What is the treatment for hand cellulitis caused by a cat scratch?

Treatment of Hand Cellulitis from Cat Scratch

For hand cellulitis following a cat scratch, you must use an antibiotic that covers Pasteurella multocida (the primary pathogen), specifically amoxicillin-clavulanate or a fluoroquinolone, NOT the standard cellulitis regimens of cephalexin or dicloxacillin which are ineffective against Pasteurella species. 1

Key Pathogen Recognition

Cat scratches and bites cause cellulitis from Pasteurella multocida (especially P. multocida) or Capnocytophaga canimorsus, not the typical streptococci or staphylococci that cause routine cellulitis. 1

• Cats are the source in 60-80% of Pasteurella infections, with rapid onset cellulitis appearing within 12-24 hours of injury 2, 3
• The infection characteristically presents with rapidly developing erythema, warmth, tenderness, and frequently purulent or serosanguineous drainage 2, 4
• This is distinct from typical cellulitis which develops more slowly over days 1

Critical Treatment Algorithm

First-Line Antibiotic Selection

Penicillin-based therapy is the treatment of choice for Pasteurella multocida:

• Oral therapy: Amoxicillin-clavulanate is preferred as it covers Pasteurella, streptococci, and S. aureus 2, 3, 4
• Parenteral therapy (for severe cases): Ampicillin-sulbactam or a penicillinase-resistant penicillin plus coverage for Pasteurella 1, 3
• Penicillin allergy: Fluoroquinolones (ciprofloxacin or levofloxacin) or doxycycline are alternatives 3, 5

Antibiotics to AVOID

Do NOT use standard cellulitis regimens:

• Cephalexin, dicloxacillin, and first-generation cephalosporins are INEFFECTIVE against Pasteurella 1, 2
• While guidelines recommend these for typical cellulitis, cat scratches require different coverage 1

Surgical Management

Immediate surgical drainage is mandatory in addition to antibiotics:

• All wounds with serosanguineous or purulent drainage require surgical drainage 2
• 92% of cat wounds penetrate deeply through skin, increasing risk of deep tissue infection and osteomyelitis 2
• Hand infections are particularly dangerous due to risk of tenosynovitis, septic arthritis, and osteomyelitis 2, 3

Treatment Duration and Monitoring

• Standard duration is 5-10 days for uncomplicated cases 1, 2
• Monitor closely for complications including abscess formation, tenosynovitis, septic arthritis, and osteomyelitis which commonly involve fingers and hands after cat bites 3
• Patients typically present 12-72 hours after injury; earlier presentation (12-24 hours) strongly suggests Pasteurella 2

Important Caveats

Distinguish from Cat Scratch Disease (Bartonella henselae):

• Cat scratch disease presents with papule/pustule 3-30 days post-exposure followed by regional lymphadenopathy at 3 weeks 6
• This is treated with azithromycin (500 mg day 1, then 250 mg for 4 days if >45 kg) 6
• Acute cellulitis within 12-48 hours is Pasteurella, NOT Bartonella 6, 2

Elevation of the affected hand is essential adjunctive therapy to promote drainage of edema and inflammatory substances 1