What is the treatment for cat bite associated cellulitis?

Treatment of Cat Bite Associated Cellulitis

For cat bite associated cellulitis, amoxicillin-clavulanic acid is the first-line antibiotic treatment due to its excellent coverage against Pasteurella multocida and anaerobes. 1

Microbiology and Pathophysiology

Cat bites have a high infection rate (30-50%) compared to other animal bites 2. The predominant pathogens include:

• Pasteurella multocida (primary pathogen, present in ~90% of cats' oral cavities) 3
• Anaerobes (Fusobacterium, Bacteroides, Porphyromonas, Prevotella species)
• Streptococcus species
• Staphylococcus aureus (including potential MRSA)
• Capnocytophaga canimorsus

Treatment Algorithm

1. Initial Wound Management

• Thoroughly irrigate wound with sterile saline or water to remove bacteria and debris
• Debride any necrotic tissue
• Assess for foreign bodies or deep structure involvement (tendons, joints, bones)
• Leave puncture wounds open to heal by secondary intention 1

2. Antibiotic Therapy

For Outpatient Treatment (Mild to Moderate Infection):

• First-line: Amoxicillin-clavulanic acid (875/125 mg twice daily) 2, 1
• Duration: 7-14 days 1

For Penicillin-Allergic Patients:

• Alternative options:
  • Doxycycline 100 mg twice daily 1
  • Fluoroquinolone (ciprofloxacin or levofloxacin) plus metronidazole 1

For Inpatient Treatment (Severe Infection):

• First-line: Ampicillin-sulbactam IV 1
• Alternative: Piperacillin-tazobactam IV (for severe skin and skin structure infections) 4
• Duration: 7-14 days, extended to 3-4 weeks for osteomyelitis or septic arthritis 1

3. Indications for Hospitalization

• Systemic symptoms (fever, hypotension)
• Rapidly progressing infection
• Hand infections (high risk for complications)
• Immunocompromised patients
• Deep tissue involvement (joints, tendons, bones)
• Failed outpatient therapy 1

Special Considerations

Hand Infections

Cat bites to the hand require special attention due to:

• Higher risk of infection progression
• Proximity of tendons, joints, and bones
• Consider early surgical consultation for deep hand wounds 1, 5

High-Risk Patients

• Immunocompromised patients
• Elderly patients
• Asplenic patients (at risk for overwhelming Capnocytophaga canimorsus sepsis)
• Cirrhotic patients (at risk for severe infection)
• These patients may require more aggressive therapy and closer monitoring 1

Monitoring and Follow-up

• Follow-up within 24-48 hours to assess response
• Monitor for signs of worsening infection (increasing erythema, pain, swelling, purulent discharge)
• Consider inflammatory markers (CRP, ESR) if clinical examination is equivocal 1

Common Pitfalls to Avoid

1. Using inadequate antibiotics: First-generation cephalosporins, penicillinase-resistant penicillins, macrolides, and clindamycin alone have poor activity against Pasteurella multocida and should be avoided 1

2. Delayed treatment: Cat bite infections can progress rapidly, with cellulitis developing within 12-24 hours post-bite 5

3. Premature wound closure: Puncture wounds should be left open to prevent abscess formation 1

4. Overlooking deep structure involvement: Particularly in hand wounds, where tendons, joints, and bones are close to the surface

5. Failing to consider rabies and tetanus prophylaxis: Ensure tetanus vaccination is current and evaluate need for rabies prophylaxis 1

By following this treatment approach, cat bite associated cellulitis can be effectively managed to prevent serious complications such as bacteremia, sepsis, osteomyelitis, and joint infections 6, 7.