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Biomedical subjects

Teun Boekhout

Publications and source records attributed to Teun Boekhout.

26 records · Page 2Linked to original sources

Co-isolation of Trichosporon inkin and Candida parapsilosis from a scalp white piedra case.

White piedra is a rare fungal infection of the hair shaft characterized by small, firm, irregular white-brown nodules. The infection is caused by basidiomycetous yeasts in the genus Trichosporon. We report a case of a 28-year-old female patient who acquired the infection in Qatar. In this case, the scalp was the only site affected, but infection at that site was extensive. The hair had a Saccharomyces-like yeast odor and appeared to be beaded, with light-brown nodules of varying sizes up to 2 mm long. Trichosporon sp. accompanied by Candida parapsilosis grew out along hair shafts planted in primary isolation media. Molecular identification of the Trichosporon carried out by analyzing the 26S ribosomal gene gave a 100% match with Trichosporon inkin, a major cause of pubic white piedra. The patient was treated with daily applications of ketoconazole shampoo followed by econazole shampoo and cream, and was considered clinically and mycologically cured after 2 months. Novel findings in the present case are the first identification of T. inkin as an agent of scalp white piedra, and the heavy outgrowth of C. parapsilosis from the concretions, although in the latter case it is not clear if the co-occurring yeast was etiologically contributory to the pathogenesis of the white piedra.

Adult↗

Identification and typing of Malassezia species by amplified fragment length polymorphism and sequence analyses of the internal transcribed spacer and large-subunit regions of ribosomal DNA.

Malassezia yeasts are associated with several dermatological disorders. The conventional identification of Malassezia species by phenotypic methods is complicated and time-consuming, and the results based on culture methods are difficult to interpret. A comparative molecular approach based on the use of three molecular techniques, namely, amplified fragment length polymorphism (AFLP) analysis, sequencing of the internal transcribed spacer, and sequencing of the D1 and D2 domains of the large-subunit ribosomal DNA region, was applied for the identification of Malassezia species. All species could be correctly identified by means of these methods. The results of AFLP analysis and sequencing were in complete agreement with each other. However, some discrepancies were noted when the molecular methods were compared with the phenotypic method of identification. Specific genotypes were distinguished within a collection of Malassezia furfur isolates from Canadian sources. AFLP analysis revealed significant geographical differences between the North American and European M. furfur strains.

Animals↗

Novel anamorphic mite-associated fungi belonging to the Ustilaginomycetes: Meira geulakonigii gen. nov., sp. nov., Meira argovae sp. nov. and Acaromyces ingoldii gen. nov., sp. nov.

Three novel mite-associated basidiomycetous species are described in two new anamorph genera as Meira geulakonigii gen. nov., sp. nov. (type CBS 110052(T)=NRRL Y-27483(T)=AS 004(T)), Meira argovae sp. nov. (type CBS 110053(T)=NRRL Y-27482(T)=AS 005(T)) and Acaromyces ingoldii gen. nov., sp. nov. (type CBS 110050(T)=NRRL Y-27484(T)=AS 001(T)). Morphologically, these fungi are similar to the yeast-like fungi classified in the Ustilaginales, such as Pseudozyma species. However, analysis of the D1/D2 domain of the LSU rDNA suggests that they belong to two different lineages within the Exobasidiomycetidae of the Ustilaginomycetes (Basidiomycota). Furthermore, these fungi may be of interest for the biocontrol of mites, as they reduced mite numbers by approximately 80 % after inoculation.

Animals↗

Reclassification of the Sporobolomyces roseus and Sporidiobolus pararoseus complexes, with the description of Sporobolomyces phaffii sp. nov.

More than 50 ballistoconidium-forming yeast strains, isolated from plant leaves collected in Yunnan, China, were identified as Sporobolomyces roseus Kluyver & van Niel by conventional methods. However, comparison of the internal transcribed spacer (ITS) region and 265 rDNA D1/D2 domain sequences indicated that these strains represented more than one species. Type or authentic strains of the synonyms of Sporobolomyces roseus and the closely related species Sporidiobolus pararoseus Fell & Tallman were employed in the rDNA sequence comparison. Sporobolomyces boleticola Ramírez, Sporobolomyces pollaccii Verona & Ciferri, Sporobolomyces roseus var. madurae Janke and Torulopsis somala Verona were confirmed to be conspecific with Sporobolomyces roseus. Another synonym of this species, Sporobolomyces salmoneus Derx, was located together with Sporobolomyces marcillae Santa Maria in a separate clade. Two synonyms of Sporidiobolus pararoseus, Sporobolomyces carnicolor Yamasaki & Fujii (nom. inval.) and Sporobolomyces japonicus Iizuka & Goto, were revealed to represent two distinct species. The name Sporobolomyces carnicolor is validated, with strain CBS 4215(T) as the type strain. A novel species represented by five of the selected Yunnan strains was confirmed, for which the name Sporobolomyces phaffii sp. nov. is proposed (type strain CH 2.052(T) = AS 2.2137(T) = JCM 11491(T) = CBS 9129(T)). This study also indicates that yeast species with similar ITS sequences may have quite different D1/D2 sequences.

Base Sequence↗

Molecular identification and genetic diversity within species of the genera Hanseniaspora and Kloeckera.

Three molecular methods, RAPD-PCR analysis, electrophoretic karyotyping and RFLP of the PCR-amplified ITS regions (ITS1, ITS2 and the intervening 5.8S rDNA), were studied for accurate identification of Hanseniaspora and Kloeckera species as well as for determining inter- and intraspecific relationships of 74 strains isolated from different sources and/or geographically distinct regions. Of these three methods, PCR-RFLP analysis of ITS regions with restriction enzymes DdeI and HinfI is proposed as a rapid identification method to discriminate unambiguously between all six Hanseniaspora species and the single non-ascospore-forming apiculate yeast species Kloeckera lindneri. Electrophoretic karyotyping produced chromosomal profiles by which the seven species could be divided into four groups sharing similar karyotypes. Although most of the 60 strains examined exhibited a common species-specific pattern, a different degree of chromosomal-length polymorphism and a variable number of chromosomal DNA fragments were observed within species. Cluster analysis of the combined RAPD-PCR fingerprints obtained with one 10-mer primer, two microsatellite primers and one minisatellite primer generated clusters which with a few exceptions are in agreement with the groups as earlier recognized in DNA-DNA homology studies.

Animals↗

Fast, noninvasive method for molecular detection and differentiation of Malassezia yeast species on human skin and application of the method to dandruff microbiology.

Malassezia fungi have been the suspected cause of dandruff for more than a century. Previously referred to as Pityrosporum ovale, Pityrosporum orbiculare, or Malassezia, these fungi are now known to consist of at least seven Malassezia species. Each species has a specific ecological niche, as well as specific biochemical and genetic characteristics. Malassezia yeasts have fastidious culture conditions and exceedingly different growth rates. Therefore, the results of surveys of Malassezia based on culture methods can be difficult to interpret. We developed a molecular technique, terminal fragment length polymorphism analysis, to more accurately survey the ecology of Malassezia yeasts without bias from culture. This technique involves fluorescent nested PCR of the intergenic transcribed spacer (ITS) ITS I and ITS II region ribosomal gene clusters. All known Malassezia species can be differentiated by unique ITS fragment lengths. We have used this technique to directly analyze scalp samples from subjects enrolled in a demographic scalp health study. Results for subjects assigned composite adherent scalp flaking scores (ASFS) <10 were compared to those for subjects assigned composite ASFS >24. Malassezia restricta and M. globosa were found to be the predominant Malassezia species present in both groups. Importantly, we found no evidence of M. furfur in either group, indicating that M. furfur can be eliminated as the causal organism for dandruff. Both groups also showed the presence of non-Malassezia fungi. This method, particularly when it is used in combination with existing fungal ITS databases, is expected to be useful in the diagnosis of multiple other fungal infections.

DNA, Fungal↗

Hybrid genotypes in the pathogenic yeast Cryptococcus neoformans.

Amplified fragment length polymorphism (AFLP) genotyping of isolates of the pathogenic fungus Cryptococcus neoformans suggested a considerable genetic divergence between the varieties C. neoformans var. neoformans and C. neoformans var. grubii on the one hand versus C. neoformans var. gattii on the other. This divergence is supported by additional phenotypic, biochemical, clinical and molecular differences. Therefore, the authors propose the existence of two species, C. neoformans (Sanfelice) Vuillemin and C. bacillisporus Kwon-Chung, which differ in geographical distribution, serotypes and ecological origin. Within each species three AFLP genotypes occur, which differ in geographical distribution and serotypes. Differences in ecological origin (AIDS patients, non-AIDS patients, animals or the environment) were found to be statistically not significant. In C. neoformans as well as in C. bacillisporus one of the genotypes represented a hybrid. The occurrence of hybridization has consequences for the reproductive biology of the species, as new genotypes with altered virulence or susceptibility to antifungal drugs may arise through the exchange of genetic material.

AIDS-Related Opportunistic Infections↗

Structural differences between two types of basidiomycete septal pore caps.

The septal pore cap (SPC) of Trichosporon sporotrichoides CBS 8245 is vesicular-tubular, connected with flat-tubular endoplasmic reticulum (ER), and stains densely with zinc/iodine/osmium tetroxide, as does the ER. The SPC of Schizophyllum commune CBS 340.81 is more complex, about 600 nm in diameter, with perforations of 80-120 nm diameter, and stains less densely with zinc/iodine/osmium tetroxide than the ER. In high-pressure frozen and freeze-substituted hyphae of T. sporotrichoides the ER is present parallel to the dolipore septa, and electron-dense material occurs opposite the septal pore channel; the SPC rarely showed smooth vesicular-tubular membranes, suggesting that this is an ephemeral function of the SPC. The SPC of S. commune has a smooth outer and inner membrane, which enclose a matrix with a palisade-like substructure. A thin layer of electron-dense material covers the inner surface of the SPC of S. commune, from which beaded filamentous structures connect the SPC and the pore-occluding material. These filamentous structures may maintain the intracellular position of the SPC and possibly play a role in plugging the septal pore channel. The septal pore swellings of T. sporotrichoides contain more 1,6-beta-glucan than the septum, and intracellular glucans are also present near the septal pore channel. This cytosolic 1,6-beta-glucan in T. sporotrichoides may serve as a matrix to keep the tubular membranous structures of the SPC together. In contrast, 1,6-beta-glucan is not observed in the SPC and in the pore-occluding material of S. commune, and hyphal septa of this species show less labelling of 1,6-beta-glucan than the septal swelling. The evolutionary transition from simple to more complex types of SPCs may have resulted in a requirement for different components to maintain the morphological integrity and cell biological function.

Basidiomycota↗