Case report: Meningitis of a 66-year-old dog owner caused by Capnocytophaga canimorsus.

Capnocytophaga canimorsus is a fastidious Gram-negative rod transmitted from dog saliva and typically associated with immunocompromised hosts. We report meningitis in a 66-year-old immunocompetent dog owner with prior cerebral amyloid angiopathy who presented with acute global aphasia, fever and inflammatory cerebrospinal fluid (CSF) consistent with bacterial meningitis, but without meningism or history of any dog bite. Fusiform Gram-negative rods in CSF prompted extended culture in thioglycolate broth, enabling growth and subsequent species identification by MALDI-TOF MS as C. canimorsus within five days. Antimicrobial susceptibility testing was performed according to EUCAST guidance for situations without species-specific breakpoints and supported continuation of ceftriaxone-based therapy for a total of 15 days, resulting in complete clinical remission and normalization of CSF parameters. This case underlines that C. canimorsus meningitis can occur in apparently immunocompetent elderly patients, illustrates the diagnostic value of targeted culture strategies, and emphasizes the feasibility of EUCAST-guided susceptibility testing for this rare pathogen.