When Man’s Best Friend Turns Fatal

An immunocompetent 62-year-old male with a 1-day history of dyspnea, fever, abdominal discoloration, and bilateral arm wounds due to dog bites was transferred to our hospital in septic shock. After multiple bacterial cultures without growth, plasma microbial cell-free DNA (mcfDNA) sequencing confirmed Capnocytophaga canimorsus infection, despite 13 days of appropriate antimicrobial treatment. The hospital course was complicated by purpura fulminans, multiorgan failure, progressive tissue necrosis, and superinfection, and the patient died from cardiac arrest 1 month later. This case underscores the challenges of diagnosing and treating C. canimorsus sepsis and highlights the utility of mcfDNA testing for diagnosing slow-growing, fastidious pathogens.