A 42-year-old woman with septic shock: an unexpected source

Dog bites are the most common animal bite injuries occurring in the United States. Estimated infection rates range between 15% and 20%. Polymicrobial infections are most common. Capnocytophaga canimorsus (C. canimorsus) is a Gram-negative rod strongly associated with dog bites, and is known to cause life-threatening infection in humans.

1) Outline epidemiology of dog bites in the United States; 2) Identify host factors associated with infection, and common pathogens; 3) Discuss microbiology of C. canimorsus; 4) Discuss common clinical manifestations of C. canimorsus infection; 5) Outline treatment options.

A 42-year-old woman with a remote history of Hodgkin's lymphoma (treated with irradiation) and thyroid carcinoma, both of which were in remission, presented to the Emergency Department with fever, abdominal pain, and diarrhea. She was found to be in septic shock. She was aggressively resuscitated and administered broad-spectrum antibiotics. Blood cultures grew C. canimorsus in 2/4 bottles. The patient recalled being bitten by the family dog 48 h before her initial presentation. She made an uneventful recovery. She was felt to be "functionally hyposplenic" due to her prior irradiation.

C. canimorsus is a rare pathogen strongly associated with dog bites. By eliciting a history of animal bite, clinicians may be able to alert the laboratory of suspected C. canimorsus infection. Prolonged laboratory incubation times may be necessary as the organism is fastidious. Predisposing conditions include, among others, prior splenectomy and alcoholism. The mortality rate from C. canimorsus sepsis is high, so treatment should be promptly initiated.