Identification of Cardiobacterium hominis by broad-range bacterial polymerase chain reaction analysis in a case of culture-negative endocarditis

Culture-negative bacterial endocarditis may be attributed to fastidious microorganisms, prior institution of antibiotic treatment, or both. We describe a case of culture-negative endocarditis in which a modified Steiner stain revealed bacterial structures in the resected heart valve material. Prompted by this finding, broad-range polymerase chain reaction (PCR) amplification of small-subunit ribosomal DNA (16S rDNA) was performed, and Cardiobacterium hominis sequences were detected. This case demonstrates the usefulness of both the Steiner stain and broad-range direct molecular amplification as supplemental diagnostic tools in identification of otherwise unexplained infections.