What is the recommended treatment for a patient with an infected cat scratch, potentially developing cat-scratch disease, considering possible immunocompromised status or allergy history?

Treatment for Infected Cat Scratch

For an infected cat scratch, immediately cleanse the wound thoroughly with sterile saline and initiate amoxicillin-clavulanate 875/125 mg twice daily as first-line therapy to prevent progression to serious infection. 1

Initial Wound Management

Perform thorough wound cleansing with sterile normal saline to remove superficial debris and reduce bacterial load. 1 Deeper debridement is typically unnecessary unless significant devitalized tissue is present. 1

Immediate Risk Assessment

• Cat scratches carry a 10-20% infection risk, substantially lower than cat bites (30-50%), but still warrant prophylactic treatment in high-risk scenarios. 1
• Prophylactic antibiotics are mandatory for:
  • Deep wounds 1
  • Wounds on hands, feet, face, or near joints 1
  • Immunocompromised patients 1
• Update tetanus immunization if needed and assess rabies risk for scratches from unknown or feral cats. 1

Antibiotic Selection for Infected Cat Scratch

First-Line Therapy

Amoxicillin-clavulanate is the preferred antibiotic because it provides optimal coverage against Pasteurella multocida and other common pathogens from cat scratches. 1 This is distinct from cat scratch disease (Bartonella infection), which develops weeks later.

Alternative Regimens for Penicillin Allergy

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

Critical pitfall: Clindamycin should NOT be used as monotherapy for cat scratches because it lacks Pasteurella coverage, despite good activity against staphylococci and anaerobes. 1

Treatment Duration

• Standard duration: 1-2 weeks for mild soft tissue infections 1
• Extended duration: 3-4 weeks if infection is extensive, resolving slowly, or patient has severe peripheral artery disease 1
• Diabetic patients require more aggressive treatment due to impaired immune response and delayed wound healing 1

Distinguishing Cat Scratch Disease (Bartonella henselae)

If the patient develops regional lymphadenopathy 3 weeks after the scratch, this suggests progression to cat scratch disease rather than simple wound infection. 2, 3

Treatment for Cat Scratch Disease

Azithromycin is first-line treatment for cat scratch disease:

• Patients >45 kg: 500 mg on day 1, then 250 mg daily for 4 additional days 2
• Patients <45 kg: 10 mg/kg on day 1, then 5 mg/kg daily for 4 additional days 2

Alternative regimens if azithromycin is contraindicated:

• Doxycycline 100 mg twice daily for 10-14 days 1
• Erythromycin 500 mg four times daily 2

The recommendation for azithromycin is based on placebo-controlled evidence showing more rapid reduction in lymph node size. 2 However, most immunocompetent patients with cat scratch disease will recover without antibiotics, as the condition is typically self-limited. 2, 4, 5

Special Populations

Immunocompromised Patients

Immunocompromised patients require aggressive treatment because they risk disseminated disease including bacillary angiomatosis, peliosis hepatis, and CNS involvement. 2

• For HIV patients with CD4+ <100 cells/µL: Consider Bartonella in any unexplained fever 2
• Extended therapy >3 months with erythromycin or doxycycline is recommended for bacillary angiomatosis, peliosis hepatis, or CNS involvement 2
• Long-term suppression with erythromycin or doxycycline until CD4+ >200 cells/µL for >6 months 1
• Up to 25% of HIV patients with advanced disease may never develop antibodies despite active infection 2, 1

For severe cases with hepatosplenic involvement: Gentamicin has shown 73% efficacy with rapid response within 48 hours. 2

Pregnant Women

Erythromycin is the only safe option for pregnant women—tetracyclines (doxycycline) are completely contraindicated. 2, 1

Pediatric Patients

Weight-based dosing applies for children:

• Azithromycin: 10 mg/kg day 1, then 5 mg/kg for 4 days (for cat scratch disease) 2
• Doxycycline: 2.2 mg/kg twice daily, maximum 100 mg per dose, for 10-14 days (for cat scratch disease) 1
• Fluoroquinolones should be used with extreme caution in children and only if no alternatives exist 1

Follow-Up and Monitoring

Instruct patients to return immediately if signs of infection develop or worsen:

• Increasing pain, redness, swelling 1
• Purulent drainage 1
• Fever 1

Monitor for serious complications, especially with hand wounds: septic arthritis, osteomyelitis, or tendonitis. 1

For diabetic patients: Early and careful follow-up is essential to ensure treatment effectiveness, with optimal wound care including debridement of necrotic tissue and off-loading of pressure. 1

Prevention Counseling

Advise patients to:

• Avoid rough play with cats and situations where scratches are likely 2
• Promptly wash any cat-associated wounds 2
• Implement comprehensive flea control for cats (fleas transmit Bartonella between cats) 2
• Not allow cats to lick open wounds 2
• Choose cats >1 year old in good health if acquiring a new pet 2

For severely immunosuppressed persons: Consider the risks of cat ownership carefully, as they are at higher risk for Bartonella infection. 6, 2