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PubMed1993

Fluconazole-resistant Cryptococcus neoformans var gattii in an AIDS patient.

We describe a case of meningitis due to Cryptococcus neoformans var gattii in an AIDS patient. The reasons for the observed predominance of C. neoformans var neoformans infections in AIDS patients living in areas endemic for the gattii variety are not understood thus far. Treatment with fluconazole resulted in poor clinical and mycological response. In vitro sensitivity testing of the fungus revealed high minimal inhibitory concentrations, suggesting fluconazole resistance. Treatment with amphotericin B was successful.

AIDS-Related Opportunistic Infections↗
PubMed2002

Cell identity and sexual development in Cryptococcus neoformans are controlled by the mating-type-specific homeodomain protein Sxi1alpha.

Virulence in the human fungal pathogen Cryptococcus neoformans is associated with the alpha mating type. Studies to identify the properties of alpha cells that enhance pathogenesis have led to the identification of a mating-type locus of unusually large size and distinct architecture. Here, we demonstrate that the previously identified MATalpha components are insufficient to regulate sexual differentiation, and we identify a novel alpha-specific regulator, SXI1alpha. Our data show that SXI1alpha establishes alpha cell identity and controls progression through the sexual cycle, and we discover that ectopic expression of SXI1alpha in a cells is sufficient to drive a/alpha sexual development. SXI1alpha is the first example of a key regulator of cell identity and sexual differentiation in C. neoformans, and its identification and characterization lead to a new model of how cell fate and the sexual cycle are controlled in C. neoformans.

Cryptococcus neoformans↗
PubMed1998

Simultaneous infection with Blastomyces dermatitidis and Cryptococcus neoformans.

In this report, we present two cases of simultaneous infection with Blastomyces dermatitidis and Cryptococcus neoformans. In both cases, fungi were isolated from the lungs. The clinical manifestations were not suggestive of infection with two fungi. One patient was receiving immunosuppressive therapy and another was otherwise immunocompetent. A review of the literature failed to uncover any reports of co-infection with these two fungal pathogens. We discuss possible mechanisms for the isolation of both pathogens.

Aged↗
PubMed2001

Capsular reactions of Cryptococcus neoformans with polyspecific and oligospecific polyclonal anticapsular antibodies.

Monoclonal antibodies to the capsular polysaccharide of Cryptococcus neoformans produce distinct capsular reactions and have biological activities that are determined by serotype specificity. In the present study, polyclonal rabbit anticapsular antibodies were cross-absorbed to produce serotype specificities similar to those of monoclonal antibodies. The results showed that polyclonal and monoclonal antibodies with similar serotype specificities have similar capsular reactions and biological activities.

Animals↗
PubMed1995

Cross-resistance to polyene and azole drugs in Cryptococcus neoformans.

Fluconazole was observed to inhibit sterol 14 alpha-demethylase in the human pathogen Cryptococcus neoformans, and accumulation of a ketosteroid product was associated with growth arrest. A novel mechanism(s) of azole and amphotericin B cross-resistance was identified, unrelated to changes in sterol biosynthesis, as previously identified in Saccharomyces cerevisiae. Reduced cellular content of drug could account for the resistance phenotype, indicating the possible involvement of a mechanism similar to multidrug resistance observed in higher eukaryotes.

Amphotericin B↗
PubMed2004

Environmental isolation of Cryptococcus neoformans from an endemic region of HIV-associated cryptococcosis in Thailand.

We successfully isolated Cryptococcus neoformans from chicken faeces in suburban areas of Thailand. C. neoformans was isolated from 36/150 houses (24.0%) in the dry season and 6/150 (4.0%) in the rainy season. All environmental isolates were of serotype A. The high isolation rate of 24% from chicken faeces has never been reported previously. Our environmental study could probably explain the high incidence of cryptococcal meningitis in HIV patients in Thailand.

Animals↗
PubMed2006

CPS1, a homolog of the Streptococcus pneumoniae type 3 polysaccharide synthase gene, is important for the pathobiology of Cryptococcus neoformans.

The polysaccharide capsule is known to be the major factor required for the virulence of Cryptococcus neoformans. We have cloned and characterized a gene, designated CPS1, that encodes a protein containing a glycosyltransferase moiety and shares similarity with the type 3 polysaccharide synthase encoded by the cap3B gene of Streptococcus pneumoniae. Cps1p also shares similarity with hyaluronan synthase of higher eukaryotes. Deletion of the CPS1 gene from a serotype D strain of C. neoformans resulted in a slight reduction of the capsule size as observed by using an India ink preparation. The growth at 37 degrees C was impaired, and the ability to associate with human brain endothelial cells in vitro was also significantly reduced by the deletion of CPS1. Using site-specific mutagenesis, we showed that the conserved glycosyltransferase domains are critical for the ability of the strain to grow at elevated temperatures. A hyaluronan enzyme-linked immunosorbent assay method demonstrated that CPS1 is important for the synthesis of hyaluronan or its related polysaccharides in C. neoformans. Comparisons between the wild-type and the cps1Delta strains, using three different transmission electron microscopic methods, indicated that the CPS1 gene product is involved in the composition or maintenance of an electron-dense layer between the outer cell wall and the capsule. These and the virulence studies in a mouse model suggested that the CPS1 gene is important in the pathobiology of C. neoformans.

Animals↗
PubMed2001

Phenotypic switching and genetic diversity of Cryptococcus neoformans.

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 multiple-strain infections.

AIDS-Related Opportunistic Infections↗
PubMed1998

In-vitro susceptibility of Cryptococcus neoformans isolates to fluconazole and itraconazole.

The in-vitro susceptibilities of 143 isolates of Cryptococcus neoformans, collected from British patients between 1994 and 1996, to fluconazole and itraconazole were compared with those of 36 isolates collected between 1971 and 1985, 41 isolates collected between 1986 and 1989, and 43 Ugandan isolates collected in 1996. Testing was done with a broth microdilution method in YNB medium supplemented with glucose, incubation at 30 degrees C for 72 h, and an endpoint of 50% inhibition. The results showed that the MIC ranges, MIC50s and MIC90s of fluconazole and itraconazole for C. neoformans isolates from the UK have remained unchanged despite the recent widespread use of triazoles for long-term maintenance of patients with AIDS-associated cryptococcal meningitis. The MIC ranges, MIC50s and MIC90s of the 43 isolates from untreated Ugandan patients with AIDS were similar to those of the British isolates. Examination of our records for 1994-96 revealed six cases in which a four-fold or greater rise in the MIC of fluconazole was associated with relapsed cryptococcal meningitis.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Binding of unopsonized Cryptococcus neoformans by human bronchoalveolar macrophages: inhibition by a large-molecular-size serum component.

Infection with Cryptococcus neoformans usually begins after inhalation of airborne organisms. Since levels of opsonins in the alveolar space may be low, the ability of human bronchoalveolar macrophages to bind C. neoformans in the presence and absence of opsonins was studied. Bronchoalveolar macrophages bound unopsonized C. neoformans. Surprisingly, component(s) in pooled human serum (PHS) inhibited binding, as evidenced by 26% and 71% inhibition of binding when 20% PHS and heat-inactivated PHS (HI-PHS), respectively, were added to the system. Separation of PHS by molecular size revealed that the inhibitory component had an apparent molecular weight greater than 10(6) and was inhibitory at nanomolar concentrations. PHS stimulated and HI-PHS had no effect on binding of acapsular C. neoformans and zymosan particles to bronchoalveolar macrophages. These data demonstrate that bronchoalveolar macrophages can bind unopsonized, encapsulated C. neoformans, but that serum component(s) inhibits binding.

Bacterial Adhesion↗
PubMed1976

In vitro and in vivo activity of 2,4-diamino-6-(2-(3,4-dichlorophenyl)acetamido) quinazoline against Cryptococcus neoformans.

The minimum inhibitory concentration of quinazoline derivative was determined by the tube dilution method for Cryptococcus neoformans, strain 184. The effect of this chemical agent on macromolecular metabolism indicated an inhibition of incorporations of labeled precursors into RNA and protein of C. neoformans. A mouse model infection with C. neoformans was established. Following this, the animals were given ip or oral doses of different concentrations of the experimental drug. Infected mice responded to ip administration of the drug in that the percentage of surviving mice increased progressively with increasing drug dosage. The curing dose 50 (CD50) was determined, based on the isolation of C. neoformans from organs of animals during or at the termination of the experiments.

Antifungal Agents↗
PubMedDate not supplied

Susceptibility testing of Cryptococcus neoformans using the urea broth microdilution method.

An urea broth microdilution method to assay the susceptibility of Cryptococcus neoformans to antifungal drugs was newly developed. Using this method, urease activity of the fungus was measured instead of the viability by checking colony development. The urease activities were indicated by colour changes in optical density at 545 nm. The end point in this assay was considered as 99% inhibitory concentration. When we measured antifungal activities of the three drugs against 16 isolates of Cr. neoformans using this assay method, mean minimum-inhibitory concentrations (MICs) of fluconazole, itraconazole and terbinafine were 2.0 micrograms ml-1, 0.008 microgram ml-1 and 0.25 microgram ml-1 respectively. This assay method resulted in higher sensitivity in MICs of the three antifungal drugs than the broth microdilution method recommended by the Committee for Laboratory Standards of the Japanese Society for Medical Mycology. The results obtained using this assay method support the more effective evaluation of antifungal substances in susceptibility testing of Cr. neoformans.

Antifungal Agents↗
PubMed2003

Investigation in Central Italy of the possible association between Cryptococcus neoformans var. Gattii and Eucalyptus camaldulensis.

The authors present a worldwide review of isolations of Cryptococcus neoformans, var. neoformans and C. neoformans var. gattii from animals and vegetation, referring in particular to the already well-known association of the former variety with Eucalyptus camaldulensis. They then review the Italian situation relative to this association and their studies carried out in Central Italy: in Latina (Lazio), Pisa, Viareggio and Lake Massaciuccoli (Tuscany). From the 256 E. camaldulensis trees examined C. neoformans var. gattii was not isolated. An E. camaldulensis tree situated in the nature reserve on Lake Massaciuccoli proved to be positive for C. neoformans var. neoformans. This variety was isolated from the leaves, flowers, bark and the debris at the foot of the tree, suggesting that it had colonized the entire tree and that it was capable of developing not only on its usual habitat (bird guano, soil rich with guano) but also on Eucalyptus trees. The identity of the isolates was confirmed by their genomic profiles obtained by random amplification polymorphic DNA (RAPD) with the primer (GACA)4. The presence of a single genotype indicates a sole source of contamination, perhaps brought by a bird coming from a contaminated environment.

Cryptococcosis↗
PubMed2005

Human cryptococcosis: relationship of environmental and clinical strains of Cryptococcus neoformans var. neoformans from urban and rural areas.

Forty-five clinical and 55 environmental strains of Cryptococcus neoformans var. neoformans from São Paulo, Brazil, were tested for their susceptibilities to amphotericin B, fluconazole, itraconazole, and flucytosine by the broth microdilution method according to the National Committee of Clinical Laboratory Standards guidelines. Electrophoretic karyotypes analysis by counter-clamped homogeneous electrophoresis was used to compare their genetic relatedness. Molecular typing revealed three clinical profiles very similar to two environmental profiles and an identical environmental and clinical profile. The results showed that human cryptococcosis can be acquired from environmental strains, which had similar minimum inhibitory concentration values to clinical strains, for antifungal agents.

Animals↗
PubMed2000

Early induction of interleukin-12 by human monocytes exposed to Cryptococcus neoformans mannoproteins.

Interleukin-12 (IL-12) production by human monocytes stimulated with mannoproteins (MPs) of Cryptococcus neoformans was investigated. The results reported show that secreted or cell-associated MPs induce an early and significant production of IL-12. MPs show different capabilities to quantitatively affect IL-12 production; MP2, an 8. 2-kDa MP purified from the culture supernatant of C. neoformans, appears to be the most potent stimulator. Cytochalasin B inhibits both internalization and IL-12 induction by MP. In addition, a drastic reduction of IL-12 was observed when monocytes were cultured in the absence of normal human serum or treated with soluble mannan. Early production of IL-12 promotes early secretion of gamma interferon by T cells but does not influence the magnitude of the MP-induced lymphoproliferative response. Overall our results identify cryptococcal antigens responsible for rapid and potent induction of IL-12 in monocytes. MPs appear to regulate IL-12 secretion by internalization via the endocytic pathway and by interaction with monocyte receptors or serum factors.

Cryptococcus neoformans↗
PubMed2005

The cellular responses induced by the capsular polysaccharide of Cryptococcus neoformans differ depending on the presence or absence of specific protective antibodies.

The capsule of Cryptococcus neoformans, the principal virulence factor of this fungus, is composed primarily of polysaccharide. The predominant component of the polysaccharide capsule is glucuronoxylomannan (GXM), a compound with potent immunoregulatory properties. GXM is bound and internalized by natural immune cells affecting innate and subsequent adaptive immune response. The cellular pattern recognition receptors involved in GXM binding include toll-like receptor (TLR)4, CD14, TLR2, CD18, Fc gamma receptor II (FcgammaRPi). This multiple cross-linking leads to a suppressive outcome that is arrested and even reversed by protective antibodies to GXM. This review analyzes the immunosuppressive effects induced by capsular material, considering its pattern recognition receptors, and dissects the mechanism of monoclonal antibody shifting to immunoactivation.

Antibodies, Fungal↗