Cyptococcus neoformans und Guizotia abyssinica (syn. G. oleifera D. C.)

Staib, F.

doi:10.1007/bf02156784

Cited by 117 publications

(48 citation statements)

References 5 publications

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“…The synthesis of melanin in fungi by the DOPA-melanin pathway, also known as eumelanin, requires the presence of exogenous substrate in the form of certain o-diphenolic and p-diphenolic compounds, such as 3,4 dihydroxyphenylalanine (L-DOPA) [11]. The pathogenic fungi investigated in the production of DOPA-melanins via polyphenoloxidase (a laccase) include many model organisms such as Cryptococcus neoformans [12,13], Paracoccidioides brasiliensis [14,15], Histoplasma capsulatum [16], Blastomyces dermatitidis [17], Candida albicans [18], and Coccidioides posadasii [19].…”

Section: Introductionmentioning

confidence: 99%

Melanin as a virulence factor of Paracoccidioides brasiliensis and other dimorphic pathogenic fungi: a minireview

et al. 2008

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Melanin pigments are substances produced by a broad variety of pathogenic microorganisms, including bacteria, fungi, and helminths. Microbes predominantly produce melanin pigment via tyrosinases, laccases, catecholases, and the polyketide synthase pathway. In fungi, melanin is deposited in the cell wall and cytoplasm, and melanin particles (''ghosts'') can be isolated from these fungi that have the same size and shape of the original cells. Melanin has been reported in several human pathogenic dimorphic fungi including Paracoccidioides brasiliensis, Sporothrix schenckii, Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides posadasii. Melanization appears to contribute to virulence by reducing the susceptibility of melanized fungi to host defense mechanisms and antifungal drugs.

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Section: Introductionmentioning

confidence: 99%

Melanin as a virulence factor of Paracoccidioides brasiliensis and other dimorphic pathogenic fungi: a minireview

et al. 2008

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“…More than 35 years ago, Staib first described in vitro melanin pigmentation by C. neoformans and associated the phenomenon with virulence (31). In spite of considerable efforts by several investigators, many aspects of the nature of laccasederived products in vivo remain unclear.…”

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confidence: 99%

Laccase of Cryptococcus neoformans Is a Cell Wall-Associated Virulence Factor

et al. 2001

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Virulence is the outcome of an interaction between the host and a microbe and is characterized by a large array of opposing reactions operating at the host-pathogen interface. Cryptococcus neoformans is an important opportunistic pathogen in immunocompromised patients, including those with human immunodeficiency virus, and expresses a virulence-associated laccase which is believed to oxidize brain catecholamines and iron as a defense against host immune cells. In the present report, we investigated the cellular location of laccase to understand more fully how it contributes to cryptococcal virulence. A monoclonal antibody to the C. neoformans laccase was generated and used to show localization in the cell walls of representative serotype A (H99) and serotype D (B-3501) strains by immunoelectron microscopy. In addition, confocal microscopy was used to show a peripheral location of green fluorescent protein-tagged laccase expressed in live H99 cells. Biochemical studies showed that laccase could be released from intact cells or cell wall fractions with glucanase enzymes but was retained in the cell wall after sequential extraction with 1 M NaCl, 6 M urea, and 1% sodium dodecyl sulfate. The presence of a hydrolyzable bond linking laccase to the cell wall was suggested by removal of laccase from cell wall preparations after they were boiled in 1% sodium dodecyl sulfate, as was the presence of a disulfide or thioester bond by removal with dithiothreitol or ␤-mercaptoethanol. These data show that laccase is present as a tightly associated cell wall enzyme that is readily accessible for interactions with host immune cells.

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“…In general, colonies of different strains are difficult to distinguish on Sabouraud dextrose agar (SDA), which is used as a primary plating medium by most mycological laboratories. During previous experiments (16), it was observed that C. neoformans isolated from the nasopharynx of AIDS patients exhibited differences in colony morphology when grown on Niger seed agar (NSA) (15). The presence of Guizotia abyssinica in this medium induces the production of melanin by C. neoformans, resulting in distinctive brown colonies.…”

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Phenotypic Switching and Genetic Diversity of Cryptococcus neoformans

et al. 2001

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Niger seed agar was used as a primary plating medium for the isolation of Cryptococcus neoformans from cerebrospinal fluid specimens from AIDS patients with untreated primary cryptococcosis. The medium was used as the primary means to detect variations in the colony morphology of the yeast. To search for phenotypic and genetic variations, nine patients individually harboring two or three types of colony morphology were studied. Intraindividual isolates from nine patients had minor variations in the API 20C profile, and the MICs of one or more antifungal agents (amphotericin B, fluconazole, and itraconazole) for isolates from three patients were significantly different. Intraindividual isolates from three patients had minor karyotype differences, and one showed a dramatic chromosomal length polymorphism. In addition, three serial isolates from a patient with two episodes of infection showed similar karyotypes, confirming persistent infection by the same strain. Random amplified polymorphic DNA products were identical for all isolates (including three isolates from a relapse case). Our results provided evidence suggesting that (i) in humans, C. neoformans may undergo phenotypic and genetic changes during early infection prior to antifungal agent administration; (ii) dramatic variations in electrophoretic karyotypes and in phenotypes, as demonstrated during the early infection of one patient, may be due to infection by different strains; and (iii) the use of niger seed agar as a primary plating medium is useful for studying antifungal susceptibility, phenotypic switching, genetic diversity, and multiplestrain infections.

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Cyptococcus neoformans und Guizotia abyssinica (syn. G. oleifera D. C.)

Cited by 117 publications

References 5 publications

Melanin as a virulence factor of Paracoccidioides brasiliensis and other dimorphic pathogenic fungi: a minireview

Melanin as a virulence factor of Paracoccidioides brasiliensis and other dimorphic pathogenic fungi: a minireview

Laccase of Cryptococcus neoformans Is a Cell Wall-Associated Virulence Factor

Phenotypic Switching and Genetic Diversity of Cryptococcus neoformans

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