Dog and Cat Bite–Related Skin and Soft Tissue Infection Antimicrobial Spectrum
Amoxicillin-clavulanate is recommended because it is active against the aerobic and anaerobic organisms commonly involved in bite-wound infections. [1] Cephalexin provides limited activity for the anaerobic components of bite-wound polymicrobial flora, so organisms requiring anaerobic coverage are not reliably covered. [1], [2]
Organisms Covered by Amoxicillin-Clavulanate but Not Reliably Covered by Cephalexin
The main organism group uniquely addressed by amoxicillin-clavulanate in bite-wound SSTIs is anaerobic bacteria. [1], [2]
- Bacteroides spp. (anaerobic gram-negative bacilli) [2]
- Fusobacterium nucleatum (anaerobic gram-negative bacilli) [2]
Treatment Implication for Empiric Therapy
Empiric therapy for infected animal bite–related wounds should use an agent active against both aerobic and anaerobic bacteria, such as amoxicillin-clavulanate. [1]
Key Guideline Basis
The IDSA guideline states that amoxicillin-clavulanate is appropriate oral therapy that covers the most likely aerobes and anaerobes found in bite wounds. [1] The NICE guidance lists anaerobes such as Bacteroides and Fusobacterium nucleatum among organisms associated with infections from dog and cat bites. [2]
Practical Boundaries of the Coverage Comparison
Cephalexin is not an anaerobe-active regimen for bite-wound SSTI pathogens, so anaerobic organisms listed above are the organisms that amoxicillin-clavulanate covers in a way cephalexin does not. [1], [2]