16S ribosomal DNA sequence analysis distinguishes biotypes of Streptococcus bovis: Streptococcus bovis biotype II/2 is a separate genospecies and thepredominant clinical isolate in adult males

We characterized 22 human clinical strains of Streptococcus bovis by genoty pic (16S rRNA gene sequence analysis [MicroSeq]; Applied Biosystems, Foster City, Calif,) and phenotypic (API 20 Strep and Rapid ID32 Strep systems (b ioMerieux Vitek, Hazelton, Mo.) methods. The strains, isolated from blood, cerebrospinal fluid (CSF), and urine, formed two distinct 16S ribosomal DNA sequence clusters, Three strains which were associated with endocarditis u rinary tract infection (UTI), and sepsis clustered with the S, bovis type s train ATCC 33317 (cluster 1); other closely related type strains were S, eq uinus and S. infantarius. Nineteen strains clustered at a distance of about 2.5% dissimilarity to the S. bovis type strain (cluster 2) and were associ ated with central nervous system (CNS) disease in addition to endocarditis, UTI, and sepsis, All strains were distinct front S, gallolyticus. Within c luster 2, a single strain grouped with ATCC strain 43143 (cluster 2a) and m ay be phenotypically distinct, All the other strains formed a second subgro up (cluster 2b) that was biochemically similar to S, bovis biotype II/2 (ma nnitol negative and beta galactosidase, alpha galactosidase, beta glucuroni dase, and trehalose positive). The API 20 Strep system identified isolates of cluster 2b as S, bovis biotype II/2, those of cluster 1 as S, bovis biot ype II/1, and that of cluster 2a as S, bovis biotype I. There was an excell ent col,1,elation of biotype and genotype: S, bovis biotype II/2 isolates f orm a separate genospecies distinct from the S, bovis, S. gallolyticus, and S, infantarius type strains and are the most common isolates in adult male s.