In this study, 16 human clinical isolates of Dietzia species previously misidentified as Rhodococcus equi were evaluated using phenotypic methods, including traditional and commercial (API Coryne) biochemical tests, antimicrobial susceptibility testing, and 16S rRNA gene and gyrB gene sequencing. Positive results for both the hydrolysis of adenine and Christie-Atkins-Munch-Petersen (CAMP) reaction allowed for differentiation between the Dietzia isolates and the type strain of Rhodococcus equi; however, traditional and commercial phenotypic profiles could not be used to reliably identify Dietzia species. The analysis of 16S rRNA gene and gyrB gene sequences could discriminate all Dietzia strains from the type strain of R. equi. Most Dietzia species had distinct 16S rRNA gene and gyrB gene sequences; however, the 16S rRNA gene sequences of the type strains of D. schimae and D. cercidiphylli were identical to D. maris and D. natronolimnaea, respectively. Based on comparative sequence analysis, five clinical isolates clustered with D. maris/D. schimae and nine with D. natronolimnaea/D. cercidiphylli. The two remaining isolates were found to be most closely related to the D. cinnamea/D. papillomatosis clade. Even though molecular analyses were not sufficiently discriminative to accurately identify all Dietzia species, the method was able to reliably identify isolates that were previously misidentified by phenotypic methods to the genus level.

During January to April 2007, hospital staff reported 3 patients with Rhodococcus equi bloodstream infections. Isolates were analyzed at the Centers for Disease Control and Prevention, Atlanta, GA, to confirm identification and to assess strain relatedness; 2 were R. equi but genetically distinct, and 1 was identified as Gordonia polyisoprenivorans. Rapid reference laboratory support prevented an unnecessary outbreak investigation.

Novel nontoxigenic Corynebacterium diphtheriae was isolated from a domestic cat with severe otitis. Contact investigation and carrier study of human and animal contacts yielded 3 additional, identical isolates from cats, although no evidence of zoonotic transmission was identified. Molecular methods distinguished the feline isolates from known C. diphtheriae.

Members of the genus Nocardia are responsible for cutaneous, pulmonary and disseminated human infections. From 2003 to 2008, four nocardioform strains (W8027, W8681, W9071, W9241T) were isolated from persons in the state of Florida, USA. Ribosomal gene sequencing analysis suggested that a novel Nocardia species had been isolated. These strains underwent polyphasic taxonomic analysis. Phenotypic analyses included morphologic examination, biochemical profiling and antimicrobial susceptibility testing. Molecular studies included 16S rRNA and DNA gyrase B subunit (gyrB) gene sequence analyses and DNA-DNA hybridization. Phylogenetic neighbours were determined through 16S rRNA and gyrB gene sequence analyses. Differential phenotypic characteristics of the novel Nocardia species compared to phylogenetically related species were growth at 45C and 3 out of 4 novel strains utilized L-rhamnose. The antimicrobial profiles could not reliably distinguish the novel species from related nocardiae. Analysis showed that the 16S rRNA gene sequences of the four novel isolates were identical. The BLAST analysis of the near full length 16S rRNA gene showed 99.2 % sequence similarity to N. araoensis DSM 44729T, N. arthritidis DSM 44731T and N. beijingensis JCM 10666 T, 98.7 % to N. amamiensis DSM 45066T, 98.2 % to N. pneumoniae JCM 12119T and 97.8 % to N. takedensis JCM 13313T; the analysis of partial gyrB gene sequences showed 95.4 % similarity to N. arthritidis DSM 44731T, 95.3 % to N. gamkensis DSM 44956T, 94.4 % to N. pneumoniae JCM 12119T, 93.8 % to asiatica DSM44668T, 93.5 % to N. amamiensis DSM 45066T, 93.4 % to N. beijingensis JCM 10666 T and 93.2 % to N. araoensis DSM 44729T. The DNA-DNA hybridization percentages among the four novel strains were 86-89 %; the hybridization percentages of W9241T compared to N. beijingensis JCM 10666T was 47 %, to N. araoensis DSM 44729T was 46 %, to N. arthritidis DSM 44731T was 44 %, to N. amamiensis DSM 45066T was 32 % and to N. asiatica DSM 44668T was 20 %. The results of our polyphasic taxonomic analysis suggested that a novel species of Nocardia was identified for which we propose the name Nocardia niwae sp. nov. The type strain is W9241T ( = DSM 45340T = CCUG 57756T).

Four nocardioform bacteria were isolated from clinical respiratory sources (W7467, W7811, W8061T and W9013) in the United States. Macroscopic examination showed scant aerial hyphae and beige-red substrate hyphae. They showed chemotaxonomic markers that were consistent with the classification of Nocardia: i.e., meso-diaminopimelic acid; arabinose and galactose as diagnostic sugars; the phospholipids diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides; a menaquinone with a omega-cyclic isoprene side chain MK-8(H4cycl.); a fatty acid pattern composed of unbranched saturated and monounsaturated fatty acids with considerable amount of tuberculostearic acid; and mycolic acids comprising 52 to 62 carbon atoms with three principal mycolic acids which were mono- and polyunsaturated showing a chain length of C54, C56 and C58. 16S rRNA gene sequence data and phenotypic characters showed they were most closely related to Nocardia aobensis (DSM 44805T ). The G+C content was 68.3 mol %. Analysis of a 1,245-bp fragment of gyrB gene showed a clade separate from N. aobensis and was supported by the DNA relatedness of 67 % of W8061T to N. aobensis. These data indicated that the novel isolates represent a new species within the genus Nocardia, for which the name Nocardia mikamii sp. nov. is proposed, with W8061T (DSM 45174T = JCM 15508T) designated as the type strain.