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Molecular differentiation of seven Malassezia species.

ABSTRACT: A system based on PCR and restriction endonuclease analysis was developed to distinguish the seven currently recognized Malassezia species. Seventy-eight strains, including authentic culture collection strains and routine clinical isolates, were investigated for variation in the ribosomal DNA repeat units. Two genomic regions, namely, the large subunit of the ribosomal gene and the internal transcribed spacer (ITS) region, were amplified by PCR, and products were digested with restriction endonucleases. The patterns generated were useful in identification of five out of seven Malassezia species. M. sympodialis was readily distinguishable in that its ITS region yielded a 700-bp amplified fragment, whereas the other six species yielded an 800-bp fragment. M. globosa and M. restricta were very similar in the regions studied and could be distinguished only by performing a hot start-touchdown PCR on primers for the beta-tubulin gene. Primers based on the conserved areas of the Candida cylindracea lipase gene, which were used in an attempt to amplify Malassezia lipases, yielded an amplification product after annealing at 55 degrees C only with M. pachydermatis. This specific amplification may facilitate the rapid identification of this organism.

SUBMITTER: Gupta AK

PROVIDER: S-EPMC86611 | biostudies-literature | 2000 May

REPOSITORIES: biostudies-literature

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Molecular differentiation of seven Malassezia species.

Gupta A K AK Kohli Y Y Summerbell R C RC

Journal of clinical microbiology 20000501 5

A system based on PCR and restriction endonuclease analysis was developed to distinguish the seven currently recognized Malassezia species. Seventy-eight strains, including authentic culture collection strains and routine clinical isolates, were investigated for variation in the ribosomal DNA repeat units. Two genomic regions, namely, the large subunit of the ribosomal gene and the internal transcribed spacer (ITS) region, were amplified by PCR, and products were digested with restriction endonu ...[more]

PMID: 10790115

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Project description:Continued reports of Middle East respiratory syndrome coronavirus (MERS-CoV) infecting humans have occurred since the identification of this virus in 2012. MERS-CoV is prone to cause endemic disease in the Middle East, with several dozen spillover infections to other continents. It is hypothesized that MERS-CoV originated from bat coronaviruses and that dromedary camels are its natural reservoir. Although gene segments identical to MERS-CoV were sequenced from certain species of bats and one species experimentally shed the virus, it is still unknown whether other bats can transmit the virus. Here, at the molecular level, we found that all purified bat CD26s (bCD26s) from a diverse range of species interact with the receptor binding domain (RBD) of MERS-CoV, with equilibrium dissociation constant values ranging from several to hundreds at the micromolar level. Moreover, all bCD26s expressed in this study mediated the entry of pseudotyped MERS-CoV to receptor-expressing cells, indicating the broad potential engagement of bCD26s as MERS-CoV receptors. Further structural analysis indicated that in the bat receptor, compared to the human receptor, substitutions of key residues and their adjacent amino acids leads to decreased binding affinity to the MERS-RBD. These results add more evidence to the existing belief that bats are the original source of MERS-CoV and suggest that bCD26s in many species can mediate the entry of the virus, which has significant implications for the surveillance and control of MERS-CoV infection.IMPORTANCE In this study, we found that bat CD26s (bCD26s) from different species exhibit large diversities, especially in the region responsible for binding to the receptor binding domain (RBD) of Middle East respiratory syndrome coronavirus (MERS-CoV). However, they maintain the interaction with MERS-RBD at varied affinities and support the entry of pseudotyped MERS-CoV. These bat receptors polymorphisms seem to confer evolutionary pressure for the adaptation of CD26-binding virus, such as the ancestor of MERS-CoV, and led to the generation of diversified CD26-engaging CoV strains. Thus, our data add more evidence to support that bats are the reservoir of MERS-CoV and similar viruses, as well as further emphasize the necessity to survey MERS-CoV and other CoVs among bats.

Project description:BackgroundThe Malassezia yeasts which belong to the physiological microflora of human skin have also been implicated in several dermatological disorders, including pityriasis versicolor (PV), atopic dermatitis (AD), and psoriasis (PS). The Malassezia genus has repeatedly been revised and it now accommodates 14 species, all but one being lipid-dependent species. The traditional, phenotype-based identification schemes of Malassezia species are fraught with interpretative ambiguities and inconsistencies, and are thus increasingly being supplemented or replaced by DNA typing methods. The aim of this study was to explore the species composition of Malassezia microflora on the skin of healthy volunteers and patients with AD and PS.MethodsSpecies characterization was performed by conventional, culture-based methods and subsequently molecular techniques: PCR-RFLP and sequencing of the internal transcribed spacer (ITS) 1/2 regions and the D1/D2 domains of the 26S rRNA gene. The Chi-square test and Fisher's exact test were used for statistical analysis.ResultsMalassezia sympodialis was the predominant species, having been cultured from 29 (82.9%) skin samples collected from 17 out of 18 subjects under the study. Whereas AD patients yielded exclusively M. sympodialis isolates, M. furfur isolates were observed only in PS patients. The isolation of M. sympodialis was statistically more frequent among AD patients and healthy volunteers than among PS patients (P < 0.03). Whether this mirrors any predilection of particular Malassezia species for certain clinical conditions needs to be further evaluated. The overall concordance between phenotypic and molecular methods was quite high (65%), with the discordant results being rather due to the presence of multiple species in a single culture (co-colonization) than true misidentification. All Malassezia isolates were susceptible to cyclopiroxolamine and azole drugs, with M. furfur isolates being somewhat more drug tolerant than other Malassezia species.ConclusionsThis study provides an important insight into the species composition of Malassezia microbiota in human skin. The predominance of M. sympodialis in both normal and pathologic skin, contrasts with other European countries, reporting M. globosa and M. restricta as the most frequently isolated Malassezia species.

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Molecular differentiation of seven Malassezia species.

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Molecular differentiation of seven Malassezia species.

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