Haemophilus parainfluenzaeInfective Endocarditis Confirmed by 16S rRNA Sequence Analysis from Culture Negative Tissue

Blood culture-negative infective endocarditis (CNE) can be a diagnostic dilemma. Herein, we report a case of CNE caused by Haemophilus parainfluenzae identified only via 16S rRNA sequence analysis directly from valve tissue. A 17-year-old boy presented with high spiking fever for one month. Pansystolic murmur (Grade III) and vegetation (0.650.26 cm and 0.620.55 cm) on the anterior mitral valve leaflet via transesophageal echocardiogram suggested the diagnosis of infective endocarditis (IE). However, blood culture performed on admission was negative even after 2 weeks of incubation. Gram stain and culture of a direct tissue specimen failed to identify causative microorganism, while 16S rRNA gene sequences (548 bp) showed 100% identity with those of Haemophilus parainfluenzae (GenBank: FJ939586.1). The 16S rRNA sequence analysis with a direct tissue specimen might be useful in cases of CNE.