What are the criteria for prescribing antibiotics, such as amoxicillin-clavulanate (Augmentin) or doxycycline, to a patient with a cat scratch and/or bite, considering factors like wound depth, signs of infection, and medical history, including immunosuppression?

Antibiotic Criteria for Cat Scratches and Bites

Prescribe prophylactic antibiotics with amoxicillin-clavulanate for deep wounds, wounds on hands/feet/face/near joints, and all immunocompromised patients, while superficial scratches in healthy individuals require only thorough wound cleaning and observation. 1

Risk Stratification for Antibiotic Initiation

High-Risk Wounds Requiring Prophylactic Antibiotics 1

• Deep wounds penetrating through the skin (present in 92% of infected cases) 2
• Hand wounds - carry the greatest infection risk due to proximity to tendons, joints, and bone 1, 3
• Wounds on feet, face, or near joints 1
• Cat bites specifically - have 30-50% infection rate compared to 10-20% for scratches 1
• Immunocompromised patients - require aggressive treatment with lower threshold for antibiotics due to risk of disseminated disease including bacillary angiomatosis 1

Low-Risk Wounds (Observation Without Prophylaxis) 1

• Superficial scratches not penetrating dermis in immunocompetent patients
• Wounds on trunk or proximal extremities (away from hands/feet)
• Scratches from known healthy indoor cats in immunocompetent hosts

Critical pitfall: Cat bite wounds may appear trivial but have high infection potential - do not be falsely reassured by small puncture size 3. The rapid onset of cellulitis within 12-24 hours after cat wounds strongly suggests Pasteurella multocida infection 2.

First-Line Antibiotic Selection

Preferred Regimen 1

• Amoxicillin-clavulanate 875/125 mg twice daily for adults
• Provides optimal coverage against Pasteurella multocida (isolated in >50% of cat bites) and other common pathogens 1, 3

Penicillin-Allergic Patients 1

• Doxycycline 100 mg twice daily - excellent Pasteurella activity
• Fluoroquinolones: Ciprofloxacin 500-750 mg twice daily or levofloxacin 750 mg daily
• TMP-SMX plus metronidazole for combined aerobic/anaerobic coverage

Important caveat: Clindamycin should NOT be used as monotherapy because it lacks Pasteurella coverage despite good activity against staphylococci and anaerobes 1. First-generation cephalosporins also have no activity and should be avoided 4.

Special Population Considerations

Diabetic Patients 1

• Require more aggressive treatment due to impaired immune response and delayed wound healing
• Treat for 1-2 weeks for mild infections, extending to 3-4 weeks if extensive or slow resolution
• Provide optimal wound care including debridement and off-loading
• Early surgical consultation for deep abscess, extensive necrosis, or necrotizing fasciitis

Immunocompromised Patients 1, 4

• Lower threshold for antibiotic initiation
• Vigilance for atypical presentations including bacillary angiomatosis (especially CD4+ <100 cells/µL)
• Consider extended therapy duration
• HIV patients with CD4+ <100 cells/µL may not develop antibodies despite active infection 4

Pregnant Women 4

• Erythromycin is the only safe option - avoid tetracyclines (doxycycline) completely
• Fluoroquinolones should not be used
• Prompt wound washing is the most critical intervention

Essential Wound Management 1

• Thorough cleansing with sterile normal saline to remove superficial debris
• Deeper debridement usually unnecessary unless significant devitalized tissue present
• Evaluate tetanus immunization status and update if needed
• Assess rabies risk for scratches from unknown or feral cats
• Elevate injured body part if swollen to accelerate healing

Cat Scratch Disease vs. Wound Infection

This is a critical distinction that changes management:

Acute Wound Infection (12-72 hours post-injury) 1, 2

• Rapid cellulitis, lymphangitis, serosanguineous/purulent drainage
• Caused by Pasteurella multocida
• Treatment: Amoxicillin-clavulanate as above

Cat Scratch Disease (3-30 days post-exposure) 5, 4

• Papule/pustule followed by regional lymphadenopathy ~3 weeks later
• Caused by Bartonella henselae
• Treatment: Azithromycin 500 mg day 1, then 250 mg for 4 days (>45 kg) or weight-based dosing for children 1, 4
• Most immunocompetent cases are self-limited and don't require antibiotics 6, 7
• Treat if immunocompromised, extranodal disease, or severe symptoms 4

Follow-Up Instructions 1

• Return immediately if signs of infection develop: increasing pain, redness, swelling, purulent drainage, fever
• Monitor for complications including septic arthritis, osteomyelitis, or tendonitis (especially hand wounds)
• Diabetic patients require early and careful follow-up to ensure treatment effectiveness

Prevention Counseling 4

• Keep cats indoors and prevent hunting
• Maintain comprehensive flea control (fleas transmit Bartonella between cats)
• Avoid rough play and activities provoking scratches
• Wash hands after handling cats
• Never allow cats to lick open wounds