Capnocytophaga canimorsus Bacteremia Without Animal Bite: A Rare but Severe Infection to Consider in Older Adults.

BACKGROUND Capnocytophaga canimorsus is a gram-negative bacillus found in the oral cavity of dogs and cats. Human infection is uncommon but can cause severe sepsis. Although classically associated with asplenia, alcohol use disorder, or immunosuppression, a substantial proportion of cases occur in patients without identifiable risk factors. Diagnosis may be delayed due to the fastidious nature of the organism and the impact of prior antibiotic exposure on culture yield. CASE REPORT A 75-year-old woman presented with fever and right upper-quadrant abdominal pain 6 weeks after right total hip arthroplasty. She had no history of animal bite but reported close contact with dogs. Initial investigations did not identify a source of infection, and empirical ceftriaxone was initiated. Blood cultures became positive after extended incubation (Day 10), with identification of C. canimorsus by MALDI-TOF mass spectrometry. Imaging studies were inconclusive for prosthetic joint infection. The patient was treated with high-dose amoxicillin for 14 days, with favorable clinical and biological outcomes. CONCLUSIONS C. canimorsus infection should be considered in patients presenting with sepsis or persistent fever and a history of dog or cat exposure, even in the absence of a bite. Close collaboration with microbiology laboratories may be required to ensure appropriate culture conditions. Clinicians should also be aware of the potential for diagnostic uncertainty in patients with recent prosthetic implants.