Identification of enterococcal isolates by temperature gradient gel electrophoresis and partial sequence analysis of PCR-amplified 16S rDNA variable V6 regions

Based on partial sequence analysis of PCR-amplified 16S rDNA variable V6 re gions of 14 enterococcal type strains, Enterococcus faecalis, Enterococcus mundtii, Enterococcus gallinarum, Enterococcus avium, Enterococcus raffinos us and Enterococcus saccharolyticus showed characteristic sequence motifs w hich made it possible to separate them into six individual species lines. F urthermore, two species cluster groups could be identified, including (i) E nterococcus faecium, Enterococcus durans, Enterococcus hirae, Enterococcus malodoratus, and (ii) Enterococcus casseliflavus/Enterococcus flavescens, E nterococcus pseudoavium, Enterococcus dispar and Enterococcus sulfureus. Th ere were identical DNA sequences in the V6 region within each group. Tempor al temperature gradient gel electrophoresis (TTGE) of the PCR products from 16 type strains, 12 enterococcal reference strains and 8 clinical isolates revealed that a single nucleotide divergence in DNA sequences was sufficie nt for separation, identification and division of the studied enterococcal strains into corresponding TTGE profiles. It was concluded that partial DNA sequence analysis and TTGE profiling of PCR-amplified 16S rDNA variable V6 regions provide useful tools for the identification of clinically importan t Enterococcus spp.