Infective endocarditis due to <i>Lactococcus garvieae</i> , an unusual emerging pathogen

Background: Lactococcus garvieae is an emerging, fish-associated zoonotic pathogen that rarely causes human infection but is increasingly linked to serious conditions like infective endocarditis (IE). Lactococcus spp are phylogenetically and phenotypically related to Streptococcus and Enterococcus spp as all three genera are Gram-positive, catalase-negative, lactic acid–producing cocci that belong to the family Streptococcaceae. Due to these shared characteristics, L. garvieae is frequently misidentified by traditional biochemical methods, necessitating advanced techniques for definitive diagnosis. Case Presentation: We present the case of a 61-year-old male patient with native valve IE secondary to L. garvieae. This represents only the second reported Canadian case of L. garvieae IE and is unique in that the infection involved the native aortic valve despite the presence of a mechanical valve. Furthermore, the case is characterized by an occult source of inoculation as the patient lacked the typical risk factors of raw seafood consumption or occupational exposure to aquaculture. This clinical presentation underscores the importance of considering L. garvieae in the differential diagnosis of IE, even in the absence of traditional zoonotic links.