From the Guidelines
The recommended treatment for infections caused by dog scratch pathogens, including Capnocytophaga canimorsus, is amoxicillin-clavulanate (875/125 mg twice daily for adults) for 5-7 days as the first-line treatment. This recommendation is based on the most recent and highest quality study available, which prioritizes the treatment of such infections to prevent severe outcomes, particularly in vulnerable individuals such as those who are immunocompromised, asplenic, or have liver disease 1.
Key Considerations for Treatment
- For mild infections, amoxicillin-clavulanate is the preferred choice due to its broad-spectrum activity against the common pathogens involved in dog scratch infections, including Capnocytophaga canimorsus, Pasteurella multocida, and various anaerobes.
- In cases of penicillin allergy or more severe infections, alternative antibiotics such as doxycycline, trimethoprim-sulfamethoxazole, or fluoroquinolones like ciprofloxacin can be considered, taking into account the specific resistance patterns and the patient's condition 1.
- Severe Capnocytophaga infections may necessitate intravenous antibiotics, including beta-lactam/beta-lactamase inhibitors, third-generation cephalosporins, or carbapenems, for a duration of 10-14 days, especially in immunocompromised patients.
- Prompt and thorough wound cleaning with soap and water immediately after the injury is crucial for preventing infection, and patients should seek medical attention if they develop signs of infection, such as fever, increasing pain, redness, swelling, or pus from the wound.
Prevention and Special Considerations
- Patients who are at higher risk of severe infection, including those who are immunocompromised, asplenic, or have liver disease, should be particularly vigilant and seek medical attention promptly if they experience any symptoms of infection after a dog scratch.
- The bacteriology of dog scratch wounds can be complex, involving a variety of aerobic and anaerobic pathogens, which underscores the importance of empirical antibiotic therapy that covers a broad spectrum of potential pathogens until culture results are available, if cultures are performed 1.
Given the potential for severe infections, including sepsis, particularly in vulnerable individuals, early recognition and treatment of dog scratch infections are critical to preventing morbidity, mortality, and reducing the impact on quality of life.
From the Research
Pathogens Related to Dog Scratches
- Capnocytophaga canimorsus is a gram-negative, capnophilic rod that constitutes normal bacterial flora of the oral cavity of dogs and cats, and can cause infections in humans, including sepsis, endocarditis, and meningitis 2, 3, 4.
- Infections can occur after dog bites, scratches, licks, or simply exposure to dogs or cats, and can be severe, especially in immunocompromised individuals, such as those with asplenia, cirrhosis, or alcohol abuse 2, 4, 5, 6.
Recommended Treatment
- Amoxicillin with clavulanic acid is considered the drug of choice for prophylaxis of C. canimorsus infections 2.
- Early wound cleansing, initial use of penicillins in combination with beta-lactamase inhibitors, and surgical removal of an infectious focus may be protective factors against fatal outcome 5.
- Prompt initiation of empirical broad-spectrum antibiotics prior to identification of the source of infection can be beneficial in cases of sepsis, particularly in those with potential dog saliva exposure 3.
Risk Factors and Complications
- Male gender, older age, and transmission by bite are risk factors for sepsis and fatal outcome 5.
- Incubation time ≤3 days is a risk factor for sepsis on admission 5.
- Sepsis and septic shock are risk factors for fatal outcome, whereas early wound cleansing, initial penicillin therapy with beta-lactamase inhibitors, and surgical removal of infectious focus are protective factors 5.
- Neurologic involvement, including meningitis and cerebritis, can occur in immunocompetent patients with C. canimorsus infection 6.