What is the recommended treatment for infections caused by cat bites versus scratches?

Treatment of Infections from Cat Bites versus Scratches

Cat bites require immediate medical attention and antibiotic treatment, while cat scratches generally need thorough cleaning but antibiotics only if signs of infection develop or in immunocompromised patients.

Cat Bite Infections

Immediate Management

• Clean wound thoroughly with sterile normal saline 1
• Remove superficial debris (deeper debridement usually unnecessary) 1
• Elevate the injured body part, especially if swollen 1

Antibiotic Treatment

• First-line therapy: Amoxicillin-clavulanate (oral, outpatient) 1, 2
• Intravenous options (for severe infections):
  • β-lactam/β-lactamase combinations (ampicillin-sulbactam)
  • Piperacillin/tazobactam
  • Second-generation cephalosporins (cefoxitin)
  • Carbapenems (ertapenem, imipenem, meropenem) 1

Rationale for Aggressive Treatment

• Cat bites have high infection rates due to:
  • Deep puncture wounds from sharp teeth
  • Higher prevalence of Pasteurella multocida (75% of cat bites) 1, 3
  • Greater prevalence of anaerobes (65%) 1
  • Higher risk of osteomyelitis and septic arthritis 1
• Pasteurella multocida can cause rapidly developing cellulitis within 12-24 hours 3

Avoid These Antibiotics for Cat Bites

• First-generation cephalosporins (cephalexin)
• Penicillinase-resistant penicillins (dicloxacillin)
• Macrolides (erythromycin)
• Clindamycin
  • These have poor activity against P. multocida 1

Cat Scratch Infections

Immediate Management

• Wash scratch sites promptly and thoroughly 1
• Monitor for signs of infection

When to Use Antibiotics

• For immunocompetent patients: Only if signs of infection develop
• For immunocompromised patients (especially HIV-infected):
  • Consider prophylactic antibiotics due to risk of Bartonella infection 1
  • Azithromycin is effective for Bartonella henselae (cat-scratch disease) 4

Cat-Scratch Disease (Bartonella)

• Most common manifestation: regional lymphadenitis 4
• Atypical forms: Parinaud oculoglandular syndrome, neuroretinitis, persistent fever, hepatosplenic infection 4
• Most effective antibiotics: rifampin, ciprofloxacin, gentamicin, TMP-SMX, clarithromycin, and azithromycin 4

Special Considerations

Immunocompromised Patients

• HIV-infected persons are at higher risk for severe Bartonella infection 1
• Preventive measures:
  • Adopt cats >1 year old in good health 1
  • Implement flea control for cats 1
  • Avoid rough play with cats 1
  • Do not allow cats to lick open wounds 1

Hand Injuries

• Hand wounds from cats have the greatest risk of infection 2
• Prophylactic antibiotics significantly reduce infection rates in hand bites (NNT = 4) 5
• Monitor for pain disproportionate to injury near bones/joints (suggests periosteal penetration) 1

Potential Complications

• Septic arthritis
• Osteomyelitis
• Subcutaneous abscess
• Tendonitis
• Bacteremia (rare) 1
• In immunocompromised: bacillary angiomatosis, bacillary peliosis, relapsing bacteremia 4

Duration of Treatment

• Uncomplicated infections: 5-7 days
• Complicated infections:
  • Osteomyelitis: 4-6 weeks
  • Synovitis: 3-4 weeks 1

Remember that cat bites should always be taken seriously due to their high infection rate and potential for rapid progression, while scratches generally require close monitoring but less aggressive initial intervention unless the patient is immunocompromised.