What are the best antibiotics for an otherwise healthy adult with a cat bite?

Best Antibiotics for Cat Bite

Amoxicillin-clavulanate (Augmentin) 875/125 mg orally twice daily for 7-10 days is the definitive first-line antibiotic for cat bites in healthy adults, providing optimal coverage against Pasteurella multocida and the polymicrobial flora characteristic of these wounds. 1, 2, 3

Why Amoxicillin-Clavulanate is the Clear Winner

• Cat bites have an exceptionally high infection rate of 20-80%, far exceeding the 3-18% infection rate of dog bites, making antibiotic therapy critical 4
• Amoxicillin-clavulanate demonstrates 100% susceptibility against P. multocida, which is isolated in over 50% of all cat bite wounds and is the most commonly cultured pathogen 1, 4, 5
• The average cat bite yields 5 different bacterial isolates with approximately 60% having mixed aerobic and anaerobic bacteria, requiring broad-spectrum coverage that amoxicillin-clavulanate uniquely provides against P. multocida, staphylococci, streptococci, and anaerobes 3
• Approximately 90% of domestic cats carry P. multocida in their oral cavity, making prophylactic coverage essential regardless of the cat's apparent health status 4

Treatment Duration and Indications

• Prophylaxis for fresh wounds: 3-5 days for uncomplicated wounds 2
• Treatment of established infection: 7-10 days for uncomplicated cellulitis or soft tissue infection 1, 3
• Extended therapy: 7-14 days if early signs of infection are already present at presentation 2

High-Risk Wounds Requiring Immediate Antibiotic Prophylaxis

• Hand bites carry the highest infection risk and complication rate, with prophylactic antibiotics reducing infection significantly (NNT = 4) 2, 6
• Deep puncture wounds (the typical cat bite pattern) 2
• Wounds on hands, feet, face, or near joints 1, 2
• Immunocompromised patients 1, 2
• Any wound presenting >8-12 hours after injury 2

Alternative Regimens for Penicillin Allergy

Mild Penicillin Allergy

• Doxycycline 100 mg orally twice daily has excellent P. multocida activity, though some streptococci may be resistant 1, 2, 3

Severe Penicillin Allergy

• Fluoroquinolone options: Ciprofloxacin 500-750 mg twice daily OR levofloxacin 750 mg daily, though these miss MRSA and some anaerobes 1, 2, 3
• Combination therapy: Trimethoprim-sulfamethoxazole 160-800 mg twice daily PLUS metronidazole 250-500 mg four times daily for complete aerobic and anaerobic coverage 1, 3

Critical Antibiotics to AVOID

• First-generation cephalosporins (cephalexin, cefazolin) have inadequate coverage against P. multocida and anaerobes despite 98.37% susceptibility in some studies—the polymicrobial nature of cat bites makes them insufficient as monotherapy 1, 2, 3, 4
• Penicillinase-resistant penicillins (dicloxacillin, nafcillin) have poor P. multocida activity 2, 3
• Clindamycin monotherapy lacks adequate coverage against the polymicrobial flora 1, 3
• Penicillin alone is inadequate for polymicrobial coverage 1

When to Escalate to IV Antibiotics

• Ampicillin-sulbactam 1.5-3.0 g IV every 6-8 hours is first-line for hospitalized patients with systemic signs (fever, lymphangitis, significant cellulitis) 1, 2, 3
• Piperacillin-tazobactam 3.37 g IV every 6-8 hours is an alternative for severe infections 1, 3
• Indications for IV therapy include: systemic signs, deep tissue involvement, immunocompromised patients with moderate-to-severe injury, or failure of oral therapy 2, 3
• Transition strategy: 3-5 days of IV therapy followed by oral amoxicillin-clavulanate to complete the course 3

Essential Wound Management Beyond Antibiotics

• Thorough irrigation with sterile normal saline using a 20-mL or larger syringe 2, 7
• Evaluate tetanus immunization status 1, 2, 5
• Assess rabies risk (even domestic animals are often unvaccinated) 1, 7
• Avoid primary closure of puncture wounds 2
• Elevate the affected extremity 1, 2

Red Flags Requiring Immediate Return

• Increasing pain, redness, or swelling 1, 2
• Purulent drainage 1, 2
• Fever or systemic symptoms 1
• Decreased range of motion 2
• Hand wounds require particularly close monitoring for septic arthritis, osteomyelitis, or tendonitis 1

Common Pitfall: Cat Scratch Disease vs. Cat Bite Wound

• Cat scratch disease (CSD) is caused by Bartonella henselae and presents with regional lymphadenopathy 3 weeks after inoculation—this is a completely different entity 1
• For confirmed CSD with lymphadenopathy, azithromycin 500 mg on day 1, then 250 mg daily for 4 additional days is the treatment, NOT amoxicillin-clavulanate 1
• Do not confuse acute cat bite wound infection (which requires amoxicillin-clavulanate) with delayed-onset cat scratch disease (which requires azithromycin) 1