16S-23S Intergenic Spacer (ITS) Region Sequence Analysis: Applicability and Usefulness in Identifying Genera and Species Resembling Non-Hemolytic Streptococci

The species that are catalase-negative, gram-positive cocci and not belonging to streptococci or enterococci have become increasingly well characterized and the number of taxonomic entities steadily growing based on molecular taxonomic studies. This complicates their identification. 16S-23S Intergenic Spacer (ITS) region sequence analysis has proven to be a useful tool for species identification of the genera Streptococcus and Enterococcus. This study investigated the possibility of using ITS sequence analysis as a common tool for species identification within the genera Aerococcus, Abiotrophia, Alloiococcus, Dolosicoccus, Dolosigranulum, Facklamia, Granulicatella, Gemella, Ignavigranum, Leuconostoc, and Vagococcus. ITS sequences of 29 type strains and 103 well-characterized clinical strains were determined and BLAST analysis performed for species identification. All clinical strains were convincingly identified to the species level. Phylogenetic analysis showed distinct clustering of strains with the allocated species and the respective type strains. Thus, ITS sequence analysis was useful for species identification of bacteria belonging to the genera that are catalase-negative and gram-positive cocci. Potentially, ITS could be considered as the first line identification tool for the group of catalase-negative, gram-positive cocci, including nonhemolytic streptococci, enterococci and the taxons examined in this study.