Genomic diversity of several Corynebacterium species identified by amplification of the 16S-23S rRNA gene spacer regions

In order to investigate whether 16S-23S ribosomal DNA (rDNA) spacer region length polymorphisms are suitable for identification of Corynebacterium strains at the species level, the 16S-23S rDNA intergenic spacer region lengths of 128 strains belonging to 11 Corynebacterium species were studied by a PCR-based method, The lengths of the 16S-23S rDNA spacer regions varied from 394 to 585 bp, fragment lengths which are similar to those described for other genera, A single PCR profile was obtained for each of the following species: Corynebacterium renale, Corynebacterium urealyticum, Colynebacterium diphtheriae, Corynebacterium ulcerans, Corynebacterium pseudodiphtheriticum, and Corynebacterium kutscheri, In contrast, two and three PCR patterns were detected for Corynebacterium minutissimum, Corynebacterium striatum, Corynebacterium amycolatum, and Corynebacterium jeikeium, suggesting that genomic heterogeneity occurs in these four species, The 16S-23S rDNA spacer region length polymorphisms allowed us to discriminate among C, minutissimum, C.striatum, and C. amycolatum, three species that are frequently isolated and misidentified in clinical laboratories, Type strain Corynebacterium xerosis ATCC 373, which exhibited a PCR pattern similar to that of C. amycolatum strains classified in PCR group I, could nevertheless be discriminated from PCR group II (C. amycolatum) strains, as well as C. minutissimum and C. striatum strains, Type strain C. xerosis ATCC 373 and C. amycolatum strains classified in PCR group I could not be distinguished from strains belonging to C. diphtheriae, C. ulcerans, and C. pseudodiphtheriticum. The lipophilic species C. urealyticum and C.jeikeium, which are frequently encountered in clinical specimens, could be clearly distinguished from each other by this method, The use of 16S-23S spacer region length data determined by PCR-mediated amplification is suitable for identification of several Corynebacterium species, This rapid and easy method may be a useful identification tool for clinical microbiologists.