Infection Caused by Dog and Cat Bites
Pasteurella species are the primary cause of infection from dog and cat bites. 1, 2, 3
Microbiology of Animal Bite Infections
Dog Bites
- Pasteurella canis is the most common pathogen isolated from dog bite infections 1
- Approximately 20-30% of dog bite wounds contain Pasteurella species 4
- Other common organisms include:
- Staphylococcus species
- Streptococcus species
- Capnocytophaga canimorsus
- Various anaerobes
Cat Bites
- Pasteurella multocida is found in over 50% of infected cat bite wounds 4, 5
- Cat bites have a significantly higher infection rate (20-80%) compared to dog bites (3-18%) 2
- Studies have shown approximately 90% carriage rate of P. multocida in the oral cavity of domestic cats 2
Clinical Presentation and Complications
Pasteurella infections typically present with:
- Rapid onset of cellulitis at the bite site
- Development within 12-24 hours after injury
- Serosanguineous or purulent drainage
- Lymphangitis 3
Potential complications include:
- Deep tissue infection
- Osteomyelitis
- Septic arthritis (particularly with bites near joints)
- Systemic infections in immunocompromised patients 3
Other Potential Pathogens
While Pasteurella species are the predominant cause, other pathogens may be involved:
- Staphylococcus aureus (including MRSA in some cases)
- Streptococcus species
- Capnocytophaga canimorsus (can cause severe sepsis)
- Moraxella species
- Anaerobic bacteria (present in approximately one-third of bite wounds) 1, 6, 5
Treatment Considerations
- Penicillin and its derivatives remain the treatment of choice for Pasteurella infections 2, 3
- Amoxicillin-clavulanate is recommended for empiric treatment of dog and cat bite wounds to cover both Pasteurella and other potential pathogens 4
- High antibiotic susceptibility has been observed for benzylpenicillin (100%), amoxicillin-clavulanate (100%), cefazolin (98.37%), and azithromycin (94.02%) against P. multocida 2
Common Pitfalls in Management
- Underestimating the severity of cat bites, which have higher infection rates than dog bites
- Failing to consider Pasteurella as the primary pathogen, which requires appropriate antibiotic coverage
- Delaying treatment, as Pasteurella infections can progress rapidly
- Inadequate wound cleansing and debridement, which are essential components of management
- Not considering tetanus prophylaxis when indicated
In conclusion, while animal bites can introduce various pathogens including Staphylococcus aureus, Mycobacterium, Actinomyces, and Candida, Pasteurella species are clearly the predominant causative organisms in infections resulting from dog and cat bites.