Atypical Gastrointestinal Presentation and Overcoming Diagnostic and Therapeutic Challenges in Fulminant Capnocytophaga canimorsus Sepsis

<p><strong>Background:</strong></p> <p> </p> <p><em>Capnocytophaga canimorsus </em>is a fastidious, zoonotic Gram-negative bacillus that can cause rapidly fatal septicaemia. Delays in microbiological diagnosis due to slow growth are common, reducing survival chances. This case uniquely highlights both an atypical gastrointestinal presentation and the resolution of a diagnostic impasse through extended CO₂ incubation triggered by astute clinical suspicion.</p> <p><strong>Case Presentation:</strong></p> <p>A 57-year-old male, recently tapered off corticosteroids for inflammatory arthritis, presented with diarrhoea, vomiting, and hypotensive collapse. He rapidly developed disseminated intravascular coagulation and multi-organ failure. Empirical piperacillin–tazobactam and gentamicin failed; cultures flagged positive at 72 hours with no initial growth. Only after clinicians alerted the laboratory, extended incubation under CO₂ enabled growth of <em>C. canimorsus</em> by day seven, confirmed via MALDI-TOF. Switching to meropenem led to recovery, although amputations of the necrotic tissues, including both toes and digits from his right hand were necessary due disseminated intravascular coagulation.</p> <p> </p> <p><strong>Conclusion:</strong></p> <p>This case demonstrates that <em>C. canimorsus</em> infection may initially mimic gastroenteritis and progress rapidly to fulminant sepsis. Early clinical suspicion, timely communication with microbiology for adapted incubation protocols, and prompt escalation to effective antimicrobial therapy are critical for survival.</p>