What antibiotic regimen is recommended for a patient with a cat bite who is allergic to sulfa (sulfonamides) and penicillin?

Antibiotic Treatment for Cat Bite in Patient with Sulfa and Penicillin Allergies

For a patient with a cat bite who is allergic to both sulfa drugs and penicillin, doxycycline 100 mg twice daily is the recommended first-line antibiotic treatment due to its excellent activity against Pasteurella multocida and good coverage of other common pathogens. 1

Microbiology of Cat Bites

• Cat bites have a high infection rate (20-80%) compared to dog bites (3-18%) 2
• Approximately 90% of domestic cats carry Pasteurella multocida in their oral cavity 2
• Cat bites typically contain mixed aerobic and anaerobic bacteria, including:
  • Pasteurella multocida (found in 75% of cat bites) 1
  • Staphylococcus species (found in ~40% of bites) 1
  • Streptococcus species (found in ~40% of bites) 1
  • Anaerobic bacteria including Bacteroides, Fusobacterium, Porphyromonas species 1

First-Line Treatment for Penicillin and Sulfa-Allergic Patients

Doxycycline

• Dosage: 100 mg orally twice daily 1
• Advantages:
  • Excellent activity against Pasteurella multocida 1
  • Good coverage against staphylococci and anaerobes 1
  • Safe alternative for patients with both penicillin and sulfa allergies 1
  • Recommended in the IDSA guidelines specifically for animal bites 1

Alternative Options

Fluoroquinolones

• Ciprofloxacin 500-750 mg orally twice daily 1
  • Good activity against P. multocida 1
  • May miss some anaerobes, consider adding metronidazole 1

Clindamycin

• Clindamycin 300 mg orally three times daily 1
  • Good activity against staphylococci, streptococci, and anaerobes 1
  • Important limitation: Misses P. multocida, which is present in 75% of cat bites 1
  • If using clindamycin, consider combination with a fluoroquinolone 1

Azithromycin

• Consider for patients who cannot tolerate doxycycline or fluoroquinolones 3
• Has shown efficacy in cat scratch disease (also caused by cat-associated bacteria) 1, 4

Duration of Therapy

• For uncomplicated wounds: 5-7 days 5
• For complicated infections (deep structure involvement, osteomyelitis):
  • 3-4 weeks for synovitis 1
  • 4-6 weeks for osteomyelitis 1

Special Considerations

• Hand wounds are at higher risk for infection and complications 1, 6
  • Prophylactic antibiotics significantly reduce infection risk in hand bites (NNT = 4) 6
• Immunocompromised patients may require broader coverage and longer treatment duration 1
• First-generation cephalosporins (cephalexin), macrolides (erythromycin), and penicillinase-resistant penicillins (dicloxacillin) have poor activity against P. multocida and should be avoided 1

Wound Management

• Thorough wound cleaning and irrigation with normal saline is essential 5
• Evaluate for tendon, bone, or joint involvement 5
• Consider delayed closure for wounds >8 hours old, except for facial wounds 1
• Elevate the affected area to reduce swelling 1

Monitoring and Follow-up

• Monitor for signs of worsening infection (increasing pain, swelling, redness, fever) 1
• Pain disproportionate to injury near bone or joint suggests possible periosteal penetration 1
• Follow up within 24-48 hours for high-risk wounds (hand, deep punctures) 5