Invasive pyogenic infection and infective endocarditis due to <i>Streptococcus anginosus</i>: a case report

<div><strong>Rationale:</strong> Streptococcus anginosus mostly colonizes the digestive and genitourinary system, including the oropharyngeal region. It commonly causes invasive pyogenic infection, but less likely causes infective endocarditis (IE).</div> <div><strong>Patient concerns:</strong> An 18-year-old woman who had an underlying mitral valve prolapse without mitral regurgitation presented to our hospital with low-grade fever, left leg weakness, and left abdominal pain. She was diagnosed with brain infarction and microabscess as well as IE. The patient totally recovered after the 6-week course of intravenous antibiotics.</div> <div><strong>Diagnosis:</strong> Brain magnetic resonance imaging revealed brain infarction and microabscess. Abdominal computed tomography revealed splenic and left renal infarction. Three sets of blood culture were positive for S anginosus. Transthoracic echocardiogram identified mitral valve prolapse with moderate eccentric mitral valve regurgitation, and a 0.3 × 0.6-cm vegetation was found on the left mitral valve. All of these results meet the modified Duke criteria.</div> <div><strong>Interventions:</strong> The abdominal pain and left leg weakness were improving after 2 weeks of intravenous antibiotics treatment. No neurological sequelae were noted after completing the 6-week course of medical treatment.</div> <div><strong>Outcomes:</strong> The patient was successfully treated and discharged after completing the 6-week intravenous antibiotics treatment.</div> <div><strong>Lessons:</strong> IE should be considered in young patients with native valve disease who have prolonged fever. Though S anginosus commonly causes invasive pyogenic infection, patients with native valve disease should be checked for IE.</div>