Quahogging in a Marine Habitat: An Extremely Rare Source of an Organism to Cause Endocarditis

A 66-year-old man with a history of apical variant hypertrophic cardiomyopathy, heart failure with preserved ejection fraction (HFpEF), severe pulmonary hypertension, and prior Group B streptococcal mitral valve endocarditis four months before, presented with generalized body shakes and urinary incontinence. Computed tomography angiography revealed an acute left M1 occlusion. The patient underwent mechanical thrombectomy. Within 24 hours of presentation, he developed hypotension, tachycardia, and fever. Infectious workup revealed a leukocytosis. One out of two sets of blood cultures revealed bacteremia with Shewanella algae. A transthoracic echocardiogram revealed a large mitral valve vegetation with multiple mobile components portending a high thromboembolic risk, as evidenced by his acute presentation with multiple embolic infarcts. He was diagnosed with infectious endocarditis caused by Shewanella algae, a rare marine environment pathogen. He was treated with ciprofloxacin 750 mg twice daily orally and meropenem 2 g every eight hours intravenously with an initial decrease in the mitral valve vegetation size. He was discharged on ceftriaxone 2g and ciprofloxacin 750mg every 12 hours for a total of six weeks from his first negative blood cultures. He was monitored through transthoracic echocardiography as he continued medical management with levofloxacin 750 mg daily. Six months after his discharge from the hospital he developed worsening heart failure and elected to pursue comfort measures only.