What antibiotics are recommended for the treatment of a cat scratch disease?

Antibiotic Treatment for Cat Scratch Disease

For cat scratch disease, azithromycin is the recommended antibiotic treatment, with a dosing protocol of 500 mg on day 1 followed by 250 mg for 4 additional days for patients weighing over 45 kg, or 10 mg/kg on day 1 and 5 mg/kg for 4 more days for patients weighing less than 45 kg. 1

Clinical Presentation and Diagnosis

Cat scratch disease is caused by Bartonella henselae and typically presents as:

• A papule or pustule developing 3-30 days after a cat scratch or bite
• Regional lymphadenopathy occurring approximately 3 weeks after inoculation
• Lymph nodes that may persist for 1-6 months, with suppuration in about 10% of cases
• Extranodal disease (CNS, liver, spleen, bone, lung) in ≤2% of cases 1

Diagnosis is supported by:

• History of cat exposure
• Serologic testing (high titers >1:256 of IgG antibodies to B. henselae)
• PCR testing when available
• Warthin-Starry silver stain of infected lymph node tissue 1

Treatment Algorithm

1. Typical Cat Scratch Disease (Immunocompetent Host)

• First-line therapy: Azithromycin 1

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

• Alternative options (if azithromycin cannot be used):

  • Doxycycline 100 mg twice daily 2
  • Ciprofloxacin 2
  • Trimethoprim-sulfamethoxazole 2
  • Rifampin 2

2. Bacillary Angiomatosis (Immunocompromised Host)

• First-line therapy:
  • Erythromycin 500 mg four times daily for 2 weeks to 2 months, OR
  • Doxycycline 100 mg twice daily for 2 weeks to 2 months 1

3. Disseminated Disease

For patients with severe or disseminated disease (hepatosplenic involvement, neuroretinitis, osteomyelitis):

• Consider combination therapy with azithromycin plus rifampin 3
• Longer duration of therapy (2-4 weeks) may be necessary 3

Evidence Supporting Azithromycin

The recommendation for azithromycin is based on a prospective, randomized, double-blind, placebo-controlled study that demonstrated:

• 7 of 14 azithromycin-treated patients showed 80% decrease in lymph node volume within 30 days
• Only 1 of 15 placebo-treated patients showed similar improvement (p=0.026) 4

This is the strongest evidence available for antibiotic efficacy in cat scratch disease, making azithromycin the treatment of choice.

Important Clinical Considerations

• Most cases are self-limited and may not require antibiotic treatment 5, but treatment speeds recovery and reduces lymph node volume more quickly 1, 4

• Treatment is particularly indicated for:

  • Severe lymphadenopathy
  • Systemic symptoms
  • Immunocompromised patients
  • Extranodal manifestations

• Monitoring: Follow lymph node size; improvement should be seen within 30 days of treatment initiation 4

• Pitfalls to avoid:

  1. Failure to consider cat scratch disease in the differential diagnosis of regional lymphadenopathy
  2. Overlooking the need for more aggressive therapy in immunocompromised patients
  3. Missing disseminated disease manifestations that may require longer treatment
  4. Unnecessary surgical drainage of lymph nodes (unless diagnostic sampling is needed)

Remember that while most cases of cat scratch disease are self-limited, azithromycin treatment has been proven to accelerate recovery and is therefore recommended, especially for patients with significant lymphadenopathy or systemic symptoms.