Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cryptococcus neoformans”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMed2004

Serotype and PCR-fingerprints of clinical and environmental isolates of Cryptococcus neoformans in Chiang Mai, Thailand.

From May 1999 to April 2000, serotypes of clinical and environmental isolates of Cryptococcus neoformans were studied in Chiang Mai province, northern Thailand. Three hundred and eighty-five environmental samples, of which 100 were dove droppings, 55 pigeon droppings and 230 eucalyptus flower, were collected from 7 Amphoes in Chiang Mai. C. neoformans was isolated from 45 of 100 (45.0%) dove dropping samples, 9 of 55 (16.4%) pigeon dropping samples and 2 of 230 (0.9%) eucalyptus flower samples. Serotypes of 56 environmental isolates and 75 clinical isolates of C. neoformans,obtained during the same period, were determined by the slide agglutination test. Fifty-six environmental and 74 clinical isolates belonged to C. neoformans serotype A (C. neoformans var. grubii), and only one clinical isolate belonged to C. neoformans serotype AD. The isolation of C. neoformans var. grubii from eucalyptus flower samples suggests contamination of avian droppings. PCR-fingerprinting, using (GACA)4 as a primer, discriminated 131 clinical and environmental isolates into 2 groups (group I and II). Seventy-five clinical and 54 environmental isolates were of group I, which had two major specific bands of approximately 1,250 and 960 base pairs. Two environmental isolates, one from pigeon excreta and the other from a eucalyptus flower sample were of group II, which had two major specific bands of approximately 1,180 and 500 base pairs.

Animals↗
PubMed2000

Susceptibility of Cryptococcus neoformans by the NCCLS microdilution and Etest methods using five defined media.

The susceptibility of 12 isolates of Cryptococcus neoformans to amphotericin B, 5-fluorocytosine, fluconazole, itraconazole and ketoconazole was tested using the NCCLS and Etest methods with yeast nitrogen base (YNB) pH 5.6 and pH 7.0, RPMI MOPS pH 7.0 with and without added glucose (2%) and RPMI buffered with phosphate buffer to pH 7.0. Some isolates yielded poor growth in RPMI MOPS after 72 h. Tests indicated that YNB pH 5.6 was the best medium for 5-fluorocytosine but was unsuitable for ketoconazole. In conclusion, YNB pH 7.0 or RPMI MOPS with 2% glucose can be used with either method.

Amphotericin B↗
PubMed1975

Factors affecting experimental infection with Cryptococcus neoformans in mice with special reference to an endotoxic substance of C. neoformans.

A close correlation was observed between body weight and length of the survival time of mice inoculated intravenously (i.v.) with Cryptococcus neoformans (p less than 0.001). An endotoxic substance of C. neoformans (Cr-ET) increased the susceptibility of mice to i.v. infection of C. neoformans only when more than 50 mug of Cr-ET was injected i.v. 24 hours before infection. Intraperitoneal (i.p.) administration of dimethyl sulfoxide which is found to enhance bacterial infection did not enhance death rate of mice infected i.p. with C. neoformans.

Animals↗
PubMed2003

Mitochondria are inherited from the MATa parent in crosses of the basidiomycete fungus Cryptococcus neoformans.

Previous studies demonstrated that mitochondrial DNA (mtDNA) was uniparentally transmitted in laboratory crosses of the pathogenic yeast Cryptococcus neoformans. To begin understanding the mechanisms, this study examined the potential role of the mating-type locus on mtDNA inheritance in C. neoformans. Using existing isogenic strains (JEC20 and JEC21) that differed only at the mating-type locus and a clinical strain (CDC46) that possessed a mitochondrial genotype different from JEC20 and JEC21, we constructed strains that differed only in mating type and mitochondrial genotype. These strains were then crossed to produce hyphae and sexual spores. Among the 206 single spores analyzed from six crosses, all but one inherited mtDNA from the MATa parents. Analyses of mating-type alleles and mtDNA genotypes of natural hybrids from clinical and natural samples were consistent with the hypothesis that mtDNA is inherited from the MATa parent in C. neoformans. To distinguish two potential mechanisms, we obtained a pair of isogenic strains with different mating-type alleles, mtDNA types, and auxotrophic markers. Diploid cells from mating between these two strains were selected and 29 independent colonies were genotyped. These cells did not go through the hyphal stage or the meiotic process. All 29 colonies contained mtDNA from the MATa parent. Because no filamentation, meiosis, or spore formation was involved in generating these diploid cells, our results suggest a selective elimination of mtDNA from the MATalpha parent soon after mating. To our knowledge, this is the first demonstration that mating type controls mtDNA inheritance in fungi.

Crosses, Genetic↗
PubMed1994

Differentiation of Cryptococcus neoformans serotypes A and D using creatinine dextrose bromothymol blue thymine medium.

A serotype differentiation of the encapsulated yeast Cryptococcus neoformans is described using creatinine dextrose bromothymol blue thymine (CDBT) medium. On CDBT medium C. neoformans serotype D grew as bright red colonies, turning the medium a bright orange after five days incubation at 28 degrees C. C. neoformans serotype A grew as pale colonies with no apparent colour effect on the medium. Serotypes B and C caused a slight greening of the medium. The reaction of the four serotypes of C. neoformans on CDBT medium is considered useful in the differentiation of the closely related serotype A and D.

Bromthymol Blue↗
PubMed1995

Sterol compositions and susceptibilities to amphotericin B of environmental Cryptococcus neoformans isolates are changed by murine passage.

Previous studies have shown that sequential isolates from patients with persistent Cryptococcus neoformans meningoencephalitis can vary in sterol composition and susceptibility to antifungal drugs. To investigate the potential of host factors as mediators of this phenomenon, we compared fungal susceptibilities of environmental and clinical isolates from a limited geographic area. Clinical isolates were less susceptible to amphotericin B than environmental isolates. Five environmental isolates were passaged through BALB/c murine hosts; the passaged isolates had changes in sterol composition and reduced amphotericin B susceptibilities relative to those of the parent isolates. In contrast, murine passage of these isolates did not alter their susceptibilities to fluconazole. The results confirm that changes in sterol composition and antifungal susceptibility can occur in vivo as a result of host factors and suggest that human infection can result in selection of variants with reduced susceptibilities to amphotericin B.

Amphotericin B↗
PubMed2005

In vitro susceptibility of Cryptococcus neoformans clinical isolates from Egypt to seven antifungal drugs.

The in vitro susceptibility of 29 clinical isolates of Cryptococcus neoformans to fluconazole, miconazole, itraconazole, ketoconazole, flucytosine, nystatin and amphotericin B was tested by broth and colorimetric microdilution methods. Most of the isolates showed uniform patterns of susceptibility to the used antifungal agents. Only three isolates exhibited resistance [fourfold or greater rise in the minimum inhibitory concentrations (MICs)] to the tested antifungal drugs. The MIC50 and MIC90 were 0.5-8 mg l(-1) for 5-flucytosine, 0.2-8.25 mg l(-1) for nystatin, 0.5-16 mg l(-1) for fluconazole and 0.2-12.5 mg l(-1) for miconazole. However, MIC50 and MIC90 were in narrow range for the clinical yeast isolates in both methods used and showed 0.5-1 mg l(-1) for amphotericin B and 0.016-0.25 mg l(-1) for both ketoconazole and itraconazole. The combination of fluconazole plus flucytosine showed greater synergistic and fungicidal activity compared with that of fluconazole plus amphotericin B or the use of individual drugs.

Antifungal Agents↗
PubMed2002

Mitochondrial DNA polymorphisms in the human pathogenic fungus Cryptococcus neoformans.

This study examined mitochondrial DNA (mtDNA) restriction site polymorphisms among 416 strains of the human pathogenic yeast Cryptococcus neoformans from the United States and Japan. The strains included 378 serotype A, 14 serotype D, 18 serotype AD, two serotype B, and two strains whose serotype could not be determined using current commercial monoclonal antibodies. Portions of two genes were examined: (1) the mitochondrial large ribosomal RNA gene (mtLrRNA) and (2) the NADH dehydrogenase subunit 2 ( ND2). To screen for polymorphisms among the 416 strains, the endonuclease MaeIII was used to digest the PCR-amplified mtLrRNA gene fragment and three endonucleases ( BanI, AluI, MseI) were used to digest the PCR-amplified ND2 gene fragment. Four mtDNA haplotypes were identified among these strains. All strains of serotype A had mtDNA haplotype I, strains of serotype D had haplotype II, and strains of serotype B had haplotypes III and IV. Of the two non-typable strains, one was haplotype I while the other was haplotype II. Among the strains of serotype AD, 14 were haplotype I and the other four were haplotype II. These results were discussed in the context of recent findings regarding the origins of serotype AD strains and the observed uniparental mtDNA inheritance in laboratory crosses between strains of serotypes A and D.

Cryptococcus neoformans↗
PubMed1971

Pigment production of Cryptococcus neoformans grown with extracts of Guizotia abyssinica.

Brown pigment(s) formed in Cryptococcus neoformans when grown on media containing extracts of the seeds of Guizotia abyssinica cannot be extracted by common organic solvents or by 6 n HCl or 2 n NaOH. A similar pigmentation was observed in C. neoformans when grown on a medium containing caffeic acid isolated from the hydrolyzed methanol extract of G. abyssinica seeds. Its methyl ester and the diacetate thereof, as well as the following structurally related compounds, 3-hydroxytyramine, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylethanolamine, and 4-hydroxy-3,5-dimethoxycinnamic acid, brought about similar pigmentation. However, 2,4-, 2,5-, 2,6-, and 3,5-dihydroxybenzoic acids, tyrosine, phenylalanine, cinnamic acid, 4-hydroxycinnamic acid, and 4-hydroxy-3-methoxycinnamic acid did not cause coloration in C. neoformans.

Cinnamates↗
PubMed2000

Environmental isolation of Cryptococcus neoformans var. gattii and C. neoformans var. neoformans in the city of São Paulo, Brazil.

In order to determine the environmental occurrence of both varieties of Cryptococcus neoformans in the city of São Paulo, pigeon droppings and vegetable material from trees of the genus Eucalyptus were collected at typically crowded places. A total of 38 sites downtown where large heaps of pigeon droppings could be found were selected for sampling. Pigeon droppings from 10 (26.3%) of these sites were positive for C. neoformans var. neoformans in at least one sample. Twelve eucalyptus woods located within four municipal parks were also surveyed; vegetable material from Eucalyptus spp. trees were collected monthly over a 2-year period. C. neoformans var. gattii was recovered from a wood in Ibirapuera Park during the same season on two different occasions (November 1996 and November 1997); this park contained specimens of Eucalyptus camaldulensis, a natural habitat of C. n. var. gattii. C. n. var. neoformans was detected in a wood in Ibirapuera Park and Aclimação Park. The results show that both C. n. var. neoformans and C. n. var. gattii are present in the urban environment of São Paulo city at sites where large numbers of people normally gather.

Animals↗
PubMed1995

Antibodies to Cryptococcus neoformans glucuronoxylomannan enhance antifungal activity of murine macrophages.

Monoclonal antibodies (MAbs) to the capsular polysaccharide of the pathogenic fungus Cryptococcus neoformans can prolong survival and decrease organ fungal burden in experimental murine cryptococcosis. To investigate the mechanism of antibody-mediated protection, the interaction of C. neoformans and murine macrophage-like J774.16 cells was studied in the presence and absence of MAbs differing in isotype. Immunoglobulin G2a (IgG2a) and IgG2b isotype switch variants were isolated from an IgM hybridoma to complete the IgG subclass set. IgM, IgG1, IgG2a, IgG2b, IgG3, and IgA MAbs were studied for their ability to promote phagocytosis and reduce the number of CFU in C. neoformans and J774.16 cell cocultures. The MAbs in this set had similar if not identical fine specificities and were derived from a single B cell. All isotypes promoted phagocytosis; however, the IgG subclasses were more effective opsonins than IgM or IgA. All isotypes enhanced J774.16 anti-C. neoformans activity in vitro, as measured by a reduction in the number of CFU. The IgG1 MAbs were consistently more active in promoting opsonization and reducing the number of CFU. Addition of IgG1 MAb to C. neoformans and J774.16 cocultures resulted in rapid reduction in the number of CFU, which is consistent with fungal killing. Electron microscopy revealed that MAb-opsonized C. neoformans cells were internalized and appeared damaged. Administration of IgM, IgG1, IgG2a, and IgG2b isotype switch variant MAbs revealed that the IgG2a and IgG2b subclasses were the most and least effective isotypes, respectively, in prolonging survival in an intraperitoneal murine infection model. The results indicate that murine antibody subclasses differ in their ability to enhance macrophage anti-C. neoformans activity and suggest that antibody enhancement of macrophage function is a mechanism by which antibodies modify infection in vivo.

Animals↗
PubMed1996

Oxidative killing of Cryptococcus neoformans by human neutrophils. Evidence that fungal mannitol protects by scavenging reactive oxygen intermediates.

Polymorphonuclear neutrophils (PMN) kill Cryptococcus neoformans (Cn) by oxidative mechanisms, but the roles of various reactive oxygen intermediates (ROIs) are not known. We used a mannitol low-producing Cn mutant (Cn MLP) and its wild-type parent (Cn H99) to examine the role of ROIs distal to H2O2 in PMN killing and to determine whether mannitol produced by Cn protects the fungus against ROIs. At PMN:Cn cell ratios of 1:1, 10:1, and 100:1, PMN killed significantly more Cn MLP than Cn H99 cells after 2 and 4 h (p less than 0.05). Superoxide dismutase and the hydroxyl radical (OH.) scavengers mannitol and DMSO inhibited killing of both strains (p less than 0.05), but catalase did not. Cn H99 and Cn MLP stimulated PMN to produce similar amounts of O2- and H2O2. In contrast, Cn MLP stimulated greater luminol-dependent chemiluminescence than did Cn H99 (p less than 0.05). Finally, H2O2 alone killed similar numbers of Cn H99 and Cn MLP cells, but oxidants generated by FeSO4 (1 microM), H2O2 (10 microM), and iodide (1 to 3 microM) killed significantly more Cn MLP than Cn H99 cells in 1 h (p less than 0.05). Mannitol, DMSO, and catalase completely inhibited killing of both Cn strains by this cellfree system, but superoxide dismutase did not. These results suggest that 1) distal ROIs such as OH. and HOCI are key effector molecules against Cn, and 2) mannitol produced by Cn may protect against oxidative killing by scavenging distal ROIs.

Cell-Free System↗
PubMed2004

Cryptococcus neoformans CAP59 (or Cap59p) is involved in the extracellular trafficking of capsular glucuronoxylomannan.

Several genes are essential for Cryptococcus neoformans capsule synthesis, but their functions are unknown. We examined the localization of glucuronoxylomannan (GXM) in strain B-3501 and in cap59 mutants B-4131 and C536. Wild-type strain B-3501 showed a visible capsule by India ink staining and immunofluorescence with anticapsular monoclonal antibodies (MAbs) 12A1 and 18B7. B-4131, a mutant containing a missense mutation in CAP59, showed no capsule by India ink staining but revealed the presence of capsular polysaccharide on the cell surface by immunofluorescence. The cap59 gene deletion mutant (C536), however, did not show a capsule by either India ink staining or immunofluorescence. Analysis of cell lysates for GXM by enzyme-linked immunosorbent assay revealed GXM in C536 samples. Furthermore, the epitopes recognized by MAbs 12A1, 2D10, 13F1, and 18B7 were each detected in the cytoplasm of all strains by immunogold electron microscopy, although there were differences in location consistent with differences in epitope synthesis and/or transport. In addition, the cells of B-3501 and B-4131, but not those of the cap59 deletant, assimilated raffinose or urea. Hence, the missense mutation of CAP59 in B-4131 partially hampered the trafficking of GXM but allowed the secretion of enzymes involved in hydrolysis of raffinose or urea. Furthermore, the cell diameter and volume for strain C536 are higher than those for strain B-3501 or B-4131 and may suggest the accumulation of cellular material in the cytoplasm. Our results suggest that CAP59 is involved in capsule synthesis by participating in the process of GXM (polysaccharide) export.

Biological Transport↗
PubMed2005

Comparative analysis of pathogenicity of Cryptococcus neoformans serotypes A, D and AD in murine cryptococcosis.

OBJECTIVES: To characterize the pathogenicity of 15 strains of Cryptococcus neoformans belonging to several serotype/mating type allele patterns (Dalpha, Da, A(alpha), A(a), A(alpha)/D(a) and D(alpha)/A(a)) in experimental models of murine cryptococcosis. METHODS: CD1-infected mice were examined for survival and fungal loads in either brain or lung during the course of infection. RESULTS: All strains, with the exception of one Da strain, produced melanin in vitro. Similarly, all strains were encapsulated and produced phospholipase. When CD1 mice were challenged intravenously (i.v.) with 5x10(5)CFU/mouse and observed for 60 days post-infection, a significant variation of mortality rate was observed among mice infected with different strains. A(alpha) and A(alpha)/D(a) strains all produced 100% mortality within the study period with mean survivals significantly shorter than those of mice infected with strains belonging to any other allele type (P<0.0001). A wide range of pathogenicity was shown by haploid and diploid strains presenting D(alpha) allele. This finding was confirmed by an intranasal model of challenge. To investigate the progression of infection, the mice were challenged i.v. with 5x10(4)CFU/mouse and tissue burden experiments (brain and lung) were performed on days 6 and 12 post-infection. Only the mice infected with A(alpha) and A(alpha)/D(a) strains showed a >1 log(10) increase of CFU/g in both tissues throughout the study period. CONCLUSIONS: Our results suggest that the presence of the A(alpha) mating type allele in either haploid or diploid strains is correlated with virulence, while the presence of the A(a) or D(a) allele in haploid strains is associated with moderate or no virulence. Finally, either haploid or diploid strains presenting D(alpha) allele vary in virulence.

Animals↗
PubMed2000

Direct PCR of Cryptococcus neoformans MATalpha and MATa pheromones to determine mating type, ploidy, and variety: a tool for epidemiological and molecular pathogenesis studies.

Cryptococcus neoformans MATalpha and MATa pheromones were amplified by direct PCR. Nucleotide sequence analyses revealed unique restriction enzyme sites. Sixty strains were used to devise a restriction fragment length polymorphism typing scheme that yielded three variety-specific patterns. Additionally, pheromone-specific PCR allowed easier identification of diploid C. neoformans strains than flow cytometry.

Cryptococcosis↗
PubMed1997

Inhibition of swine microglial cell phagocytosis of Cryptococcus neoformans by femtomolar concentrations of morphine.

Microglia are important immune effector cells within the brain. The phagocytosis of nonopsonized Cryptococcus neoformans by swine microglia was used as an in vitro model for studies on cellular mechanisms of opiate-mediated immunomodulation in the brain. Morphine inhibited potently (IC50 approximately 10(-16) M) the phagocytosis of C. neoformans by primary cultures of neonatal pig microglia. The mu opioid agonist Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol (DAMGO) also suppressed phagocytosis but with a much lower potency than morphine (IC50 approximately 10(-8) M). The inhibitory effects of morphine and DAMGO were blocked by equimolar concentrations of naloxone and by the selective mu opiate receptor antagonist beta-funaltrexamine. Pertussis toxin but not cholera toxin reversed the inhibitory effects of both morphine and DAMGO. Our data suggest that morphine inhibits phagocytosis of C. neoformans by swine microglia via a mechanism involving mu opiate receptors coupled to a pertussis toxin-sensitive Gi/G(o) protein signaling pathway.

Animals↗
PubMed1985

A Cryptococcus neoformans strain from the brain of a wildlife fox (Vulpes vulpes) suspected of rabies: mycological observations and comments.

A Cryptococcus neoformans strain which in 1983 caused an infection of the central nervous system (CNS) in a wildlife fox with rabies-like symptoms was tested for its strain-specific brown colour effect (BCE) on Guizotia abyssinica creatinine agar and for its ability to assimilate creatinine. Both reactions were found to be positive. These results were found to be largely identical with those of 2 out of 3 strains having caused fatal cryptococcosis in 1970, 1979 and 1983 in persons living in the area where the fox had been found (radius 40-100 km). Some theoretical aspects of the epidemiology and pathogenesis of cryptococcosis in the wildlife fox and rodents are discussed. For further epidemiological investigations into the prevalence of Cr. neoformans in man and animals in this area, the two reactions for detecting and typing, i.e. the BCE on Guizotia abyssinica creatinine agar and the creatinine assimilation are proposed.

Animals↗
PubMed2001

Both Th1 and Th2 cytokines affect the ability of monoclonal antibodies to protect mice against Cryptococcus neoformans.

Variable-region-identical mouse immunoglobulin G1 (IgG1), IgG2b, and IgG2a monoclonal antibodies to the capsular polysaccharide of Cryptococcus neoformans prolong the lives of mice infected with this fungus, while IgG3 is either not protective or enhances infection. CD4+ T cells are required for IgG1-mediated protection, and CD8+ T cells are required for IgG3-mediated enhancement. Gamma interferon is required for both effects. These findings revealed that T cells and cytokines play a role in the modulation of cryptococcal infection by antibodies and suggested that it was important to more fully define the cytokine requirements of each of the antibody isotypes. We therefore investigated the efficacy of passively administered variable-region-identical IgG1, IgG2a, IgG2b, and IgG3 monoclonal antibodies against intravenous infection with C. neoformans in mice genetically deficient in interleukin-12 (IL-12), IL-6, IL-4, or IL-10, as well as in the parental C57BL/6J strain. The relative inherent susceptibilities of these mouse strains to C. neoformans were as follows: IL-12(-/-) > IL-6(-/-) > C57BL/6J approximately IL-4(-/-) >> IL-10(-/-). This is consistent with the notion that a Th1 response is necessary for natural immunity against cryptococcal infection. However, none of the IgG isotypes prolonged survival in IL-12(-/-), IL-6(-/-), or IL-4(-/-) mice, and all isotypes significantly enhanced infection in IL-10(-/-) mice. These results indicate that passive antibody-mediated protection against C. neoformans requires both Th1- and Th2-associated cytokines and reveal the complexity of the mechanisms through which antibodies modulate infection with this organism.

Animals↗