# A “fishy” situation, rare pathogen and presentation in prosthetic valve infective endocarditis

## TL;DR

This case report describes a rare instance of Lactococcus garviae causing prosthetic valve infective endocarditis and highlights the importance of early recognition and advanced imaging for diagnosis.

## Contribution

The report presents the 27th global and 7th U.S. case of L. garviae prosthetic valve infective endocarditis and emphasizes the diagnostic utility of 18F-FDG PET/CT.

## Key findings

- 18F-FDG PET/CT aids in diagnosing prosthetic valve endocarditis when TEE and TTE are negative.
- L. garviae infections are rare but associated with high mortality similar to streptococcus.
- Early recognition of L. garviae infection improves patient outcomes in infective endocarditis.

## Abstract

Lactococcus garviae (L. garviae) is a gram-positive coccus belonging to the Streptococcaceae family. While primarily a pathogen in fish farms causing hemorrhagic sepsis, it can act as a rare opportunistic pathogen in humans. A 2021 case report by Bravo et al. documented less than 30 cases of infective endocarditis caused by L. garviae worldwide at that time [1]. This case report describes the 27th documented case globally and 7th documented case in the USA of L. garviae causing infective endocarditis of a prosthetic valve [1].

L. garviae is found in unpasteurized dairy products, raw fish, and meat (pork, beef, and poultry), but the route of human transmission remains unclear [3]. It seems to have a predilection for individuals with prosthetic valves, immunocompromised states, prior gastrointestinal surgery, gastrointestinal disorders (colon polyps and diverticulosis), and the use of acid-reducing medications [1-3]. Infective endocarditis is the most common systemic disease caused by L. garviae [1-4].

This report details the case of a 75-year-old male, with multiple comorbidities and risk factors for L. garviae infection who was admitted for “symptomatic anemia”. High clinical suspicion, coupled with an inadequate hemoglobin response to transfusion, a normal anemia workup, and blood cultures positive for L. garviae, promoted a transesophageal echocardiogram (TEE). However, the results were negative. Consequently, an 18F-fluorodeoxyglucose positron emission tomography/computed tomography scan (18FDG PET/CT) was performed. The scan revealed increased uptake in the aortic valve replacement consistent with prosthetic valve endocarditis in the setting of Lactococcus garviae bacteremia.

•Mortality caused by L. garviae is proportionate to streptococcus.•Lactococcus garviae is a rare human pathogen.•Early recognition improves overall morbidity/mortality in infective endocarditis.•18F-FDG PET/CT(A) aids diagnosis with prosthetic valves and negative TTE/TEE.•Ultrasound and modified Duke Criterion are limited with prosthetic valves.

Mortality caused by L. garviae is proportionate to streptococcus.

Lactococcus garviae is a rare human pathogen.

Early recognition improves overall morbidity/mortality in infective endocarditis.

18F-FDG PET/CT(A) aids diagnosis with prosthetic valves and negative TTE/TEE.

Ultrasound and modified Duke Criterion are limited with prosthetic valves.