What antibiotics are recommended for a cat bite?

Antibiotic Treatment for Cat Bites

Amoxicillin-clavulanate 875/125 mg twice daily is the first-line antibiotic for cat bite wounds, whether for prophylaxis or treatment of established infection. 1, 2

Why Amoxicillin-Clavulanate is First-Line

• Cat bites have an exceptionally high infection rate of 20-80%, far exceeding the 3-18% rate seen with dog bites 3
• Pasteurella multocida is present in approximately 75-90% of cat bites and is the predominant pathogen requiring coverage 1, 2, 3
• Cat bite wounds contain an average of 5 different bacterial species, with 60% having mixed aerobic and anaerobic bacteria 1
• Amoxicillin-clavulanate provides excellent coverage against P. multocida, good activity against staphylococci and streptococci, and effective coverage against anaerobic organisms (Bacteroides, Fusobacterium, Porphyromonas) 1, 2
• The combination has demonstrated 100% susceptibility against P. multocida isolates in surveillance studies 3

Treatment Duration

• Uncomplicated infections: 5-7 days 2
• Septic arthritis or synovitis: 3-4 weeks total 1, 2
• Osteomyelitis: 4-6 weeks total 1

Alternative Regimens for Penicillin Allergy

For patients with penicillin allergies, use doxycycline 100 mg twice daily as the preferred alternative. 1, 2

• Doxycycline has excellent activity against P. multocida and is recommended by both IDSA and American College of Physicians 1, 2
• Second alternative: Fluoroquinolone (ciprofloxacin 500-750 mg twice daily or levofloxacin) PLUS metronidazole or clindamycin to cover anaerobes 1, 2
• Trimethoprim-sulfamethoxazole plus metronidazole is another option, though TMP-SMX alone has poor anaerobic coverage 2

Indications for IV Antibiotics

Switch to IV therapy for cat bites with systemic signs (fever, lymphangitis, significant cellulitis), deep tissue involvement, or in immunocompromised patients. 1

• First-line IV: Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1
• Alternative IV: Piperacillin-tazobactam 3.37 g every 6-8 hours 1
• Severe infections: Carbapenems (ertapenem 1 g daily, imipenem 1 g every 6-8 hours, or meropenem 1 g every 8 hours) 1
• Transition to oral amoxicillin-clavulanate once clinical improvement occurs, typically after 3-5 days of IV therapy for cellulitis 1

Critical Antibiotics to AVOID

Never use first-generation cephalosporins (cephalexin), penicillinase-resistant penicillins (dicloxacillin), macrolides (erythromycin, azithromycin), or clindamycin monotherapy for cat bites. 1, 2

• These agents have poor activity against P. multocida and clinical failures are well-documented 1, 2
• Azithromycin specifically has insufficient coverage against anaerobes and documented treatment failures with P. multocida 1

High-Risk Scenarios Requiring Aggressive Management

• Hand wounds carry the highest infection risk and may require more aggressive treatment, including consideration of prophylactic antibiotics even for minor-appearing wounds 1, 2, 4
• Deep puncture wounds, especially over joints or tendons, require close monitoring for septic arthritis and osteomyelitis 1, 2
• Infection typically develops rapidly within 12-24 hours, presenting with cellulitis, lymphangitis, and serosanguineous or purulent drainage 2, 5
• Pain disproportionate to visible inflammation suggests deeper infection requiring imaging and possible surgical intervention 2

Essential Adjunctive Measures

• Thorough wound irrigation and debridement is mandatory in addition to antibiotic therapy 1, 2
• Elevate the affected extremity to reduce swelling 1
• Do not primarily close infected wounds; allow healing by secondary intention 1
• Verify tetanus immunization status 4

Special Note on Cat-Scratch Disease

• For cat-scratch disease caused by Bartonella henselae (not bite wounds), use azithromycin 500 mg on day 1, then 250 mg daily for 4 additional days in patients >45 kg 2