Native Valve Endocarditis due to Corynebacterium striatum confirmed by 16S Ribosomal RNA Sequencing: A Case Report and Literature Review

Abstract

Corynebacterium species are non-fermentous Gram-positive bacilli that are normal flora of human skin and mucous membranes and are commonly isolated in clinical specimens. Non-diphtheriae Corynebacterium are regarded as contaminants when found in blood culture. Currently, Corynebacterium striatum is considered one of the emerging nosocomial agents implicated in endocarditis and serious infections. We report a case of native-valve infective endocarditis caused by C. striatum, which was misidentified by automated identification system but identified accurately by 16S ribosomal RNA sequencing, in a 55-year-old male patient. The patient had two mobile vegetations on his mitral valve, both of which had high embolic risk. Through surgical valve replacement and an antibiotic regimen, the patient recovered completely. In unusual clinical scenarios, C. striatum should not be simply dismissed as a contaminant when isolated from clinical specimens. The possibility of C. striatum infection should be considered even in an immunocompetent patient, and we suggest a genotypic assay, such as 16S rRNA sequencing, to confirm species identity.

Keywords: Corynebacterium; Endocarditis; RNA, Ribosomal, 16S.

Figure 1

Transesophageal echocardiogram findings. Large, hypermobile vegetations were attached to the middle scallop of the anterior (arrowhead) and posterior mitral valve leaflets (arrow), 10 mm and 8 mm, respectively. Vegetation on the posterior mitral valve leaflet showed a 7 mm lineal mobile structure, which indicates a high embolic risk. LA, left atrium; LV, left ventricle; Ao, aorta.