What antibiotics are recommended for cat bites?

Antibiotic Treatment for Cat Bites

Amoxicillin-clavulanate is the first-line antibiotic treatment recommended for cat bites due to its excellent coverage against the polymicrobial nature of these infections, particularly Pasteurella multocida which is present in approximately 90% of cat bites. 1

Microbiology of Cat Bite Infections

Cat bites contain an average of 5 different aerobic and anaerobic bacteria per wound, with the following common pathogens:

• Pasteurella species (found in 75% of cat bite wounds) 1
• Staphylococcus aureus (approximately 40% of bites) 1
• Streptococcus species 1
• Anaerobes (Bacteroides, Fusobacterium, Porphyromonas species) 1
• Capnocytophaga canimorsus (particularly concerning in immunocompromised patients) 2

First-Line Antibiotic Recommendations

Oral Therapy (Outpatient)

• Amoxicillin-clavulanate: 875/125 mg twice daily 1
  • Pediatric dose: 25 mg/kg/day of the amoxicillin component in 2 divided doses 1

Intravenous Therapy (For Severe Infections)

• Ampicillin-sulbactam: 1.5-3.0 g every 6-8 hours 1
• Piperacillin-tazobactam: 3.37 g every 6-8 hours 1

Alternative Options for Penicillin-Allergic Patients

• Doxycycline: 100 mg twice daily 1

  • Excellent activity against Pasteurella multocida
  • Not recommended for children under 8 years

• Fluoroquinolone (e.g., moxifloxacin): 400 mg daily 1

  • Provides good coverage for both aerobes and anaerobes
  • Alternative: Ciprofloxacin 500-750 mg twice daily plus metronidazole for anaerobic coverage

• Trimethoprim-sulfamethoxazole: 160-800 mg twice daily plus metronidazole or clindamycin 1

  • Good activity against aerobes but poor against anaerobes

Antibiotics to Avoid

• First-generation cephalosporins (e.g., cephalexin)
• Penicillinase-resistant penicillins (e.g., dicloxacillin)
• Macrolides (e.g., erythromycin)
• Clindamycin alone (poor activity against Pasteurella multocida) 1

Treatment Duration

• For uncomplicated infections: 5-7 days
• For complicated infections (involving bone, joint, or tendon): 2-4 weeks 1

Special Considerations

• Cat bites have a higher infection rate (20-80%) compared to dog bites (3-18%) 3, 2
• Hand wounds from cat bites have the greatest risk of infection and complications 4
• Early antibiotic prophylaxis is crucial, especially for:
  • Deep wounds
  • Wounds on hands, feet, face, or near joints
  • Immunocompromised patients
  • Patients with prosthetic joints or heart valves 1

Important Clinical Pearls

• Wounds should be thoroughly irrigated with sterile normal saline
• Avoid irrigation under pressure as it may spread bacteria into deeper tissues 1
• Surgical debridement may be necessary for necrotic tissue
• Monitor closely for signs of deep infection, especially with hand wounds 5
• Pasteurella multocida remains highly susceptible to penicillins and their derivatives, with susceptibility rates of nearly 100% 3

Remember that prompt treatment is essential, as cat bite infections can progress rapidly and lead to serious complications including osteomyelitis, septic arthritis, and tenosynovitis, particularly in hand injuries.