What is the recommended treatment for a patient with a cat bite, considering potential infection risk and underlying medical conditions, such as compromised immune systems or unknown tetanus (tetanus toxoid) vaccination status?

Cat Bite Treatment

Cat bites require immediate wound irrigation with sterile saline, prophylactic amoxicillin-clavulanate 875/125 mg twice daily for 3-5 days (or treatment for 7-14 days if already infected), tetanus prophylaxis if status is outdated or unknown, and rabies risk assessment based on the animal's vaccination status and local epidemiology. 1, 2

Immediate Wound Management

All cat bite wounds must be thoroughly cleansed with sterile normal saline to remove debris and reduce bacterial load 1. This mechanical cleansing is critical because it markedly reduces infection risk even without antibiotics 1.

• Irrigate copiously using a 20-mL or larger syringe, but avoid high-pressure irrigation that may drive bacteria deeper into tissues 3
• Remove superficial debris only; deeper debridement is usually unnecessary and may impair healing 1, 2
• Do not close infected wounds 1
• For fresh wounds (<8 hours), primary closure is controversial; use Steri-Strips for approximation with delayed closure preferred 1
• Facial wounds are an exception and may be closed primarily by a plastic surgeon after meticulous irrigation and prophylactic antibiotics 1, 4

Antibiotic Therapy

First-Line Treatment

Amoxicillin-clavulanate 875/125 mg twice daily is the first-line antibiotic for both prophylaxis and treatment 1, 2, 5, 4, 3. This provides optimal coverage against Pasteurella multocida (present in 50-80% of cat bites), Staphylococcus aureus, streptococci, and anaerobes 6, 5, 4.

Indications for Prophylactic Antibiotics

Prophylaxis is recommended for: 1, 2, 3

• All cat bites (30-50% infection rate, highest among animal bites) 1, 2
• Deep puncture wounds (cats have sharp teeth that inoculate bacteria deeply) 5, 7
• Hand, foot, face, or near-joint wounds 2, 3
• Immunocompromised patients 1, 2

Penicillin-Allergic Patients

For penicillin allergy: 1, 2

• Doxycycline 100 mg twice daily (excellent Pasteurella activity) 2
• Fluoroquinolones: ciprofloxacin 500-750 mg twice daily or levofloxacin 750 mg daily 1, 2
• Trimethoprim-sulfamethoxazole plus metronidazole (for combined aerobic/anaerobic coverage) 1, 2

Avoid clindamycin monotherapy as it lacks Pasteurella coverage despite good activity against staphylococci and anaerobes 2.

Treatment Duration

• Prophylaxis: 3-5 days 2
• Established infection: 7-14 days 2
• Complicated infections (septic arthritis): 3-4 weeks 1
• Osteomyelitis: 4-6 weeks 1

Tetanus Prophylaxis

Administer tetanus toxoid 0.5 mL intramuscularly if vaccination status is outdated or unknown 1. This is mandatory for all bite wounds 1.

Rabies Risk Assessment

Domestic Cats

A healthy domestic cat should be confined and observed for 10 days 1. If the animal remains healthy during this period, it was not infectious at the time of the bite 1.

• If the cat develops signs of rabies during observation, immediately initiate postexposure prophylaxis and euthanize the animal for testing 1
• Stray or unwanted cats should be euthanized immediately and tested 1

Rabies Postexposure Prophylaxis

If indicated, administer: 1

• Human rabies immune globulin (HRIG) on day 0 (infiltrate around wound if possible, remainder intramuscularly at distant site)
• Rabies vaccine on days 0,3,7, and 14 1, 3
• Consult local health department for risk assessment, especially for feral cats or in rabies-endemic areas 1, 2

High-Risk Situations and Complications

Hand Wounds

Hand wounds carry the greatest infection risk and require aggressive management 5. Pain disproportionate to injury near bone or joint suggests periosteal penetration 1.

• Evaluate for tendon or bone involvement 3
• Consider early surgical consultation 1
• Elevate the injured hand to accelerate healing 1, 2

Immunocompromised Patients

Diabetic and immunocompromised patients require more aggressive treatment 2:

• Treat for 1-2 weeks minimum, extending to 3-4 weeks if extensive or slow-healing 2
• Lower threshold for hospitalization and IV antibiotics 1
• Monitor for atypical presentations including bacillary angiomatosis (Bartonella henselae) 2

Warning Signs Requiring Urgent Evaluation

Seek immediate surgical consultation for: 2

• Deep abscess formation
• Extensive necrosis or necrotizing fasciitis
• Septic arthritis or osteomyelitis
• Systemic signs: fever, lymphangitis, bacteremia 6

Follow-Up

All patients should be reassessed within 24 hours (by phone or office visit) 1. Instruct patients to return immediately for: 2

• Increasing pain, redness, or swelling
• Purulent drainage
• Fever or systemic symptoms
• Decreased range of motion

Critical Pitfalls to Avoid

• Never use first-generation cephalosporins or penicillin alone (poor Pasteurella coverage due to β-lactamase production) 1
• Do not underestimate cat bites despite appearing minor (deep inoculation with high infection rates) 5, 7
• Do not delay antibiotics for high-risk wounds (hand, deep punctures, immunocompromised) 2, 3
• Do not forget rabies assessment even for domestic animals (many are unvaccinated) 3