Identification of some charcoal-black-pigmented CDC fermentative coryneform group 4 isolates as Rothia dentocariosa and some as Corynebacterium aurimucosum: proposal of Rothia dentocariosa emend. Georg and Brown 1967, Corynebacterium aurimucosum emend. Yassin et al. 2002, and Corynebacterium nigricans Shukla et al. 2003 pro synon. Corynebacterium aurimucosum.

Sixty-three clinical isolates of charcoal-black-pigmented, gram-positive coryneform rods were received for identification by the Centers for Disease Control and Prevention (CDC) and were provisionally designated CDC fermentative coryneform group 4 (FCG4). Forty-five of these were characterized by morphological, physiologic, antimicrobial susceptibility, cellular fatty acids, 16S rRNA gene sequencing, and DNA-DNA hybridization analyses. Nitrate reduction, cellular fatty acid analysis, 16S rRNA gene sequencing, and DNA-DNA hybridization studies segregated these strains into two groups: FCG4a (8 strains) and FCG4b (37 strains). The FCG4a strains, only one of which was from a female genitourinary source, produced cellular fatty acid and biochemical profiles similar to those observed with reference strains of Rothia dentocariosa and Rothia mucilaginosa, while the FCG4b strains were similar to Corynebacterium species. DNA-DNA hybridization analysis demonstrated species-level relatedness among six FCG4a tested strains and showed that they were a charcoal-black-pigmented variant of R. dentocariosa. Sixteen isolates of the FCG4b group, mainly from female genitourinary tract specimens, as well as the type strains of two recently named species, Corynebacterium aurimucosum and Corynebacterium nigricans, were shown by DNA-DNA hybridization analysis and the sequencing of the 16S rRNA gene to be related at the species level and unrelated to the type strain of R. dentocariosa; therefore, the Corynebacterium-like strains were classified as a charcoal-black-pigmented variant of C. aurimucosum, because this name has nomenclatural priority over C. nigricans. These findings indicate that FCG4 represents a heterogeneous group that contains pigmented variants of both R. dentocariosa and C. aurimucosum; hence, the descriptions of both R. dentocariosa and C. aurimucosum have been amended to include charcoal-black-pigmented variants, and C. nigricans is a pro synonym of C. aurimucosum.

Taxonomic variation in the Mycobacterium fortuitum third biovariant complex: description of Mycobacterium boenickei sp. nov., Mycobacterium houstonense sp. nov., Mycobacterium neworleansense sp. nov. and Mycobacterium brisbanense sp. nov. and recognition of Mycobacterium porcinum from human clinical isolates.

The Mycobacterium fortuitum third biovariant complex (sorbitol-negative and sorbitol-positive) contains unnamed taxa first characterized in 1991. These organisms can cause respiratory infections, a spectrum of soft tissue and skeletal infections, bacteraemia and disseminated disease. To evaluate this group of organisms, clinical reference isolates and the type strains of M. fortuitum third biovariant complex sorbitol-negative (n = 21), M. fortuitum third biovariant complex sorbitol-positive (n = 3), M. fortuitum (n = 3), Mycobacterium peregrinum (pipemidic acid-susceptible) (n = 1), Mycobacterium porcinum (n = 1), Mycobacterium senegalense (n = 2) and Mycobacterium septicum (n = 1) were characterized by using conventional phenotypic (morphological, physiological and antimicrobial susceptibilities), chemotaxonomic (HPLC and cellular fatty acids) and genotypic [RFLP of the rRNA gene (ribotyping), PCR-RFLP of a 439 bp segment of the 65 kDa hsp gene (PCR restriction analysis) and 16S rRNA gene sequence] analysis, DNA G + C content and DNA-DNA relatedness analyses. The results of these studies indicated that the strains comprised M. porcinum (n = 13), M. septicum (n = 1) and four novel closely related genetic groups within the M. fortuitum third biovariant complex: Mycobacterium boenickei sp. nov. (n = 6), Mycobacterium houstonense sp. nov. (n = 2), Mycobacterium neworleansense sp. nov. (n = 1) and Mycobacterium brisbanense sp. nov. (n = 1), with type strains ATCC 49935T (= W5998T = DSM 44677T), ATCC 49403T (= W5198T = DSM 44676T) ATCC 49404T (= W6705T = DSM 44679T) and ATCC 49938T (= W6743T = DSM 44680T), respectively.