Capnocytophaga canimorsus from Dog Saliva Exposure Causing Severe Sepsis in a Healthy Adult: A Case Report

Abstract

BACKGROUND Capnocytophaga canimorsus is a gram-negative bacterium commonly found in the saliva of dogs and cats. It has the ability to evade the human immune system and cause life-threatening infections, particularly in immunocompromised individuals. C. canimorsus infection was first described in 1976, and additional cases have since been reported, with complications varying from mild to severe. This case report highlights the occurrence of a severe C. canimorsus infection in an immunocompetent patient, which rapidly progressed to septic shock and multiorgan failure. CASE REPORT We present the case of a 63-year-old man with no significant past medical history who presented with weakness, fatigue, and confusion. Further investigation revealed a wound on his lower right extremity, which had been licked by his dog. The causative pathogen was identified as C. canimorsus through blood culture and mass spectrometry. The patient experienced septic shock with multiorgan failure, including acute renal failure, liver failure, and coagulopathy. Prompt initiation of empirical broad-spectrum antibiotics prior to identification of the source of infection proved to be beneficial, resulting in clinical and symptomatic improvement for the patient. CONCLUSIONS This case emphasizes the severe complications that can arise from C. canimorsus infection in immunocompetent individuals, underscoring the importance of early recognition and treatment in cases of sepsis, particularly in those with potential dog saliva exposure.

Figure 1.

Contrasted computed tomography of the chest, abdomen, and pelvis, which revealed mild bilateral atelectasis, persistent bilateral nephrograms concerning for acute tubular necrosis without hydronephrosis or perinephric fluid collection (green arrows), and mild hepatomegaly (red arrow).

Figure 2.

Capnocytophaga canimorsus Gram stain image, showing gram-negative fusiform bacilli. Sample culture image obtained from the Microbiology Department at Northeast Georgia Medical Center.

Figure 3.

Infected wound on the patient’s right shin, characterized by necrosis. The wound features a central black eschar, surrounded by a violaceous (purple) and erythematous (red) rim. The estimated size of the necrotic center is 0.5 to 1 cm, with surrounding erythema and induration extending 1 to 2 cm beyond it.