Genetic identification of members of the genus Corynebacterium at genus and species levels with 16S rDNA-targeted probes.

16S rRNA gene-targeted probes were designed for the identification of corynebacteria at the genus and species levels. The genus-specific probe hybridized all clinically important members of the genus Corynebacterium and could distinguish them from other coryneform bacteria and phylogenetically related high G+C% gram-positive bacteria, including Actinomyces, Rhodococcus, Gordona, Nocardia, Streptomyces, Brevibacterium and Mycobacterium. The species-specific probes for C. jeikeium and C. diphtheriae could differentiated these two species from other members of this genus. The probes were used to select corynebacteria among gram-positive clinical isolates which had been tentatively identified as corynebacteria by biochemical tests. We screened 59 strains with the genus-specific probe; 51 strains hybridized to the genus-specific probe, 8 did not. Of the 51 strains that hybridized to the genus-specific probe, 1 hybridized to the C. diphtheriae species probe and 13 hybridized to the C. jeikeium species probe. The 8 strains that did not hybridize to the genus probe were further characterized by analyzing cell wall diaminopimelic acid and partial 16S rRNA sequencing. The results indicated that these strains were distributed in the genera Arthrobacter and Brevibacterium.