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 treatment recommended for cat bite wounds due to its excellent coverage against Pasteurella multocida and other common pathogens found in cat bites. 1

Microbiology and Infection Risk

Cat bites have a high risk of infection due to:

• Presence of Pasteurella multocida in >50% of cat bite wounds
• Deep puncture wounds from cat teeth that can inoculate bacteria into tissues
• Multiple organisms typically present (average of 5 different aerobic and anaerobic bacteria per wound)
• Common pathogens include:
  • Pasteurella multocida (predominant concern)
  • Staphylococcus species
  • Streptococcus species
  • Anaerobes (Bacteroides, Fusobacterium, Porphyromonas)
  • Bartonella henselae (cat scratch disease)

First-Line Antibiotic Options

1. Oral therapy (outpatient):

   • Amoxicillin-clavulanate: 875/125 mg twice daily 1

2. Intravenous therapy (for severe infections):

   • Ampicillin-sulbactam: 1.5-3.0 g every 6-8 hours
   • Piperacillin-tazobactam: 3.37 g every 6-8 hours

Alternative Options for Penicillin-Allergic Patients

• Doxycycline: 100 mg twice daily (excellent activity against P. multocida) 1
• Fluoroquinolone + Metronidazole:
  • Ciprofloxacin 500-750 mg twice daily or Moxifloxacin 400 mg daily
  • Plus Metronidazole 250-500 mg three times daily (for anaerobic coverage)
• Clindamycin + Fluoroquinolone: For patients who cannot take doxycycline

Special Considerations

Cat Scratch Disease

• If cat scratch disease is suspected (lymphadenopathy developing 3 weeks after scratch):
  • Azithromycin (preferred): 500 mg on day 1, then 250 mg daily for 4 more days 1

Hand Infections

• Cat bites to the hand have the highest risk of infection 2
• Require more aggressive treatment and closer follow-up
• Consider early surgical consultation if:
  • Signs of tenosynovitis
  • Joint involvement
  • Deep space infection
  • Rapidly progressing infection 3

Duration of Therapy

• Uncomplicated infections: 5-7 days
• Complicated infections (deeper structures involved): 10-14 days

Treatment Algorithm

1. Initial assessment:

   • Determine wound depth, location, and time since injury
   • Check for signs of established infection (erythema, swelling, purulence)

2. Wound management:

   • Copious irrigation with normal saline
   • Debridement of devitalized tissue
   • Do not primarily close puncture wounds

3. Antibiotic selection:

   • For fresh, uninfected wounds: Prophylactic antibiotics recommended, especially for:

     • Hand wounds
     • Deep puncture wounds
     • Immunocompromised patients
     • Wounds near joints or tendons

   • For established infections: Start empiric therapy immediately while cultures are pending

4. Follow-up:

   • Re-evaluate within 24-48 hours for all hand wounds
   • Consider hospitalization for:
     • Severe or rapidly progressing infections
     • Systemic symptoms
     • Immunocompromised patients
     • Failed outpatient therapy

Common Pitfalls to Avoid

1. Underestimating cat bites: Even small puncture wounds can cause serious infections due to deep inoculation of bacteria.

2. Delayed treatment: Cat bite infections can progress rapidly, especially on the hand. Early antibiotic therapy is crucial.

3. Inadequate coverage: Failing to cover P. multocida can lead to treatment failure. Avoid using first-generation cephalosporins or dicloxacillin alone as they have poor activity against this organism.

4. Missing tendon or joint involvement: Deep structures can be affected even with seemingly minor external wounds.

5. Overlooking cat scratch disease: Consider this diagnosis when regional lymphadenopathy develops weeks after a scratch or bite.