16S rRNA sequencing as a diagnostic tool in the identification of culture-negative endocarditis in surgically treated patients.

BACKGROUND AND AIM OF THE STUDY: Infective endocarditis (IE) is a worldwide problem, and at least one-third of cases are culture-negative despite the use of appropriate laboratory techniques. METHODS: A broad-range polymerase chain reaction (PCR) amplification was performed of the 16S rRNA gene, followed by single-strand sequencing for 26 surgically removed heart valves from patients with culture-negative endocarditis who had undergone valve repair or replacement. RESULTS: Two of the 26 patients were PCR-positive, and sequencing of the amplicon identified the etiological agent. Gram-stained smears of the heart valves were positive in both cases. Three of the remaining 24 cases which were negative by PCR also showed the presence of micro-organisms in Gram-stained smears. CONCLUSION: The study results emphasize that, in suspected IE cases when there is no growth in culture, a combination of microscopy and 16S rRNA sequencing can be used to identify the pathogen in excised valvular tissue.

Usefulness of 16S rDNA sequencing for the diagnosis of infective endocarditis caused by Corynebacterium diphtheriae.

We report a rare case of infective endocarditis caused by Corynebacterium diphtheriae in an 8-year-old boy, 2 years after a right ventricular outflow tract reconstruction with a bovine Contegra valved conduit. The patient recovered well after an RV-PA conduit enblock explantation and replacement with an aortic homograft with antibiotic treatment. All bacteriological cultures of excised tissue and blood were negative. The aetiological agent was identified as C. diphtheriae subsp. gravis by 16s rDNA sequencing.