Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cryptococcus”

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 649 records · Page 36Linked to original sources
PubMed2000

Thermolabile xylanase of the Antarctic yeast Cryptococcus adeliae: production and properties.

Xylanase production by the Antarctic psychrophilic yeast Cryptococcus adeliae was increased 4.3 fold by optimizing the culture medium composition using statistical designs. The optimized medium containing 24.2 g l(-1) xylan and 10.2 g l(-1) yeast extract and having an initial pH of 7.5 yielded xylanase activity at 400 nkat (nanokatal) ml(-1) after 168-h shake culture at 4 degrees C. In addition, very little endoglucanase, beta-mannanase, beta-xylosidase, beta-glucosidase, alpha-L-arabinofuranosidase, and no filter paper cellulase activities were detected. Among 12 carbon sources tested, maximum xylanase activity was induced by xylan, followed by lignocelluloses such as steamed wheat straw and alkali-treated bagasse. The level of enzyme activity produced on other carbon sources appeared to be constitutive. Among the complex organic nitrogen sources tested, the xylanase activity was most enhanced by yeast extract, followed by soymeal, Pharmamedia (cotton seed protein), and Alburex (potato protein). A batch culture at 10 degrees C in a 5-1 fermenter (3.5-1 working volume) using the optimized medium gave 385 nkat at 111 h of cultivation. The crude xylanase showed optimal activity at pH 5.0-5.5 and good stability at pH 4-9 (21 h at 4 degrees C). Although the enzyme was maximally active at 45 degrees - 50 degrees C, it appeared very thermolabile, showing a half-life of 78 min at 35 degrees C. At 40 degrees - 50 degrees C, it lost 71%-95% activity within 5 min. This is the first report on the production as well as on the properties of thermolabile xylanase produced by an Antarctic yeast.

Antarctic Regions↗
PubMed2000

Xylanase from the psychrophilic yeast Cryptococcus adeliae.

A xylanase belonging to family 10 is produced by Cryptococcus adeliae, an Antarctic yeast that exhibits optimal growth at low temperature. The mature glycosylated xylanase secreted by C. adeliae is composed of 338 amino acid residues and 26 +/- 3 osidic residues, and shares 84% identity with its mesophilic counterpart from C. albidus. The xylanase from C. adeliae is less thermostable than its mesophilic homologue when the residual activities are compared, and this difference was confirmed by differential scanning calorimetry experiments. In the range 0 degrees-20 degrees C, the cold-adapted xylanase displays a lower activation energy and a higher catalytic efficiency. All these observations suggest a less compact, more flexible molecular structure. Analysis of computerized molecular models built up for both psychrophilic and mesophilic xylanases indicates that the adaptation to cold consists of discrete changes in the tridimensional structure: of 53 substitutions, 22 are presumably involved in the adaptation process. These changes lead mainly to a less compact hydrophobic packing, to the loss of one salt bridge, and to a destabilization of the macrodipoles of the helices.

Amino Acid Sequence↗
PubMed2004

In vitro activity of amphotericin B, fluconazole and voriconazole against 162 Cryptococcus neoformans isolates from Africa and Cambodia.

In order to determine the potential role that various antifungal agents might have in the management of cryptococcosis in tropical areas, the in vitro susceptibility of Cryptococcus neoformans isolates from Africa ( n=52) and Cambodia ( n=110) to three antifungal agents (amphotericin B, fluconazole and voriconazole) were compared using the E-test method. The results of this study (i) confirm the value of the E-test for testing the in vitro susceptibility of C. neoformans towards voriconazole; (ii) provide the first evidence demonstrating good activity of amphotericin B, fluconazole and voriconazole against Cambodian isolates; and (iii) show there are differences in susceptibility between African and Asian C. neoformans isolates, with Cambodian isolates appearing less susceptible to the agents tested but with amphotericin B maintaining good activity.

Africa↗
PubMed2000

In vitro susceptibility of environmental Cryptococcus neoformans variety neoformans isolates from Turkey to six antifungal agents, including SCH56592 and voriconazole.

The in vitro antifungal susceptibility of 27 environmental (pigeon droppings) isolates of Cryptococcus neoformans var. neoformans, isolated from throughout Turkey, to six antifungal agents (amphotericin B, flucytosine, fluconazole, voriconazole, itraconazole, and SCH56592) was studied. Voriconazole, itraconazole, and SCH56592 all showed comparable activity and were more active than the remaining three antifungal agents tested. Overall, SCH56592 was the most active agent (MIC90, 0.015 microg/ml, at both 48 and 72 h), followed by itraconazole (MIC90, 0.03 microg/ml, at both 48 and 72 h) and voriconazole (MIC90, 0.25 microg/ml, at both 48 and 72 h), respectively. Antifungal susceptibility data for environmental isolates may reflect patterns for the clinical isolates recovered from patients from the same geographic area.

Animals↗
PubMedDate not supplied

Differences in mitochondrial genome organization of Cryptococcus neoformans strains.

The organization of the mitochondrial genomes in two strains belonging in different varieties of Cryptococcus neoformans was analysed. Physical maps of the mtDNA of the IFM5844 (var. neoformans) and IFO410 (var. grubii) strains were constructed by using EcoRI and EcoRV restriction enzymes; functional maps were constructed by hybridization, cloning and sequencing. Most of the genes important in the mitochondrial function (ND1, ND2, ND3, ND4, ND4L, ND5, ND6, ATP6, ATP9, COX1, COX2 and COB) and protein synthesis (SsrRNA and LsrRNA) were localized. We did not find any differences between the strains in the order of these genes. However, they differed significantly in the sizes of the mtDNAs: 32.6 kb for IFM5844, and 24.1 kb for IFO410. This can be attributed to two large regions of the mtDNA. In these regions, differences were found in the numbers of introns in COX1 (no intron in var. grubii, 5 introns in var. neoformans), COB (1 intron in var. grubii, 2 introns in var. neoformans), LsrRNA (no intron in var. grubii, 2 introns in var. neoformans), and ND5 (no intron in var. grubii, 1 intron in var. neoformans) genes. In several introns of the COB and COX1 genes LAGLIDADG motifs were found. Differences were also observed in the nucleotide sequences of some genes and in the sizes and sequences of intergenic regions. The nucleotide sequences of the genes of the IFM and IFO strains were compared with those of the H-99 and JEC 21 strains from the database. Surprisingly high similarities were found between the strains belonging in var. grubii (IFO 410 and H-99) and var. neoformans (IFM 5844 and JEC 21).

Cloning, Molecular↗
PubMed2005

Mitochondrial functioning of constitutive iron uptake mutations in Cryptococcus neoformans.

Randomly obtained, constitutive plasma membrane ferric reductase/ferrous uptake mutants of Cryptococcus neoformans were mapped to four distinct loci by meiotic analysis. One of those loci, FRR1 , was previously found homologous to MRS3 and MRS4 of Saccharomyces cerevisiae , which determine proteins involved in mitochondrial transport of iron. We were able to complement, clone, sequence and thereby identify two of the three remaining constitutive uptake loci. FRR3 was found to be homologous to ISU1 and ISU2 of S. cerevisiae, which form mitochondrial iron-sulfur complexes; FRR4 was found to be homologous to YFH1, the yeast frataxin homologue, which also participates in iron-sulfur cluster biogenesis. Because of the constitutive iron uptake seen in these mutants, mitochondria appear to have a central role in the cellular iron economy; moreover, as judged by our mutational statistics, the genetic machinery for mitochondrial iron accumulation may be more complex than that of the cytoplasm.

Amino Acid Sequence↗
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↗
PubMed2005

Expression of capsule-associated genes of Cryptococcus neoformans.

Cryptococcus neoformans produces an extracellular polysaccharide capsule that is related to its virulence. The production of capsular components was reported to be accelerated when cultured on media with lower amount of glucose. In this study, relationship between capsule synthesis and expression of capsule-associated genes (CAP genes) was investigated by quantitative real-time PCR analysis. Normally encapsulated strains and a stable acapsular strain were cultured in 1% polypepton medium with 0.1% or 15% glucose. The results of assessment of the capsule size showed that the capsule of yeast cells cultured in the medium with low amount of glucose was thicker than that with high amount of glucose. The CAP gene expressions of normally encapsulated strains were higher in the medium with 0.1% glucose than in the medium with 15% glucose. Furthermore, CAP10, CAP59 and CAP60 genes were expressed very low in a stable acapsular strain, and CAP64 gene was not expressed. Results of assessment of capsule size and CAP gene expressions by quantitative real-time PCR analysis indicated that CAP gene expressions might be related to the production of capsule, and that glucose concentration in culture media might be related to the expression of CAP genes.

Cryptococcus neoformans↗
PubMed2005

Selection of optimal host strain for molecular pathogenesis studies on Cryptococcus gattii.

Encapsulated yeast, Cryptococcus gattii (Cg) is a primary and emerging fungal pathogen in North America. It has a predilection for invading the central nervous system of both healthy and immunocompromised humans and animals. Recently, we initiated molecular pathogenesis studies in Cg strain NIH444 (ATCC 32609). In this report, we compared the biology and pathogenic potential of NIH444 to those of WM276, an Australian environmental isolate that is being used for the whole genome-sequencing project. Our data indicated that NIH444 is comparatively more virulent in a mouse model of cryptococcosis than is WM 276. We found robust mating of NIH444, and no mating of WM276, when tested against Cg MATa strain, NIH198. WM276 but not NIH444 was defective in filamentation and sporulation (haploid fruiting). Interestingly, NIH444 has a VGII/AFLP6 genotype similar to that of the genotype of the recent outbreak strains from Vancouver Island, British Columbia, Canada. Additionally, comparisons of nucleotide sequences of various genes also showed differences between NIH444 and WM276. Based on these observations, we conclude that NIH444 should remain the strain of choice for understanding Cg pathogenesis, especially on the North American continent.

Animals↗
PubMed2005

The isolation, characterization and antifungal susceptibilities of Cryptococcus neoformans from bird excreta in Klang Valley, Malaysia.

The occurrence of Cryptococcus neoformans in bird excreta in Klang valley, Malaysia was determined in this study. Of 544 samples of bird excreta collected from a local zoo, pet shops and public areas, 20 strains of C. neoformans were isolated. All C. neoformans strains were serotype A and thus identified as C. neoformans variety grubii. All did not produce color changes on canavanine-glycine-bromothymol blue agar. All were of alpha-mating types, as determined by a pheromone-specific PCR assay. The antifungal susceptibility testing using agar diffusion method Neo-sensitabs showed that all were susceptible to amphotericin B, fluconazole and itraconazole.

Animals↗
PubMed2005

DNA fingerprinting pattern and susceptibility to antifungal drugs in Cryptococcus neoformans variety grubii isolates from Barcelona city and rural environmental samples.

Cryptococcus neoformans var. grubii (serotype A) was isolated from 12 soil samples mixed with pigeon droppings (16.9%) from 71 soil samples in Barcelona and rural areas of Catalonia. C. neoformans was not isolated from indoor dust and Eucalyptus debris. PCR fingerprinting was performed in 22 representative isolates and all of them corresponded to the VNI pattern. Susceptibility testing for the 22 isolates of C. neoformans var. grubii showed that all of them were susceptible to amphotericin B. Three isolates presented MICs (Minimal Inhibitory Concentrations) > or = 1 microg/ml to Itraconazole, five MICs > or = 1 microg/ml to ketoconazole and four were fluconazole resistant, (MICs > or = 64 microg/ml), while three of them were shown to have MICs > or = 1 microg/ml to voriconazole. In spite that all isolates presented the same DNA fingerprinting pattern, the susceptibility to antifungals is very variable. The possibility of acquiring cryptococcosis infection with primarily resistant environment strains is feasible.

Amphotericin B↗
PubMed2006

A retrotransposon-derived probe for discriminating strains of Cryptococcus neoformans.

Hybridization of digested DNA to probes derived from repeated sequences has proven to be an extremely powerful epidemiologic tool for studying the relatedness of fungi. The dispersed nature of these sequences throughout the genome provides the discriminatory power for distinguishing two independent isolates from each other based on banding pattern. The genome of Cryptococcus neoformans contains a number of classes of transposable elements, which are often present in multiple copies. We characterized a probe related to the Ty3/gypsy class of transposable elements called TCN1 and used it to screen multiple isolates from all four serotypes of C. neoformans. DNA with TCN1 homology could be amplified from each isolate of serotypes A and D and all isolates hybridized to a probe derived from TCN1. Isolates from serotype B and C were also tested for the presence of a TCN1 homolog, however, only some of these isolates yielded both a TCN1-specific PCR product or hybridization signal. Comparison of the TCN1 hybridization patterns of serotypes A and D to multiple RAPD patterns of the same isolates suggested that TCN1 was more discriminating and therefore, a useful epidemiological tool.

Cryptococcosis↗
PubMed2006

An efficient method for homologous gene reconstitution in Cryptococcus gattii using URA5 auxotrophic marker.

Cryptococcus gattii (Cg) is an emerging pathogen of both healthy and immunocompromised patients worldwide. Understanding the molecular genetic basis of virulence and physiology of this pathogen will be critical for defining its pathogenic mechanisms. The purine biosynthetic gene, URA5 encoding orate phosphorybosyltransferase (OPRTase), has been successfully used as a selectable marker for gene disruption by transformation and homologous recombination in Cg. Here, we report the characterization of ura5 auxotrophy and URA5 reversion phenomenon at the molecular, genetic, and structural levels, and use of ura5-->URA5 reversion as a tool for reconstitution of gene of interest and auxotrophic marker to their native loci. We identified a single mutation of GG(128)T-->GAT with substitution of glycine to aspartic acid at amino acid position 43 resulting in ura5 auxotrophy. The ura5-->URA5 reversion on CSM lacking uracil (CSM-U) was found to be a rare phenomenon with a reversion frequency of 0.000002%, and sequence analysis of URA5 from all the reverted strains revealed mutation of GA(128)T-->GGT back to its ancestral state. The URA5 allele in the reverted strains was fully functional, as demonstrated by the excellent growth of these strains on medium lacking uracil, as well as by the ability of this allele to efficiently transform ura5 mutant to restore prototrophy. The deduced Cg URA5 protein modeled on the known crystal structures of OPRTase from Salmonella typhimurium (1LH0_A, 1STO) and from Escherichia coli (1ORO_A) indicated that the glycine 43 of Cg URA5 was situated on a conserved loop, and it's substitution to more globose aspartic acid may have resulted in URA5 inactivation in auxotrophic strain. The advantages of this approach for the generation of a reconstituted strain are (1) that it restores the functionality of the native URA5, (2) that it eliminates an additional biolistic delivery of exogenous URA5, and (3) that it allows easy selection of reconstituted strains with homologous integration. This strategy was successfully used for the generation of Cg can2+CAN2/URA5 homologous reconstituted strains, which grew in ambient air to the wild-type level while can2 mutant exhibited severe growth defect under similar conditions.

Amino Acid Sequence↗
PubMed2007

Microreview: capsule-associated genes of Cryptococcus neoformans.

Cryptococcosis, caused by Cryptococcus neoformans is a common systemic mycosis in man and animals, particularly immunocompromised patients. This pathogenic fungus produces a thick extracellular polysaccharide capsule. Four capsule-associated genes (CAP10, CAP59, CAP60, CAP64) were cloned and sequenced, and proved to be essential for capsule synthesis. However biochemical functions of CAP gene products have not been clarified yet. Recently, the relatedness of the polysaccharide capsule and four capsule-associated genes has partly been elucidated. Nucleotide sequence of four CAP gene fragments was analyzed for phylogenetic relationships, and they were in agreement with the conventional classification of varieties and serotypes within C. neoformans. Expression of four CAP genes and capsule size were examined using two media containing different amount of glucose, and the results indicated that CAP genes might play important roles in elaboration of extracellular polysaccharide capsule. Furthermore, analyses of CAP genes in various clinical samples would give the useful information to diagnose cryptococcosis in human and animals.

Animals↗
PubMed2005

Cryptococcus neoformans peritonitis in a patient with alcoholic cirrhosis: case report and review of the literature.

In the absence of coexisting HIV infection Cryptococcus neoformans is rarely considered in the differential diagnosis of peritonitis that occurs in patients with cirrhosis and ascites. Here, we report on a 39-year-old male, HIV-negative patient with decompensated alcohol toxic liver cirrhosis who developed a lethal intraperitoneal infection with C. neoformans. We reviewed the literature and found an additional 19 cases with culture confirmed cryptococcal peritonitis in combination with liver disease or AIDS. We suggest that awareness of this unusual but lethal entity may lead to earlier diagnosis and proper treatment.

Adult↗
PubMed1988

Effect of tunicamycin on xylanase secretion in the yeast Cryptococcus albidus.

The yeast Cryptococcus albidus secretes a glycosylated xylanase (48 kDa) in the culture medium in response to beta-methylxyloside as inducer. Addition of tunicamycin to the medium results in the formation of a modified xylanase (40 kDa) which is depleted in carbohydrate content and whose enzymatic activity is 2.5 times less than that of the glycosylated xylanase. The secretion of xylanase was followed under both conditions by pulse-chase experiments. The half-time of secretion of the glycosylated and nonglycosylated forms was 5 and 2 h, respectively. Cell-associated xylanase activity was not detected when the cells were treated with the antibiotic. The absence of cell wall-associated xylanase, after tunicamycin treatment, was confirmed by immunolocalization with anti-xylanase antibodies at the electron microscopic level. The results suggest that the interactions of carbohydrate moiety within the cell wall retarded the secretion of the enzyme to the medium.

Cryptococcus↗
PubMed1991

Glucuronoxylomannan of Cryptococcus neoformans serotype B: structural analysis by gas-liquid chromatography-mass spectrometry and 13C-nuclear magnetic resonance spectroscopy.

The major extracellular polysaccharide (glucuronoxylomannan, GXM) from six strains of Cryptococcus neoformans serotype B was characterized by gas-liquid chromatography (g.l.c.), g.l.c.-mass spectrometry (g.l.c.-m.s.), and nuclear magnetic resonance (n.m.r.) spectroscopy. Ultrasonic irradiation (u.i.) was used to reduce the mol.wt. of native GXM from 9.75 x 10(5) to 1.15 x 10(5) without apparent change in its composition (GXM-S). The Xylp:Manp:GlcpA molar ratio of the GXM and GXM-S from the six strains of C. neoformans serotype B is approximately 3.5:3.0:0.6. GXM-S was O-deacetylated (GXM-D) by treatment with NH4OH. The 13C-n.m.r. analysis of GXM-D gave spectra that served as characteristic fingerprints of the structure and also facilitated the assignment of the anomeric carbon resonances to specific structural moieties present in GXM-D. The GXM-D from each serotype B strain was found to be similar by 13C-n.m.r. spectroscopy. The structure contains a linear (1----3)-alpha-D-Manp backbone substituted with 2-O-beta-GlcpA and 2-O-beta-Xylp. beta-Xylp is also O-4 linked to the Manp substituted with GlcpA. In addition, a model for the disposition of the Xylp and GlcpA side chain substituents along the mannopyranan backbone is proposed, based upon results from the combination of g.l.c.-m.s. and 13C-n.m.r. spectroscopy.

Carbohydrate Sequence↗
PubMed1995

Structure of the O-deacetylated glucuronoxylomannan from Cryptococcus neoformans serotype C as determined by 2D 1H NMR spectroscopy.

The primary structure of the O-deacetylated capsular glucuronoxylomannan (GXM) isolated from Cryptococcus neoformans serotype C was investigated by 2D NMR spectroscopy. Assignment of the 1H NMR chemical shifts for the polysaccharide was accomplished from the analysis of DQF-COSY, TOCSY, NOESY and/or ROESY spectra of three isolates (298, 34, and 401). These isolates contain the same polysaccharide glycosyl residues but in different proportions. The serotype C GXM consists of two repeating polysaccharide units that have the following structures: [formula: see text] It is not known if these repeating units comprise a single or two separate polymer chains. The relative amounts of the more highly branched octasaccharide 1 in the isolates studied (i.e., approximately 75% in isolate 34, 50% in isolate 298, and 25% in isolate 401) can be used to explain the serological specificity of these isolates with C. neoformans factor sera, as was previously determined by ELISA in this laboratory. The octasaccharide 1 component is the one previously postulated as the structure of the serotype C GXM although definitive placement of the beta-Xyl-(1-->4) residues had previously not been determined. The heptasaccharide 2 component is uniformly found as the repeating unit in the polysaccharide from serotype B isolates. Additionally, GXM 401 was found to contain a small amount of the hexasaccharide repeating unit usually attributed to serotype A GXM.

Acetylation↗