What is the treatment for a local infection resulting from a cat scratch?

Treatment of Local Cat Scratch Infection

For a local infection from a cat scratch, start amoxicillin-clavulanate 875/125 mg twice daily as first-line therapy after thorough wound cleansing with sterile normal saline. 1

Immediate Wound Management

• Cleanse the wound thoroughly with sterile normal saline to remove superficial debris 1
• Deeper debridement is usually unnecessary unless significant devitalized tissue is present 1
• Elevate the injured body part if swollen to accelerate healing 1
• Evaluate and update tetanus immunization status 1
• Consider rabies risk assessment for scratches from unknown or feral cats 1

Antibiotic Selection Algorithm

First-Line Therapy

• Amoxicillin-clavulanate is the recommended first-line oral therapy, providing optimal coverage against Pasteurella multocida and other common pathogens from cat scratches 1
• This is particularly important for deep wounds, wounds on hands/feet/face/near joints, or in immunocompromised patients 1
• Cat scratches carry approximately 10-20% infection risk, making prophylactic antibiotics appropriate for high-risk wounds 1

Penicillin-Allergic Patients

• Doxycycline 100 mg twice daily (adults) is the preferred alternative, with excellent activity against Pasteurella multocida 1
• Fluoroquinolones (ciprofloxacin 500-750 mg twice daily or levofloxacin 750 mg daily) provide good Pasteurella coverage 1
• Trimethoprim-sulfamethoxazole plus metronidazole can be used for combined aerobic/anaerobic coverage 1

Critical Caveat About Clindamycin

• Clindamycin should NOT be used as monotherapy for cat scratches due to poor Pasteurella coverage, despite having good activity against staphylococci, streptococci, and anaerobes 1
• If MRSA coverage is needed along with Pasteurella coverage, combine clindamycin with a fluoroquinolone rather than using it alone 1

Treatment Duration

• For uncomplicated local infections in immunocompetent patients, treat for the standard course appropriate to the antibiotic chosen 1
• For diabetic patients with mild soft tissue infections, administer antibiotics for 1-2 weeks 1
• Consider extending treatment to 3-4 weeks if the infection is extensive, resolving slowly, or the patient has severe peripheral artery disease 1

Special Populations

Diabetic Patients

• Diabetic patients require more aggressive treatment due to impaired immune response and delayed wound healing 1
• Provide optimal wound care including proper cleansing, debridement of necrotic tissue, and off-loading of pressure 1
• Evaluate arterial supply and consider revascularization when indicated 1
• Seek urgent surgical consultation for deep abscess, extensive necrosis, or necrotizing fasciitis 1

Immunocompromised Patients

• Be vigilant for atypical presentations including bacillary angiomatosis 1
• These patients require more thorough evaluation and potentially longer treatment courses 1

Distinguishing Local Infection from Cat Scratch Disease

This is a critical distinction that affects treatment choice:

• Local wound infection (cellulitis, abscess at scratch site) requires amoxicillin-clavulanate or alternatives as above 1
• Cat scratch disease (Bartonella henselae infection with lymphadenopathy developing 3 weeks post-scratch) requires azithromycin: 500 mg day 1, then 250 mg for 4 days (>45 kg) or 10 mg/kg day 1, then 5 mg/kg for 4 days (<45 kg) 2, 1

Monitoring and Follow-Up

• Advise patients to return if signs of infection develop or worsen: increasing pain, redness, swelling, purulent drainage, or fever 1
• Monitor for complications such as septic arthritis, osteomyelitis, or tendonitis, especially with hand wounds 1
• Early and careful follow-up is essential to ensure treatment effectiveness 1

Common Pitfalls to Avoid

• Do not use penicillins or first-generation cephalosporins alone—they lack adequate Pasteurella coverage 3
• Do not use clindamycin as monotherapy for animal scratches 1
• Do not overlook the need for prophylactic antibiotics in high-risk wounds (deep, hand/foot/face location, immunocompromised host) 1
• Do not confuse simple local infection with cat scratch disease—the latter presents with regional lymphadenopathy weeks after inoculation and requires different treatment 2, 3