What is the recommended antibiotic prophylaxis for a cat bite?

Cat Bite Antibiotic Prophylaxis

Amoxicillin-clavulanate 875/125 mg twice daily is the first-line antibiotic prophylaxis for cat bites, covering the polymicrobial flora including Pasteurella multocida, which is present in approximately 75% of cat bite wounds. 1

Why Cat Bites Require Aggressive Treatment

• Cat bites have an exceptionally high infection rate of 30-50%, significantly higher than dog bites (5-25%), making prophylactic antibiotics more critical 2, 1
• Cat bite wounds contain an average of 5 different bacterial species per wound, including both aerobic and anaerobic organisms 1
• Pasteurella multocida is the predominant pathogen, found in approximately 75-90% of cat bites 1, 3
• Other common organisms include staphylococci, streptococci, anaerobes (Bacteroides, Fusobacterium, Porphyromonas), and Capnocytophaga 1, 4

First-Line Antibiotic Regimen

Amoxicillin-clavulanate (Augmentin) 875/125 mg twice daily for 5-7 days is recommended by the Infectious Diseases Society of America as first-line treatment due to its excellent coverage of the polymicrobial nature of cat bite infections 1, 4, 5

• This combination maintains 100% susceptibility against P. multocida isolates and covers both aerobic and anaerobic bacteria 3
• Treatment duration is typically 5-7 days for uncomplicated infections but may extend to 3-4 weeks for complications like synovitis or osteomyelitis 1

Alternative Regimens for Penicillin-Allergic Patients

Doxycycline 100 mg twice daily is the preferred alternative, with excellent activity against P. multocida 1

For patients who cannot take doxycycline:

• Fluoroquinolones (ciprofloxacin, levofloxacin, or moxifloxacin) PLUS metronidazole or clindamycin to cover anaerobes 1, 4
• Trimethoprim-sulfamethoxazole PLUS metronidazole as another alternative combination 1

High-Risk Wounds Requiring Prophylaxis

Prophylactic antibiotics are particularly critical for:

• Hand wounds (highest infection risk; NNT = 4 for preventing infection) 1, 6
• Deep puncture wounds, especially over joints or tendons 1
• Fresh wounds presenting within 24 hours 2
• Wounds in immunocompromised patients 1
• Facial, genital, or foot wounds 2

Antibiotics to Avoid

Do not use the following due to poor activity against P. multocida:

• First-generation cephalosporins (e.g., cephalexin) 1
• Penicillinase-resistant penicillins (e.g., dicloxacillin) 1
• Macrolides (e.g., erythromycin) 1
• Clindamycin alone (misses P. multocida) 1

Timing and Wound Management

• Initiate antibiotics within 24 hours of the bite for maximum effectiveness; antibiotics are not recommended if presentation is >24 hours without signs of infection 2
• Thoroughly irrigate the wound with sterile normal saline using a 20-mL or larger syringe 1, 5
• Remove superficial debris and explore for foreign bodies, tendon, or bone involvement 5
• Do not close infected wounds; elevation of the injured area accelerates healing 1

Common Pitfalls to Avoid

• Delayed treatment: Cat bite infections can develop within 12-24 hours, making prompt treatment essential 1
• Inadequate antimicrobial coverage: Using antibiotics with poor P. multocida activity leads to treatment failure 1
• Overlooking hand wounds: These have the highest infection risk and require aggressive prophylaxis 6
• Missing deeper infections: Watch for pain disproportionate to visible inflammation, suggesting periosteal penetration or joint involvement 1
• Relying on topical antibiotics alone: Systemic coverage is necessary for cat bites 7

Special Considerations

• Tetanus prophylaxis should be administered if vaccination status is outdated or unknown 7, 5
• Rabies prophylaxis must be considered even for domestic cats if vaccination status is uncertain 5
• Follow-up within 24 hours (phone or office visit) to ensure improvement 1
• For cat-scratch disease (Bartonella henselae), use azithromycin 500 mg day 1, then 250 mg for 4 additional days 1