Introduction

Capnocytophaga canimorsus is a commensal organism colonized in oral flora of dogs and cats and causes severe sepsis through bite wounds in immunocompromised patients.

Microbiology

Capnocytophaga species are slow growing, capnophilic ("carbon loving"), facultative anaerobes. They are long, thin, and generally fusiform gram-negative rods. C. canimorsus, C. cynodegmi, and C. stomatis are found in the oral cavity of dogs and cats, whereas all the other species are found in the human oral cavity.

Epidemiology

Risk Factors

dog and cat owners
immunocompromised individuals:
- asplenia
- cirrhosis
- alcoholism
- renal failure/dialysis

Clinical Presentation

Septic shock
- classical severe presentation is septic shock with fever, DIC, purpura, hypotension, AKI, AMS
- most associated with immunocompromised status
- In approximately half of cases, there is a history of dog bite or other contact with dog saliva and occasionally a history of cat scratch or contact with cat saliva
- delay between dog bite and clinical presentation ranges from 1 to 30 days, with an average of 5 to 6 days
Other presentations
- Sepsis
- FUO
- Cellulitis
- Meningitis
- Respiratory tract infection/pneumonia
- Periodontal disease

Diagnosis

Culture establishes the diagnosis. The organisms grow slowly and identification of the organism may take several days. C. canimorsus is more fastidious than other species and requires enriched agar; blood cultures turn positive after 1 to 14 days (mean 6 days) of incubation

Management

Acute Infection

IV antibiotics:
- beta-lactam beta-lactamase combination (pip-tazo) or a carbapenem
PO antibiotics:
- Amox-clav
Guide therapy based on susceptibility testing.
Capnocytophaga species can be resistant to penicillins, cephalosporins, carbapenems, aztreonam, and fluoroquinolones
There are no standard durations of therapy.

Prevention

Antibiotic prophylaxis with amox-clav for five days following a dog bite is appropriate for patients at highest risk (including patients with asplenia, patients with alcohol use disorder, patients receiving corticosteroids, or patients who are otherwise immunocompromised).