What is the recommended oral antibiotic for a cat scratch?

Oral Antibiotic for Cat Scratch

Distinguish Between Two Different Clinical Scenarios

For a simple cat scratch wound (prophylaxis or early infection), use amoxicillin-clavulanate 875/125 mg twice daily as first-line therapy. 1

For cat scratch disease (lymphadenopathy from Bartonella henselae), use azithromycin 500 mg on day 1, then 250 mg daily for 4 additional days. 1, 2

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Cat Scratch Wound (Prophylaxis/Treatment of Wound Infection)

First-Line Therapy

• Amoxicillin-clavulanate 875/125 mg orally twice daily is the recommended first-line antibiotic for cat scratch wounds, providing optimal coverage against Pasteurella multocida (present in 60-80% of cat oral flora), staphylococci, streptococci, and anaerobes. 1, 3
• Prophylactic antibiotics are particularly important for deep wounds, wounds on hands/feet/face/near joints, and in immunocompromised patients, as infection rates range from 10-20% for scratches and 30-50% for bites. 1
• Treatment duration is typically 7-10 days for uncomplicated infections. 3

Alternative Regimens for Penicillin Allergy

• Doxycycline 100 mg orally twice daily is the preferred alternative for penicillin-allergic patients, with excellent activity against P. multocida. 1, 3
• Fluoroquinolones (ciprofloxacin 500-750 mg twice daily or levofloxacin 750 mg daily) provide good Pasteurella coverage but miss MRSA and some anaerobes. 1, 3
• Trimethoprim-sulfamethoxazole plus metronidazole can be used for combined aerobic/anaerobic coverage. 1

Critical Antibiotics to AVOID

• Do NOT use first-generation cephalosporins (cephalexin, cefazolin) or penicillinase-resistant penicillins (dicloxacillin, nafcillin) as monotherapy, as they have poor activity against P. multocida, the most common pathogen in cat scratches. 3
• Clindamycin should not be used as monotherapy for cat scratches due to poor Pasteurella coverage, though it can be combined with a fluoroquinolone if MRSA coverage is needed. 1

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Cat Scratch Disease (Bartonella henselae Lymphadenopathy)

Clinical Recognition

• Cat scratch disease typically presents with a papule or pustule 3-30 days after exposure, followed by regional lymphadenopathy approximately 3 weeks after inoculation. 2
• Lymphadenopathy generally resolves within 1-6 months spontaneously, with suppuration occurring in about 10% of cases. 2
• Most cases in immunocompetent patients are self-limited and do not require antibiotics, but treatment accelerates resolution. 4, 5, 6

First-Line Treatment

• Azithromycin is the first-line antibiotic for cat scratch disease: 500 mg on day 1, followed by 250 mg daily for 4 additional days (for patients >45 kg). 1, 2, 7
• For patients <45 kg: 10 mg/kg on day 1, then 5 mg/kg daily for 4 additional days. 1, 2
• This recommendation is based on a placebo-controlled study demonstrating more rapid lymph node regression with azithromycin compared to no treatment. 4, 2

Alternative Regimens

• Doxycycline 100 mg orally twice daily is an alternative if azithromycin is contraindicated. 2
• Erythromycin 500 mg orally four times daily is another alternative, and is the preferred option for pregnant women (tetracyclines are contraindicated in pregnancy). 2

When Treatment is Strongly Recommended

• Immunocompromised patients (especially HIV with CD4+ <100 cells/µL) require treatment due to risk of disseminated disease, bacillary angiomatosis, and peliosis hepatis. 2
• Extranodal or disseminated disease requires treatment. 2
• For severe manifestations (CNS involvement, hepatosplenic disease), doxycycline with or without rifampin is preferred, with treatment duration extending beyond 3 months. 2

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Special Considerations and Pitfalls

Diabetic Patients

• Diabetic patients with infected cat scratches require more aggressive treatment (1-2 weeks minimum, up to 3-4 weeks if extensive or slow to resolve) due to impaired immune response and delayed wound healing. 1
• Optimal wound care including debridement and off-loading is essential in addition to antibiotics. 1

Hand Wounds

• Hand wounds have the highest infection risk and complication rate (18% develop complications including tendosynovitis, septic arthritis, osteomyelitis), requiring prompt treatment and close follow-up. 3
• If deep space infection or abscess is suspected, surgical consultation for incision and drainage is mandatory. 3

Immunocompromised Patients

• In advanced HIV (CD4+ <100 cells/µL), up to 25% of culture-positive patients may never develop antibodies, making serologic testing unreliable. 2
• Consider Bartonella in any HIV patient with unexplained fever and CD4+ <100 cells/µL. 2
• Long-term suppression with erythromycin or doxycycline is recommended until CD4+ >200 cells/µL for >6 months. 2

Pregnancy

• Erythromycin is the only safe option for pregnant women; avoid tetracyclines (doxycycline) completely. 2

Wound Care Essentials

• Thoroughly cleanse all cat scratches with sterile normal saline to remove debris. 1
• Evaluate tetanus immunization status and update if needed. 1
• Consider rabies risk assessment for scratches from unknown or feral cats. 1
• Advise patients to return if signs of infection develop (increasing pain, redness, swelling, purulent drainage, fever). 1