Cardiobacterium valvarum infective endocarditis and phenotypic/molecular characterization of 11 Cardiobacterium species strains.

Cardiobacterium valvarum is a newly recognized human pathogen related to infective endocarditis. Cardiobacterium species are, however, only rarely the aetiology of infective endocarditis. An infective endocarditis case is presented and, additionally, phenotypic and phylogenetic comparison of a further 10 collection strains, representing the two species within the genus, was performed. C. valvarum was isolated from the blood and DNA was present in valvular tissue (partial 16S rRNA gene analysis) from a 64-year-old man with infective endocarditis of the mitral valve, rupture of chordae and prolapse of pulmonary valves in addition to a fluttering excrescence. A mechanical mitral valve and neochordae were inserted successfully. Phenotypically, the two species within the genus Cardiobacterium resemble each other greatly. When using the Vitek 2 Neisseria-Haemophilus identification card, the reaction for phenylphosphonate was positive for all Cardiobacterium hominis strains, but negative for all C. valvarum strains, thereby separating the two species. The two species made up two separate clusters by phylogenetic examination using 16S rRNA gene sequence analysis.

Fastidious Gram-Negatives: Identification by the Vitek 2 Neisseria-Haemophilus Card and by Partial 16S rRNA Gene Sequencing Analysis.

Taxonomy and identification of fastidious Gram negatives are evolving and challenging. We compared identifications achieved with the Vitek 2 Neisseria-Haemophilus (NH) card and partial 16S rRNA gene sequence (526 bp stretch) analysis with identifications obtained with extensive phenotypic characterization using 100 fastidious Gram negative bacteria. Seventy-five strains represented 21 of the 26 taxa included in the Vitek 2 NH database and 25 strains represented related species not included in the database. Of the 100 strains, 31 were the type strains of the species. Vitek 2 NH identification results: 48 of 75 database strains were correctly identified, 11 strains gave `low discrimination´, seven strains were unidentified, and nine strains were misidentified. Identification of 25 non-database strains resulted in 14 strains incorrectly identified as belonging to species in the database. Partial 16S rRNA gene sequence analysis results: For 76 strains phenotypic and sequencing identifications were identical, for 23 strains the sequencing identifications were either probable or possible, and for one strain only the genus was confirmed. Thus, the Vitek 2 NH system identifies most of the commonly occurring species included in the database. Some strains of rarely occurring species and strains of non-database species closely related to database species cause problems. Partial 16S rRNA gene sequence analysis performs well, but does not always suffice, additional phenotypical characterization being useful for final identification.