Intravenous Antibiotic Therapy for Worsening Cat Bite Infections
For worsening cat bite infections requiring intravenous therapy, ampicillin-sulbactam, piperacillin-tazobactam, or a carbapenem should be administered as first-line treatment to effectively cover Pasteurella multocida and anaerobic pathogens. 1
Microbiology and Pathogen Considerations
Cat bites have a high infection rate (20-80%) compared to dog bites (3-18%), primarily due to:
- Pasteurella multocida (present in approximately 90% of cat oral flora) 2, 3
- Anaerobic bacteria including Bacteroides species 4, 5
- Staphylococci and streptococci 1, 6
IV Antibiotic Selection Algorithm
First-line IV options:
- Ampicillin-sulbactam
- Piperacillin-tazobactam
- Carbapenems (imipenem, meropenem, ertapenem)
These options provide excellent coverage against both Pasteurella and anaerobic pathogens that commonly cause worsening cat bite infections 1.
Alternative IV options (for penicillin allergies):
- Fluoroquinolone (ciprofloxacin or levofloxacin) PLUS metronidazole
- Second/third-generation cephalosporins with anaerobic coverage
- Doxycycline (contraindicated in pregnancy) 1
Clinical Management Considerations
Indications for IV therapy and hospitalization:
- Severe infections with systemic symptoms
- Deep infections involving tendons or joints
- Hand infections (particularly high risk)
- Immunocompromised patients with moderate to severe infections
- Failed oral antibiotic therapy 1
Surgical intervention is necessary when:
- Abscess formation is present
- Deep structures are involved
- Necrotic tissue is evident
- Foreign body is suspected 1
Treatment Duration and Monitoring
- Initial IV therapy should be continued until clinical improvement is observed
- Transition to oral amoxicillin-clavulanate (875/125 mg twice daily) can be considered once improvement occurs 1, 4
- Total treatment duration typically ranges from 5-7 days for uncomplicated infections, but may be extended to 2-4 weeks for complicated infections involving deep tissues 1, 4
- Monitor for response within 24-48 hours of initiating treatment 1
Special Considerations and Pitfalls
- Cat bites to the hand warrant special attention due to higher risk of treatment failure and may require more aggressive treatment 1
- Both aerobic and anaerobic cultures should always be obtained to guide therapy 4
- Antibiotic resistance in Bacteroides species is a growing concern, requiring careful selection of antibiotics with anaerobic coverage 4
- Necrotizing fasciitis is a rare but potentially fatal complication of cat bites that requires immediate surgical debridement in addition to IV antibiotics 5
- High-risk patients (immunocompromised, elderly, those with cirrhosis or asplenia) require broader spectrum antibiotics and closer monitoring 1
Wound Management
- Thorough debridement of necrotic tissue
- Irrigation with sterile saline or dilute povidone-iodine solution
- Drainage of purulent collections
- Removal of foreign bodies if present 1