Culture-negative infective endocarditis due to Neisseria bacilliformis identified via 16S rRNA gene analysis from resected valve tissue: case report and review of the literature

Blood culture-negative infective endocarditis (BCNE) has a poorer prognosis than culture-positive cases. Thus, it is crucial to determine the pathogenic microorganism using molecular diagnostic techniques, in addition to conventional techniques, including cultures of blood and/or resected valve tissue. Herein, we report a case of culture-negative infective endocarditis (IE) caused by Neisseria bacilliformis, as identified by 16S rRNA analysis of valve tissue. N. bacilliformis a non-gonococcal and non-meningococcal Neisseria species that partially comprises the oropharyngeal microbiome, and reports of invasive infections have increased recently. We conducted a literature review of IE caused by N. bacilliformis and found that beta-lactam antibiotics were effective with a relatively favorable prognosis. To the best of our knowledge, this is the first case of culture-negative IE in which N. bacilliformis was identified via 16S rRNA analysis.