Antibiotic of Choice for Cat Bite
Amoxicillin-clavulanate 875/125 mg twice daily is the first-line antibiotic for cat bite infections, providing optimal coverage against Pasteurella multocida (present in 75% of cat bites) and the polymicrobial mix of aerobic and anaerobic bacteria typically found in these wounds. 1, 2, 3
Why Amoxicillin-Clavulanate is Preferred
Cat bites are particularly high-risk, with infection rates of 20-80% compared to only 3-18% for dog bites, and they more frequently cause deep tissue complications including osteomyelitis and septic arthritis 1, 4, 5
The microbiology is complex: Cat bite wounds contain an average of 5 different bacterial species, with P. multocida in 75% of cases, anaerobes in 65%, and staphylococci/streptococci in ~40% 1, 3
Amoxicillin-clavulanate provides comprehensive coverage against all major pathogens: P. multocida, staphylococci, streptococci, and anaerobes (Bacteroides, Fusobacterium, Porphyromonas, Prevotella) 1, 3, 4
High susceptibility rates persist: Studies show 100% susceptibility of P. multocida to amoxicillin-clavulanate, confirming it remains highly effective 4
Alternative Oral Options (When Amoxicillin-Clavulanate Cannot Be Used)
First-line alternative: Doxycycline 100 mg twice daily 2, 3
- Excellent activity against P. multocida
- Covers most pathogens except some streptococci may be resistant
- Particularly useful for penicillin-allergic patients
Second-line alternatives requiring additional anaerobic coverage:
- Fluoroquinolones (ciprofloxacin 500-750 mg twice daily, levofloxacin 750 mg daily, or moxifloxacin 400 mg daily) PLUS metronidazole or clindamycin for anaerobic coverage 1, 2
- Penicillin VK plus dicloxacillin (500 mg four times daily each) 1, 3
Critical Pitfalls to Avoid
Never use these as monotherapy for cat bites (they have poor activity against P. multocida): 1, 2, 3
- First-generation cephalosporins (cephalexin)
- Penicillinase-resistant penicillins alone (dicloxacillin)
- Macrolides (erythromycin, azithromycin)
- Clindamycin alone
- Trimethoprim-sulfamethoxazole
Intravenous Options for Severe Infections
When hospitalization is required (systemic infection, rapidly progressing infection despite oral antibiotics, deep tissue involvement, immunocompromised host): 2, 3
- 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 (cefoxitin 1 g every 6-8 hours) 1, 2
- Carbapenems (ertapenem, imipenem, meropenem) 1, 3
Duration and Follow-Up
- Standard duration: 7-14 days for uncomplicated infections 3
- Extended duration: 4 weeks for deep tissue infections or abscesses 6
- Mandatory 24-hour follow-up either by phone or office visit to assess response 3
- Consider hospitalization if infection progresses despite appropriate oral therapy 2, 3
Additional Management Considerations
- Wound care is equally important as antibiotics: Thorough irrigation with sterile saline, debridement of superficial debris, avoid closing infected wounds, and elevate the injured extremity 1, 3
- Update tetanus prophylaxis if vaccination status is outdated or unknown 3, 5
- Order both aerobic and anaerobic cultures for infected wounds to identify resistant organisms like Bacteroides pyogenes 6