What is the recommended antibiotic regimen for a cat bite?

Recommended Antibiotic Regimen for Cat Bites

Amoxicillin-clavulanate 875/125 mg orally twice daily is the first-line antibiotic for cat bite infections, providing optimal coverage against the polymicrobial flora including Pasteurella multocida, staphylococci, streptococci, and anaerobes. 1, 2

Risk Stratification and When to Treat

Cat bites carry a 30-50% infection risk, significantly higher than dog bites (5-25%), making them particularly dangerous. 3

Antibiotic prophylaxis should be initiated for:

• Fresh, deep wounds 3
• Bites to high-risk locations: hands, feet, areas near joints, face, genitals 3
• Hand wounds specifically (highest infection risk with potential for septic arthritis, osteomyelitis, and tendonitis) 1
• Persons at elevated risk: immunocompromised patients, diabetes, liver disease, asplenia, artificial heart valves, or on immunosuppressive therapy 3, 1
• Any bite presenting within 24 hours 3

Do NOT give antibiotics if:

• Patient presents ≥24 hours after the bite AND there are no clinical signs of infection 3

Microbiology Driving Treatment Choice

Cat bites contain an average of 5 different bacterial species per wound. 1, 2 The key pathogens requiring coverage are:

• Pasteurella multocida (present in ~75% of cat bites) - the predominant pathogen 1, 2, 4
• Staphylococci and streptococci (~40% of bites) 1, 2
• Anaerobes including Bacteroides, Fusobacterium, Porphyromonas, and peptostreptococci (65% of bites) 1, 2
• Capnocytophaga canimorsus (can cause disseminated infection in asplenic/immunocompromised patients) 3, 1

Oral Antibiotic Options

First-line therapy:

• Amoxicillin-clavulanate 875/125 mg twice daily - provides complete coverage of all relevant pathogens 1, 2, 5, 6, 7

Alternative oral regimens (if penicillin allergy or intolerance):

• Doxycycline 100 mg twice daily (excellent P. multocida coverage, though some streptococci may be resistant) 1, 2
• Penicillin VK plus dicloxacillin (500 mg four times daily for each) 1, 2

Duration: 3-5 days for uncomplicated prophylaxis/treatment 3

Antibiotics to AVOID

These regimens have poor or absent activity against P. multocida and will fail:

• First-generation cephalosporins (e.g., cephalexin) 1, 2
• Penicillinase-resistant penicillins alone (e.g., dicloxacillin monotherapy) 1, 2
• Clindamycin monotherapy (misses P. multocida) 1, 2
• Macrolides (e.g., erythromycin) 2

This is a critical pitfall - these commonly prescribed antibiotics for skin infections are inadequate for cat bites due to the unique microbiology. 1, 2

Intravenous Options for Severe Infections

Indications for hospitalization and IV therapy:

• Systemic signs of infection 3
• Rapidly progressing infection 1
• Deep tissue involvement 1
• Immunocompromised hosts 3
• Failure of outpatient therapy 2

IV antibiotic choices:

• Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1, 2
• Piperacillin-tazobactam 3.37 g every 6-8 hours 1, 2
• Second-generation cephalosporins (e.g., cefoxitin 1 g every 6-8 hours) 1, 2
• Carbapenems (ertapenem, imipenem, meropenem) 1, 2

Wound Management Essentials

Immediate wound care:

• Thoroughly cleanse with sterile normal saline (NOT high-pressure irrigation, which spreads bacteria deeper) 3, 1, 2
• Remove superficial debris and necrotic tissue 3, 1, 2
• Do NOT close infected wounds 1, 2
• Elevate the injured body part to accelerate healing 1, 2
• Explore carefully for deep tissue involvement: tendon penetration, bone involvement, or joint space violation 1

Additional considerations:

• Update tetanus prophylaxis if status is outdated or unknown 1, 2
• Consider rabies post-exposure prophylaxis based on animal observation status 1

Follow-Up Protocol

• All outpatients must be followed up within 24 hours (phone or office visit) 1, 2
• If infection progresses despite appropriate therapy, hospitalize immediately 1, 2

Extended Treatment for Complications

If complications develop, treatment duration must be extended:

• Osteomyelitis: 4-6 weeks of antibiotic therapy 2
• Septic arthritis/synovitis: 3-4 weeks of antibiotic therapy 2
• Tendonitis: prolonged therapy required 1, 2

Special Populations

Immunocompromised patients require aggressive management:

• Patients with diabetes, liver disease, asplenia, or on immunosuppressive therapy have impaired immune response 1
• Risk of disseminated infection from Capnocytophaga canimorsus causing septic shock, meningitis, and endocarditis 1
• Lower threshold for hospitalization and IV therapy 1

Common Pitfalls to Avoid

• Relying solely on topical antibiotics without systemic coverage 1
• Delaying treatment (can lead to septic arthritis, osteomyelitis, or tendonitis) 1
• Using antibiotics with poor P. multocida coverage 1, 2
• High-pressure wound irrigation (spreads bacteria deeper) 3
• Closing infected wounds 1, 2