Staircase electrophoresis profiles of stable low-molecular-weight RNA--a new technique for yeast fingerprinting.
(17/694)
Staircase electrophoresis (SCE) in polyacrylamide gels was used to analyse the stable low-molecular-weight (LMW) RNA profiles of several yeast species and genera. As in prokaryotes, this new electrophoretic technique results in good separation of molecules forming LMW RNA profiles in yeasts. In this study it is reported that, while LMW RNA profiles in prokaryotes include only 5S rRNA, and class 2 and class 1 tRNA, these profiles in eukaryotes also include 5.8S rRNA. Differences in the number and distribution of RNA bands in these profiles allowed identification of differences among the yeast species and genera assayed. LMW RNAs, analysed by SCE, provide a yeast fingerprint that allows them to be clearly differentiated and will in the future enable the rapid assignment of yeast isolates to already described species and the detection of new ones. (+info)
Trichosporon veenhuisii sp. nov., an alkane-assimilating anamorphic basidiomycetous yeast.
(18/694)
A morphological and physiological description of an alkane-assimilating anamorphic basidiomycetous yeast species, named Trichosporon veenhuisii, is presented. The ability to assimilate several aliphatic and aromatic compounds as sole source of carbon and energy is reported. The phylogenetic position within the genus, based on nuclear base sequencing of the D1/D2 region of the large subunit of rDNA, is discussed. The type strain is CBS 7136T. (+info)
Candida tartarivorans sp. nov., an anamorphic ascomycetous yeast with the capacity to degrade L(+)- and meso-tartaric acid.
(19/694)
An undescribed anamorphic yeast species of ascomycetous affinity, for which the name Candida tartarivorans is proposed, was isolated from dried wine lees in Portugal using a selective medium with L(+)-tartaric acid as the sole source of carbon and energy. The single isolate (IGC 4854T) showed the following characteristics: sympodial holoblastic conidiogenesis, absence of asci with ascospores, a negative colour reaction with Diazonium Blue B, production of elaborate pseudomycelium and ability to grow with inositol as sole source of carbon. Analysis of the physiological data pointed to a close relationship with other inositol-assimilating taxa, namely the genera Arxula, Stephanoascus, Sympodiomyces, Zygoascus and selected Candida species. Comparative analysis of the D1/D2 variable domain of the 26S rRNA gene of all available sequences for ascomycetous yeasts showed that strain IGC 4854T did not match with any other species in the database. The closest relative was Candida auringiensis Santa Maria, but the two species differed in 24 nucleotide positions. A description of the new species is given. (+info)
Oral colonization, phenotypic, and genotypic profiles of Candida species in irradiated, dentate, xerostomic nasopharyngeal carcinoma survivors.
(20/694)
The aim of this study was to investigate oral yeast colonization and oral yeast strain diversity in irradiated (head and neck), dentate, xerostomic individuals. Subjects were recruited from a nasopharyngeal carcinoma clinic and were segregated into group A (age, <60 years [n = 25; average age +/- standard deviation (SD), 48 +/- 6 years; average postirradiation time +/- SD, 5 +/- 5 years]) and group B (age, >/=60 years [n = 8; average age +/- SD, 67 +/- 4 years; average postirradiation time +/- SD, 2 +/- 2 years]) and were compared with age- and sex-matched healthy individuals in group C (age, <60 years [n = 20; average age +/- SD, 44 +/- 12 years] and group D (age, >/=60 years [n = 10; average age, 70 +/- 3 years]). Selective culture of oral rinse samples was carried out to isolate, quantify, and speciate yeast recovery. All test subjects underwent a 3-month comprehensive oral and preventive care regimen plus topical antifungal therapy, if indicated. A total of 12 subjects from group A and 5 subjects from group B were recalled for reassessment of yeast colonization. Sequential (pre- and posttherapy) Candida isolate pairs from patients were phenotypically (all isolate pairs; biotyping and resistotyping profiles) and genotypically (Candida albicans isolate pairs only; electrophoretic karyotyping by pulsed-field gel electrophoresis, restriction fragment length polymorphism [RFLP], and randomly amplified polymorphic DNA [RAPD] assays) evaluated. All isolates were Candida species. Irradiated individuals were found to have a significantly increased yeast carriage compared with the controls. The isolation rate of Candida posttherapy remained unchanged. A total of 9 of the 12 subjects in group A and 3 of the 5 subjects in group B harbored the same C. albicans or Candida tropicalis phenotype at recall. Varying degrees of congruence in the molecular profiles were observed when these sequential isolate pairs of C. albicans were analyzed by RFLP and RAPD assays. Variations in the genotype were complementary to those in the phenotypic characteristics for some isolates. In conclusion, irradiation-induced xerostomia seems to favor intraoral colonization of Candida species, particularly C. albicans, which appeared to undergo temporal modifications in clonal profiles both phenotypically and genotypically following hygienic and preventive oral care which included topical antifungal therapy, if indicated. We postulate that the observed ability of Candida species to undergo genetic and phenotypic adaptation could strategically enhance its survival in the human oral cavity, particularly when salivary defenses are impaired. (+info)
Retrospective identification and characterization of Candida dubliniensis isolates among Candida albicans clinical laboratory isolates from human immunodeficiency virus (HIV)-infected and non-HIV-infected individuals.
(21/694)
Fungal opportunistic infections, and in particular those caused by the various Candida species, have gained considerable significance as a cause of morbidity and, often, mortality. The newly described species Candida dubliniensis phenotypically resembles Candida albicans so closely that it is easily misidentified as such. The present study was designed to determine the frequency at which this new species is not recognized in the clinical laboratory, to determine the patient populations with which C. dubliniensis is associated, to determine colonization versus infection frequency, and to assess fluconazole resistance. Over a 2-year period, 1,251 isolates that were initially identified as C. albicans by a hospital clinical laboratory were reevaluated for C. dubliniensis by inability to grow at 45 degrees C, colony color on CHROMagar Candida medium, coaggregation assay with Fusobacterium nucleatum, and sugar assimilation profiles (API 20C AUX yeast identification system). A total of 15 (1.2%) isolates from 12 patients were identified as C. dubliniensis. Ten of the patients were found to be immunocompromised (these included patients with human immunodeficiency virus infection or AIDS, cancer patients receiving chemotherapy, and patients awaiting transplantation). Thirteen isolates were highly susceptible to fluconazole (MIC, <0.5 microgram/ml). Three isolates from one patient, genotypically confirmed as the same strain, showed variable susceptibility to fluconazole. The first isolate was susceptible, whereas the other two isolates were dose-dependent susceptible (MIC, 16.0 microgram/ml). These data confirm the close association of C. dubliniensis with immunocompromised states and that increased fluconazole MICs may develop in vivo. This study emphasizes the importance of screening germ-tube-positive yeasts for the inability to grow at 45 degrees C followed by confirmatory tests in order to properly identify this species. (+info)
Three new species in the Saccharomyces sensu stricto complex: Saccharomyces cariocanus, Saccharomyces kudriavzevii and Saccharomyces mikatae.
(22/694)
On the basis of genetic analysis, molecular karyotyping and sequence analyses of the 18S rRNA and internal transcribed spacer (ITS) region, three new Saccharomyces species are described, Saccharomyces cariocanus (with type strain NCYC 2890T), Saccharomyces kudriavzevii (with type strain NCYC 2889T) and Saccharomyces mikatae (with type strain NCYC 2888T). Genetic and molecular analyses did not confirm the previously observed conspecificity of Saccharomyces paradoxus and S. cariocanus. The latter species exhibits postzygotic isolation from representative strains from all known geographical populations of S. paradoxus: European, Far-East Asian, North American and Hawaiian. (+info)
Strain identification of Trichophyton rubrum by specific amplification of subrepeat elements in the ribosomal DNA nontranscribed spacer.
(23/694)
Trichophyton rubrum is the commonest cause of dermatophytosis of skin and nail tissue. Molecular characterization of the T. rubrum ribosomal DNA nontranscribed-spacer region revealed two novel tandemly repetitive subelements (TRSs): TRS-1, containing a 27-bp palindromic sequence, and TRS-2. Specific amplification of TRS-1 produced strain-characteristic banding patterns (PCR types), with 21 TRS-1 PCR types recognized from 101 clinical isolates. Four simple patterns representing 1 to 4 copies of TRS-1 accounted for 75 (75%) of all 101 strains, whereas more complex patterns were observed for 21 (20%) of the 101 isolates. The copy number of TRS-2 was 0 to 3 repeats per cistron, with a majority of isolates having two copies of this element. Eleven isolates were polymorphic for TRS-2, and in combination, 23 separate PCR types were recognized by amplification of both TRS-1 and TRS-2. The PCR patterns from both elements were stable and reproducible. Elements with homology to TRS-1 were present in three phylogenetically related species, Trichophyton violaceum, Trichophyton gourvilii, and Trichophyton soudanense, but these elements were not identified in other dermatophyte taxa. There was no clear correlation of PCR type with specimen (skin or nail tissue), but certain PCR types appeared to show a bias in geographic distribution. This new method of typing T. rubrum will enable important questions about pathogenesis and epidemiology of this fungus to be addressed. (+info)
Comparative genotyping of Candida albicans bloodstream and nonbloodstream isolates at a polymorphic microsatellite locus.
(24/694)
Molecular typing studies have shown that the predominant form of reproduction of Candida albicans is clonal and that, in a majority of situations, persistent or recurrent infections are due to a unique strain. Characterization of distinct subpopulations and correlation with clinical features may thus be important to understanding the pathogenesis of candidiasis. In a clonal model, a unique polymorphic marker may identify populations with different biological properties. We therefore compared 48 bloodstream isolates and 48 nonbloodstream matched strains of C. albicans at the elongation factor 3-encoding gene (CEF3) polymorphic microsatellite locus of C. albicans. Sizing of the alleles was performed by automated capillary electrophoresis. A new, 137-bp allele was characterized, and seven nondescribed combinations were observed, resulting in 15 and 11 distinct CEF3 profiles in bloodstream and control strains, respectively. Genotypes 126-135, 130-136, and 131-131 accounted for 60.4% of both bloodstream and control strains. Four bloodstream isolates but no control strains displayed the 135-135 combination. None of the other genotypes was present at an increased frequency in bloodstream isolates. Bloodstream and nonbloodstream strains of C. albicans thus have a heterogeneous structure at the CEF3 locus, with three major and multiple minor allelic combinations. (+info)