What is the best antibiotic for a cat bite?

Best Antibiotic for Cat Bite

Amoxicillin-clavulanate 875/125 mg twice daily is the first-line antibiotic for cat bite wounds, as recommended by the Infectious Diseases Society of America and supported by clinical studies. 1, 2

Why Amoxicillin-Clavulanate is First-Line

• Cat bites have an exceptionally high infection rate (20-80%) compared to dog bites (3-18%), making antibiotic coverage critical 3, 4

• Pasteurella multocida is isolated from approximately 75% of cat bite wounds and is the predominant pathogen requiring coverage 1, 2

• Cat bite wounds contain an average of 5 different bacterial species per wound, including both aerobic and anaerobic bacteria 2

• Anaerobic bacteria are present in 65% of cat bite infections, often concurrently with P. multocida, requiring broad-spectrum coverage 1, 2

• Staphylococci and streptococci are found in approximately 40% of cat bites, necessitating coverage beyond just Pasteurella 2

• Amoxicillin-clavulanate provides excellent in vitro coverage against the entire pathogenic flora found in cat bites 5

• Studies demonstrate that P. multocida maintains 100% susceptibility to amoxicillin-clavulanate, confirming its continued reliability 3

Alternative Oral Options (When Amoxicillin-Clavulanate Cannot Be Used)

For penicillin-allergic patients:

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

• Fluoroquinolones are alternatives with good activity against P. multocida: 1

  • Moxifloxacin 400 mg daily (best fluoroquinolone option with superior anaerobic coverage) 5
  • Levofloxacin 750 mg daily
  • Ciprofloxacin 500-750 mg twice daily
  • Note: Fluoroquinolones may not adequately cover MRSA and some anaerobes 1

Antibiotics to AVOID for Cat Bites

The following antibiotics have poor activity against P. multocida and should NOT be used: 1, 2

• First-generation cephalosporins (e.g., cephalexin)
• Penicillinase-resistant penicillins (e.g., dicloxacillin) as monotherapy
• Macrolides (e.g., erythromycin, azithromycin)
• Clindamycin as monotherapy (despite FDA approval for skin infections, it completely misses P. multocida) 2, 6

Intravenous Options for Severe Infections

Consider hospitalization and IV therapy for: 1

• Evidence of systemic infection
• Rapidly progressing infection despite oral antibiotics
• Deep tissue involvement (septic arthritis, osteomyelitis, tendonitis)
• Immunocompromised hosts
• Need for surgical intervention

IV antibiotic options: 1, 2

• Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours
• Piperacillin-tazobactam 3.37 g every 6-8 hours
• Second-generation cephalosporins (e.g., cefoxitin 1 g every 6-8 hours)
• Carbapenems (ertapenem, imipenem, meropenem)

Treatment Duration for Complications

• Osteomyelitis: 4-6 weeks of antibiotic therapy 2
• Septic arthritis/synovitis: 3-4 weeks of antibiotic therapy 2

Critical Clinical Pitfalls

• Cat bites to the hand have the greatest risk of infection and warrant aggressive treatment 7

• Puncture wounds (typical of cat bites due to their sharp teeth) have higher infection rates than lacerations 8

• Infected wounds should NOT be closed; only cosmetically favorable uninfected wounds may be primarily closed 2

• All patients require thorough wound cleansing with sterile normal saline and removal of superficial debris 2

• Outpatients must be followed up within 24 hours either by phone or office visit to assess for progression 2

• Tetanus prophylaxis should be administered if vaccination status is outdated or unknown 2, 7

• Rabies prophylaxis should be considered even for domestic cats if vaccination status is unknown 8