Mitral Valve Endocarditis by Micrococcus luteus

Case summary: An 88-year-old woman with atrial fibrillation presented with worsening dyspnea after recent pneumonia and bronchitis. Echocardiography showed mobile vegetation on the mitral and aortic valves, severe mitral regurgitation, and mitral leaflet perforation. Blood cultures were negative, but the valve tissue grew Micrococcus luteus. She received empiric antibiotics and underwent successful replacement of the mitral valve with bioprosthesis and aortic valve shaving via endoscopic right minithoracotomy. Recovery was uneventful, and a 6-week antibiotic course was completed. Discussion: This case illustrates Mluteus as an emerging cause of infective endocarditis in susceptible patients and underscores the importance of early recognition and intervention to optimize outcomes. Take-home messages: Rare microorganisms such as Mluteus can become opportunistic pathogens, which requires consideration of atypical infections in valve-related complications. Sampling and analyzing vegetation and affected tissues are essential to identify new opportunistic pathogens and develop targeted preventive strategies.