Corynebacterium freneyi sp nov., α-glucosidase-positive strains related to Corynebacterium xerosis

Three coryneform strains from clinical specimens were studied. They belonged to the genus Corynebacterium, since they had type IV cell walls containing corynemycolic acids. They had phenotypic characteristics that included alpha -glucosidase, pyrazinamidase and alkaline phosphatase activities and fermentation of glucose, ribose, maltose and sucrose. These are the characteristics of Corynebacterium xerosis. Since this species is very rare in human pathology, the strains were studied in more detail by comparing the 16S-23S intergenic spacers, rDNA sequences and levels of DNA similarity of these three strains and those of the reference strains C. xerosis ATCC 373(T) and Corynebacterium amycolatum CIP 103452(T). According to DNA-DNA hybridization data, the three novel strains are members of the same species (level of DNA similarity > 72%). Phyllogenetic analysis revealed that these strains are closely related to C. xerosis and C. amycolatum, but DNA-relatedness experiments showed clearly that they constitute a distinct new species, with levels of DNA relatedness of less than 23% to C. xerosis ATCC 373(T) and less than 5% to C. amycolatum CIP 103452(T). Two other alpha -glucosidase-positive strains presenting the same biochemical characteristics were included in the study and proved to be C. amycolatum. This new species can be differentiated from C. xerosis and C. amycolatum strains by carbon source utilization, intergenic spacer region length profiles and some biochemical characteristics such as glucose fermentation at 42 degreesC and growth at 20 degreesC. The name Corynebacterium freneyi sp. nov. is proposed.