Nocardia niwae sp. nov., isolated from human pulmonary sources.

Members of the genus Nocardia are responsible for cutaneous, pulmonary and disseminated human infections. From 2003 to 2008, four nocardioform strains (W8027, W8681, W9071 and W9241(T)) were isolated from patients in the state of Florida, USA. Ribosomal gene sequencing analysis suggested that a novel species of the genus Nocardia had been isolated. These strains were subjected to a taxonomic analysis using a polyphasic approach. Phenotypic analyses included morphological 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. Phenotypic characteristics that differentiated the novel isolates from phylogenetically related species were growth at 45 °C, and three of the four 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 Nocardia araoensis DSM 44729(T), Nocardia arthritidis DSM 44731(T) and Nocardia beijingensis JCM 10666(T), 98.7 % to Nocardia amamiensis DSM 45066(T), 98.2 % to Nocardia pneumoniae JCM 12119(T) and 97.8 % to Nocardia takedensis JCM 13313(T). Analysis of partial gyrB gene sequences showed that the novel isolates had 95.4 % similarity to N. arthritidis DSM 44731(T), 95.3 % to Nocardia gamkensis DSM 44956(T), 94.4 % to N. pneumoniae JCM 12119(T), 93.8 % to Nocardia asiatica DSM 44668(T), 93.5 % to N. amamiensis DSM 45066(T), 93.4 % to N. beijingensis JCM 10666(T) and 93.2 % to N. araoensis DSM 44729(T). The DNA-DNA relatedness values between the four novel strains were 86-89 %; the relatedness value for strain W9241(T) compared with N. beijingensis JCM 10666(T) was 47 % and 46 % with N. araoensis DSM 44729(T), 44 % with N. arthritidis DSM 44731(T), 32 % with N. amamiensis DSM 45066(T) and 20 % with N. asiatica DSM 44668(T). The results of the taxonomic analysis suggested that the new isolates represent a novel species of the genus Nocardia for which the name Nocardia niwae sp. nov. is proposed. The type strain is W9241(T) (=DSM 45340(T)=CCUG 57756(T)).

Investigation of an apparent outbreak of Rhodococcus equi bacteremia.

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 Corynebacterium diphtheriae in domestic cats.

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.

Nocardia mikamii sp. nov., isolated from human pulmonary infections in the USA.

Four nocardioform bacterial strains isolated from clinical respiratory sources were characterized using a polyphasic taxonomic approach. On the basis of 16S rRNA gene sequence analyses, these strains were found to be 100 % similar to each other and were shown to belong to the genus Nocardia. Chemotaxonomic data [major menaquinone: ω-cyclic isoprene side chain MK-8(H4(cycl)); major polar lipids: diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides; major fatty acids: monounsaturated fatty acids with a considerable amount of tuberculostearic acid; and mycolic acids (52-62 carbon atoms)] were consistent with the assignment of the novel strains to the genus Nocardia. Comparative phylogenetic analysis of the 16S rRNA gene sequences showed that the novel strains were related to Nocardia cerradoensis DSM 44546(T) (99.8 %) and Nocardia aobensis JCM 12352(T) (99.6 %). Analysis of gyrB gene sequences showed these strains were related to N. aobensis (96.6 %) and to N. cerradoensis (96.3 %). The results suggest that gyrB gene sequencing is a more powerful tool than 16S rRNA gene sequencing for taxonomic identification within the genus Nocardia. DNA-DNA hybridization and physiological and biochemical tests supported the genotypic and phenotypic differentiation of the novel strains from related species. These data indicated that the new strains represent a novel species within the genus Nocardia, for which the name Nocardia mikamii sp. nov. is proposed, with strain W8061(T) (=DSM 45174(T)=JCM 15508(T)) as the type strain.

Gordonia araii infection associated with an orthopedic device and review of the literature on medical device-associated Gordonia infections.

Gordonia infections in humans are rare and usually affect immunocompromised patients. We present the first case of Gordonia araii infection associated with a medical device in an immunocompetent patient. Sequencing was required for conclusive identification. We compared our case to the 16 Gordonia species-associated medical device infections reported to date.

Assessment of ribosomal large-subunit D1-D2, internal transcribed spacer 1, and internal transcribed spacer 2 regions as targets for molecular identification of medically important Aspergillus species.

Molecular approaches are now being developed to provide a more rapid and objective identification of fungi compared to traditional phenotypic methods. Ribosomal targets, especially the large-subunit RNA gene (D1-D2 region) and internal transcribed spacers 1 and 2 (ITS1 and ITS2 regions), have shown particular promise for the molecular identification of some fungi. We therefore conducted an assessment of these regions for the identification of 13 medically important Aspergillus species: Aspergillus candidus, Aspergillus (Eurotium) chevalieri, Aspergillus (Fennellia) flavipes, Aspergillus flavus, Aspergillus fumigatus, Aspergillus granulosus, Aspergillus (Emericella) nidulans, Aspergillus niger, Aspergillus restrictus, Aspergillus sydowii, Aspergillus terreus, Aspergillus ustus, and Aspergillus versicolor. The length of ribosomal regions could not be reliably used to differentiate among all Aspergillus species examined. DNA alignment and pairwise nucleotide comparisons demonstrated 91.9 to 99.6% interspecies sequence identities in the D1-D2 region, 57.4 to 98.1% in the ITS1 region, and 75.6 to 98.3% in the ITS2 region. Comparative analysis using GenBank reference data showed that 10 of the 13 species examined exhibited a < or = 1-nucleotide divergence in the D1-D2 region from closely related but different species. In contrast, only 5 of the species examined exhibited a < or = 1-nucleotide divergence from sibling species in their ITS1 or ITS2 sequences. Although the GenBank database currently lacks ITS sequence entries for some species, and major improvement in the quality and accuracy of GenBank entries is needed, current identification of medically important Aspergillus species using GenBank reference data seems more reliable using ITS query sequences than D1-D2 sequences, especially for the identification of closely related species.