What antibiotics are recommended for cat bites?

Antibiotic Treatment for Cat Bites

Amoxicillin-clavulanate (875/125 mg twice daily) is the first-line antibiotic for cat bites, providing essential coverage against Pasteurella multocida (present in 75% of cat bites), staphylococci, streptococci, and anaerobic organisms. 1, 2

Why Amoxicillin-Clavulanate is First-Line

• The IDSA recommends amoxicillin-clavulanate as first-line therapy because cat bite wounds contain an average of 5 different bacterial species, with approximately 60% having mixed aerobic and anaerobic bacteria 1, 2
• P. multocida is the predominant pathogen requiring coverage and is found in approximately 75% of cat bite wounds 1, 3
• Staphylococci and streptococci are present in ~40% of cat bites, while anaerobic bacteria (Bacteroides, Fusobacterium, Porphyromonas) are present in 65% 1, 3
• Infection can develop rapidly within 12-24 hours after a cat bite, making prompt antibiotic initiation critical 2, 4

Alternative Options for Penicillin-Allergic Patients

• Doxycycline (100 mg twice daily) is the preferred alternative due to its excellent activity against P. multocida, though some streptococci may be resistant 1, 2, 3
• For patients who cannot take doxycycline, fluoroquinolones (ciprofloxacin 500-750 mg twice daily or levofloxacin) plus metronidazole or clindamycin provide adequate coverage 1, 2
• Trimethoprim-sulfamethoxazole plus metronidazole is another alternative, as TMP-SMX alone has poor anaerobic coverage 2

Antibiotics to Absolutely Avoid

The following antibiotics have poor activity against P. multocida and should never be used for cat bites: 1, 2, 3

• First-generation cephalosporins (e.g., cephalexin)
• Penicillinase-resistant penicillins (e.g., dicloxacillin) as monotherapy
• Macrolides (e.g., azithromycin, erythromycin) - clinical failures documented with P. multocida
• Clindamycin monotherapy - completely misses P. multocida coverage

Treatment Duration

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

When to Use IV Antibiotics

Indications for hospitalization and IV therapy include: 1

• Systemic signs of infection (fever, lymphangitis, significant cellulitis)
• Deep tissue involvement (septic arthritis, osteomyelitis, tenosynovitis)
• Immunocompromised patients with moderate to severe injuries
• Rapidly progressing infection despite oral antibiotics

IV regimens: 1

• First-line: Ampicillin-sulbactam (1.5-3.0 g every 6-8 hours)
• Alternative: Piperacillin-tazobactam (3.37 g every 6-8 hours)
• Severe infections: Carbapenems (ertapenem 1 g daily, imipenem 1 g every 6-8 hours, or meropenem 1 g every 8 hours)
• Transition to oral amoxicillin-clavulanate once clinical improvement occurs 1

High-Risk Wounds Requiring Aggressive Management

Cat bites to the hand have the highest infection risk and complication rate: 1, 2, 5, 6

• Hand wounds should receive prophylactic antibiotics even with minor signs of infection 5
• Deep puncture wounds over joints or tendons require more aggressive treatment 2
• Prophylactic antibiotics reduce infection rates in hand bites (NNT = 4) 7
• Complications include septic arthritis, osteomyelitis, tendonitis, and long-term functional impairment 1, 5

Essential Wound Care Measures

• Thoroughly irrigate with copious sterile normal saline using a 20-mL or larger syringe 2, 8
• Explore wounds for tendon, bone involvement, or foreign bodies 8
• Do not primarily close infected wounds - allow healing by secondary intention 1, 2
• Elevate the affected extremity to reduce swelling and accelerate healing 1, 3
• Ensure tetanus prophylaxis is current 3, 8

Critical Pitfalls to Avoid

• Delayed treatment - infection develops within 12-24 hours, making early intervention essential 2, 4
• Inadequate antibiotic coverage - using agents with poor P. multocida activity leads to treatment failure 1, 2
• Relying on topical antibiotics alone - systemic coverage is mandatory for cat bites 3
• Missing signs of deep infection - watch for pain disproportionate to visible inflammation, which suggests deeper involvement 2
• Insufficient follow-up - outpatients require evaluation within 24 hours by phone or office visit 3

Special Consideration: Cat-Scratch Disease

• For cat-scratch disease caused by Bartonella henselae (not bite wounds), azithromycin is appropriate: 500 mg on day 1, then 250 mg for 4 additional days in patients >45 kg 2
• This is a distinct entity from cat bite wound infections and requires different management