rpoA could be a useful marker for identifying and classifying S. pneumoniae, selleck compound S. mitis, and S. oralis from closely related taxa. Family Streptococcaceae encompasses a broad range of gram-positive, catalase-negative, chain-forming coccus-shaped organisms. Currently, 92 species are recognized, many of which are associated with disease in humans and animals (http://www.bacterio.cict.fr). Among these group species, Streptococcus pneumoniae, the most common cause of pneumonia, bacterial meningitis, and nongonococcal urethritis in humans (Marrie et al., 1989; Hall et al., 1995; Fine et al., 1996), is frequently detected in the oral environment.

By contrast, two viridans group streptococci, Streptococcus mitis and Streptococcus oralis, which constitute major populations on oral soft tissues, cause dental caries and endocarditis (Willcox et al., 1988; Dyson et al., 1999). Precise discrimination

among the strains is essential for accurate diagnosis and treatment. Identification and classification of these organisms has long been considered difficult, however, because Nintedanib ic50 they have a close, common genetic ancestry (Whiley & Beighton, 1998; Whatmore et al., 2000; Mager et al., 2003). In recent years, molecular genetic analyses based on the 16S rRNA gene have provided new insights into the phylogenetic inter-relationships of many organisms (Bentley et al., 1991) and provided a powerful means for characterizing the level of species (Stackebrandt selleck chemicals et al., 1991; Fox et al, 1992; Stackebrandt & Goebel, 1994). However, the 16S rRNA gene molecule from members of closely related species may be so conserved that it cannot be used to distinguish between strains at the species level (Stackebrandt et al., 2002). Indeed, the nucleotide sequences of the 16S rRNA genes from S. mitis and S. oralis are almost (>99%) identical to that of S. pneumoniae, making the use of 16S rRNA gene alone insufficient for discrimination among these species (Suzuki et al., 2005). Housekeeping protein-coding genes are thought to

evolve faster than rRNA genes, and have been proposed as suitable phylogenetic markers for the identification and classification of bacteria (Palys et al., 1997, 2000). The aim of this study was to focus on the evaluation of the rpoA (RNA polymerase α subunit) gene for its reliability and usefulness as a new marker for discrimination among Streptococcus species. The 28 bacterial strains used in this study are listed in Table 1 and were obtained from the Korea Collection for Type Culture (KCTC, Daejeon, Korea), Culture Collection of Antibiotics Resistant Microbe (CCARM, Seoul, Korea), Korean Collection for Oral Microbiology (KCOM, Gwangju, Korea), Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ, Braunschweig Germany), and the American Type Culture Collection (ATCC, Manassas, VA). Each bacterial strain was grown on sheep blood agar plates (Asan Pharm Co.