

When to Prescribe Antibiotics: Risk Stratification

Not all animal bites require antibiotics. The decision depends on timing and risk factors:

Timing-Based Decision

• Prescribe antibiotics ONLY if the patient presents within 24 hours of the bite for prophylaxis of high-risk wounds 1
• Do NOT prescribe antibiotics if the patient presents ≥24 hours after the bite without signs of infection, as prophylactic antibiotics are only beneficial when given early 1

High-Risk Wounds Requiring Antibiotics (if presenting within 24 hours)

• Wound location: Hand, foot, face, genital wounds, or wounds near joints 1
• Wound characteristics: Deep wounds, puncture wounds, wounds that may have penetrated periosteum or joint capsule 1
• Patient risk factors: Immunocompromised status, diabetes mellitus, advanced liver disease, asplenia, prosthetic joints or heart valves, pre-existing or resultant edema of the affected area 1

Signs of Established Infection (treat regardless of timing)

• Increasing pain, redness, swelling, or purulent discharge 2
• Systemic symptoms such as fever 1

Antibiotic Regimens

Oral Therapy (First-Line)

• Amoxicillin-clavulanate 875/125 mg twice daily - preferred agent 1, 3
• Take at the start of a meal to enhance absorption and minimize gastrointestinal intolerance 3

Alternative Oral Options (for penicillin allergy)

• Doxycycline 100 mg twice daily - excellent activity against Pasteurella multocida 1, 2
• Moxifloxacin as monotherapy 1
• Clindamycin plus a fluoroquinolone 1

Intravenous Therapy (for severe infections)

Use IV therapy for patients with systemic symptoms, moderate to severe infections, or high-risk wounds:

• Piperacillin-tazobactam 1
• Carbapenems (ertapenem, imipenem, meropenem) 1
• Second-generation cephalosporins (cefoxitin) 1
• Third-generation cephalosporins (ceftriaxone) plus metronidazole 1

Treatment Duration

• Prophylaxis for high-risk wounds: 3-5 days 1, 2
• Uncomplicated infections: 7-10 days 1
• Septic arthritis: 3-4 weeks 1
• Osteomyelitis: 4-6 weeks 1
• Hand wounds: Often require longer treatment due to serious nature 1

Essential Wound Management

Beyond antibiotics, proper wound care is critical:

• Copious irrigation with sterile normal saline using a 20-mL or larger syringe 2
• Cautious debridement of devitalized tissue only, preserving viable tissue 2
• Assessment for deep structure involvement: Check for potential nerve, tendon, bone, or joint involvement 2

Additional Required Interventions

• Tetanus prophylaxis: Administer if vaccination not current within 5-10 years; Tdap preferred over Td if not previously given 1, 2
• Rabies prophylaxis: Consult local health officials to determine need for post-exposure prophylaxis (immune globulin plus vaccination on days 0,3,7, and 14) 1, 2

Special Considerations by Animal Type

Dog Bites

• Account for 80% of animal bite emergency visits 1
• Infection rate: 5-25% 1
• Contain average of 5 different aerobic and anaerobic bacteria 1
• Common pathogens: Pasteurella species (50%), Staphylococcus aureus (40%), Streptococcus species (40%), anaerobes 1

Cat Bites

• Higher infection risk: 30-50% become infected 1, 4
• Pasteurella multocida carriage rate approximately 90% in domestic cats 5
• Puncture wounds are particularly high-risk 4

Facial Wounds (Exception to Standard Management)

• Primary closure is recommended after thorough cleaning and debridement, unlike other bite wounds 2
• Rich vascular supply reduces infection risk and improves cosmetic outcomes 2
• Preemptive antibiotic therapy for 3-5 days is strongly recommended for all facial bite wounds 2

Critical Pitfalls to Avoid

• Never use first-generation cephalosporins, macrolides, or penicillinase-resistant penicillins alone - they have poor activity against Pasteurella multocida, present in 50% of dog bites 1, 2
• Do not prescribe antibiotics "just in case" for late presentation (≥24 hours) without infection - this violates guidelines and promotes resistance 1
• Do not rely on topical antibiotics alone - they cannot adequately address polymicrobial flora 2
• Do not close infected wounds - primary closure only appropriate for clinically uninfected wounds after thorough cleaning 2
• Consider Capnocytophaga canimorsus in asplenic patients or those with liver disease - this pathogen requires special attention in these populations 1