Severe Capnocytophaga Canimorsus Purpura Fulminans After a Cat Bite in an Asplenic Patient: Diagnostic and Therapeutic Challenges

TL;DR

An asplenic man developed a severe Capnocytophaga canimorsus infection after a cat bite, requiring intensive care and highlighting the need for early diagnosis and treatment.

Contribution

This case highlights the diagnostic challenges and immune evasion of C. canimorsus in at-risk patients following animal bites.

Findings

C. canimorsus caused severe septic shock and purpura fulminans in an asplenic man after a cat bite.

Microbial cell-free DNA testing was crucial for identifying the pathogen after negative cultures.

Early empirical antibiotic coverage improved outcomes in this high-risk infection.

Abstract

Capnocytophaga canimorsus, a gram-negative bacterium often found as part of the oral flora of dogs, can cause life-threatening infections in immunocompromised patients, usually secondary to a dog bite or scratch. This case report describes a life-threatening Capnocytophaga infection causing bacteremia and severe septic shock with multiple organ dysfunction in an asplenic man who was bitten by a cat.

We present a case of a 53-year-old asplenic man who developed severe septic shock, disseminated intravascular coagulation (DIC), and purpura fulminans following a minor cat bite. Despite prompt treatment with broad-spectrum antibiotics, his condition worsened to multiorgan failure. He required hemodialysis, mechanical ventilation, and management of acute vascular thrombosis, which led to prolonged intensive care. Diagnosis of the causative pathogen was initially delayed due to negative cultures, but microbial cell-free DNA testing ultimately identified C. canimorsus. Targeted therapy with meropenem led to eventual stabilization and improvement. This case highlights the pathogen’s immune evasion mechanisms and the importance of early empirical antibiotic coverage in at-risk patients. It also highlights the importance of thorough history-taking when suspecting unusual disease presentation, as this can lead to a timely diagnosis of a catastrophic illness.

Given the organism's slow growth in cultures and emerging resistance patterns, clinicians should be aware of the prevalence of C. canimorsus following dog or cat bites in immunocompromised patients to improve outcomes in severe infections.

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