Infective endocarditis (IE) is an uncommon but life‐threatening disease, most frequently caused by Staphylococcus aureus , streptococci, and enterococci. Vagococcus fluvialis is a Gram‐stain positive coccus, phenotypically close to enterococci, and rarely identified in human infections due to diagnostic challenges. We present a case report of a patient with a prosthetic valve endocarditis caused by V . fluvialis, along with details of the treatment initiated in a 63‐year‐old man with a history of mitral valve bioprosthesis for prior IE. He presented with fever, confusion, asthenia, and myalgia. Echocardiography identified a large vegetation on the mitral prosthesis. Blood cultures grew V. fluvialis , confirmed by MALDI‐TOF mass spectrometry and 16S RNA sequencing. Antibiotic therapy with intravenous amoxicillin led to rapid clinical and microbiological improvement. However, despite this favorable initial clinical response, follow‐up echocardiography demonstrated progression of the vegetation, ultimately necessitating a redo mitral valve replacement on Day 20. Intraoperative findings confirmed extensive vegetation without paravalvular complications. Although the prosthesis cultures were negative, sequencing identified V. fluvialis again. Postoperative recovery was uneventful, and the patient was discharged in good condition. V. fluvialis is increasingly recognized in human infections but remains difficult to distinguish from enterococci using conventional methods. Accurate diagnosis requires advanced tools such as 16S RNA sequencing. Unlike previous cases, this prosthetic valve IE progressed more slowly, characterized by persistent vegetation rather than acute valve destruction. Successful management was achieved through amoxicillin therapy combined with surgical intervention. This case highlights V. fluvialis as a rare but emerging cause of IE, emphasizes the need for precise microbiological identification, and suggests that amoxicillin monotherapy may contribute to initial clinical stabilization. Further reports are required to specify V. fluvialis ‐related IE prognosis and to establish the most effective treatment.
Guillou et al. (Thu,) studied this question.