What does 16S rRNA gene-targeted next generation sequencing contribute to the study of infective endocarditis in valve tissue?

Infective endocarditis (IE) is a severe and life-threatening disease. Identification of infectious etiology is essential for establishing the appropriate antimicrobial treatment and decreasing mortality. The aim of this study was to explore potential utility of metagenomics for improving microbiological diagnosis of IE. In this work, next-generation sequencing (NGS) of V3-V4 region of the 16S rRNA gene was performed in 27 heart-valve tissues (18 natives, 5 intravascular devices, and 4 prosthetics) of patients diagnosed by IE. Initial microbiological diagnosis, blood culture (BC) and/or PCR, was compared with NGS-based diagnosis. Metagenomics matched with conventional techniques diagnosis in 24/27 cases (88.9%). The same bacterial family was assigned to 24 cases, the same genus to 23 cases, and the same specie for 13 cases. In 22 of them, the etiological agent was represented by percentages >99% of the reads and in two by ~70%. Staphylococcus aureus was detected in a previously undiagnosed patient, making the microbiological diagnosis possible in one more sample than with previously used techniques. The remaining two patients showed no coincidence between traditional and NGS microbiological diagnoses. Minority records verified mixed infections in four cases and suggested confections in two cases, supported by clinical data. In conclusion: 16S rRNA gene-targeted NGS allowed to diagnose one case of IE without microbiological entity based on traditional techniques. However, the application of metagenomics to the study of IE in resected heart valves provides no benefits in comparison with BC and/or PCR. More studies are needed before implementation of NGS for the diagnosis of IE.