Identification of coryneform bacterial isolates by ribosomal DNA sequence analysis

Identification of coryneform bacteria to the species level is important in certain circumstances for differentiating contamination and/or colonization from infection, which influences decisions regarding clinical intervention . However, methods currently used in clinical microbiology laboratories for the species identification of coryneform bacteria are often inadequate. We evaluated the MicroSeq 500 16S bacterial sequencing kit (Perkin-Elmer Bios ystems, Foster City, Calif,), which is designed to sequence the first 527 b p of the 16S rRNA gene for bacterial identification, by using 52 coryneform gram-positive bacilli from clinical specimens isolated from January throug h June 1993 at the Mayo Clinic, Compared to conventional and supplemented p henotypic methods, MicroSeq provided concordant results for identification to the genus level for all isolates, At the species level, MicroSeq provide d concordant results for 27 of 42 (64.3%) Corynebacterium isolates and 5 of 6 (83.3%) Corynebacterium-related isolates, respectively. Within the Coryn ebacterium genus, MicroSeq gave identical species-level identifications for the clinically significant Corynebacterium diphtheriae (4 of 4) and Coryne bacterium jeikeium (8 of 8), but it identified only 50.0% (15 of 30) of oth er species (P < 0.01). Four isolates from the genera Arthrobacter, Brevibac terium, and Microbacterium, which could not be identified to the species le vel by conventional methods, were assigned a species-level identification b y MicroSeq. The total elapsed time for running a MicroSeq identification wa s 15.5 to 18.5 h, These data demonstrate that the MicroSeq 500 16S bacteria l sequencing kit provides a potentially powerful method for the definitive identification of clinical coryneform bacterium isolates.