What is the first-line antibiotic treatment for cat scratch disease?

First-Line Antibiotic Treatment for Cat Scratch Disease

Azithromycin is the recommended first-line antibiotic treatment for cat scratch disease, with a dosage of 500 mg on day 1 followed by 250 mg for 4 additional days for patients >45 kg. 1

Understanding Cat Scratch Disease

Cat scratch disease (CSD) is an infection caused by Bartonella henselae, a fastidious gram-negative bacillus that is typically acquired from exposure to an infected cat, particularly through scratches or bites. The disease most commonly presents as regional lymphadenopathy that develops approximately 3 weeks after inoculation and typically resolves within 1-6 months 1.

Treatment Recommendations

First-Line Treatment:

• Azithromycin:
  • Adults/children >45 kg: 500 mg on day 1, then 250 mg daily for 4 additional days
  • Children <45 kg: 10 mg/kg on day 1, then 5 mg/kg daily for 4 additional days 1

Alternative Treatments:

• Erythromycin: 500 mg four times daily 1
• Doxycycline: 100 mg twice daily 1
  • Particularly recommended for CNS involvement (with or without rifampin) 2, 1
• Trimethoprim-sulfamethoxazole: Alternative option with approximately 58% efficacy 1

Treatment Duration:

• For typical cat scratch disease: 5 days (azithromycin) or 2 weeks (alternatives)
• For complicated infections or immunocompromised patients: Treatment should be administered for >3 months 2

Special Considerations

Immunocompromised Patients:

• Patients with HIV (especially CD4+ <100 cells/μL) are at high risk for severe Bartonella infections 2, 1
• Doxycycline with or without rifampin is the treatment of choice for severe infections including those involving the CNS 2
• Longer treatment duration (>3 months) is recommended 2

Diabetic Patients:

• May benefit from amoxicillin-clavulanate 875/125 mg orally twice daily for 5-7 days
• Doxycycline 100 mg twice daily for penicillin-allergic patients 1

Treatment Efficacy

In clinical studies, azithromycin has demonstrated more rapid diminution in size of infected lymph nodes compared to placebo 3, 4. Comparative efficacy rates include:

• Rifampin: 87% efficacy
• Ciprofloxacin: 84% efficacy
• Trimethoprim-sulfamethoxazole: 58% efficacy 1

Important Caveats

• Most cases of cat scratch disease in immunocompetent hosts are self-limited and may not require antibiotic treatment 3, 5
• Penicillins and first-generation cephalosporins have no in vivo activity and should not be used for treatment of bartonellosis 2
• Lymphadenopathy may persist for 1-6 months despite appropriate treatment 1
• Clinical reassessment within 24-48 hours is necessary to evaluate response to therapy in patients with worsening lymphangitis and edema 1
• Severe cases with high fever or extensive lymphadenopathy may require hospitalization and IV antibiotics 1

Prevention

• Control of cat flea infestation is crucial as cats are the main reservoir
• Avoid cat scratches, especially from kittens and feral cats
• Immunocompromised individuals should consider the risks of cat ownership 2, 1