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PubMed1979

The structure of the capsular polysaccharide from Cryptococcus neoformans serotype D.

The capsular polysaccharide from Cryptococcus neoformans serotype D has been studied by employing the usual methods for the elucidation of chemical structure. The results are consistent with the occurrence of a polysaccharide having both D-glucosyl-uronic acid and D-xylosyl groups present as nonreducing end-groups attached to O-2 of D-mannosyl residues which are linked alpha-D-(1 leads to 3) in a linear backbone.

Carbohydrate Conformation↗

PubMed1988

Structure determination of Cryptococcus neoformans serotype A-variant glucuronoxylomannan by 13C-n.m.r. spectroscopy.

A series of polysaccharides was derived by physical and chemical methods from an antigenic, O-acetyl-containing, glucuronoxylomannan (GXM), isolated from the growth medium of Cryptococcus neoformans (CDC B2550) serotype A-variant having composition ratios of Man:Xyl:GlcA:OAc = 10:4:3:6. 13C-N.m.r. spectra of derivatives provided new structural evidence for GXM. Treatment of GXM with Li in ethylenediamine gave a xylomannan (XM, with Man:Xyl = 5:2). Smith degradation of XM gave a mannan (M). Ultrasonic treatment of GXM gave GXM-sonicated (GXMS). Treatment of GXM with 3-(3-dimethylaminopropyl)-1-ethylcarbodiimide.HCl and then with NaBH4 gave reduced GXMS (RGXMS), or with aq. trifluoroacetic acid gave partially acid-hydrolyzed GXMS. Periodate oxidation of GXM and NaBH4 reduction of the product gave a polyalcohol-mannan (PM). Treatment of GXMS, RGXMS, and PM with NH4OH at pH 11 gave the respective O-deacetylated analogs. Comparison among the 13C-n.m.r. spectra of GXM, the various derivatives, and reference monosaccharides allowed the following conclusions: M is (1----3)-alpha-D-mannopyranan; XM consists of the M backbone with 91% of the Xyl on nonadjacent Man residues as 2-O-beta-D-Xylp substituents and with 9% as 4-O-D-Xylp substituents on other Man residues. GXM consists of the XM structure, but with non-D-xylosylated Man residues substituted with 2-O-beta-D-GlcpA substituents and with 6-O-acetyl groups distributed approximately equally on Man residues that have other substituents and those that have none. The molecular mechanics program MM2 was used to estimate the relative energies of anomeric orientations of the typical glycosidic linkage in M. The results suggest that 6'-OH----O-2 H-bonding is significant in the minimal-energy orientation of M, with phi = -36 degrees and psi = 51 degrees, and that two other glycosidic orientations may be important in the 2-O- or 6-O-substituted derivatives of M.

Cryptococcus↗

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↗

PubMed1986

The biochemical basis for the distinction between the two Cryptococcus neoformans varieties with CGB medium.

The biochemical basis for the reaction to canavanine-glycine-bromthymol blue (CGB) agar by Cryptococcus neoformans var. gattii and C. neoformans var. neoformans was investigated. All of the var. gattii isolates tested were found to utilize glycine as the sole source of carbon and nitrogen and were resistant to L-canavanine. Only 11% of the serotype D isolates of var. neoformans utilized glycine as the sole source of carbon and nitrogen, but these were all sensitive to canavanine. Nineteen percent of the serotype A isolates of var. neoformans were able to assimilate glycine, and 81% of the glycine users were resistant to canavanine. However, these canavanine-resistant, glycine-assimilating, var. neoformans isolates failed to grow when they were cultured on a medium containing glycine and canavanine. Unlike the var. neoformans isolates, all of the var. gattii isolates tested grew on a medium that contained both of these compounds. Glycine-utilizing isolates exhibited good uptake of the amino acid, and a glycine-cleaving enzyme was discernable in the isolate. The isolates that fail to utilize glycine accumulated the amino acid at a rate which was barely 15% of that seen in the glycine users, and no glycine-cleaving enzyme was apparent within the 48-hr incubation period. When a cell-free extract (which had been derived from a glycine-utilizing isolate), was incubated with 14C-labeled glycine, ammonia, radiolabeled CO2, and serine were produced. The glycine decarboxylase activity of the cell-free extract was found to be enhanced by the addition of dithiothreitol, tetrahydrofolate, pyridoxal phosphate, and nicotinamide adenine dinucleotide (NAD). The ammonia released during glycine cleavage seems to be responsible for the positive reaction on CGB medium.

Biological Transport↗

PubMed1986

The susceptibility of Cryptococcus neoformans to an antimycotic agent (G2) from alfalfa.

Compound G2, 2-beta-hydroxy-3-beta-O-(beta-D-glucopyranosyl)-delta 12-oleanene-23,28-dionic acid, isolated from alfalfa roots, demonstrated considerable activity against Cryptococcus neoformans (MIC value of 2 micrograms/ml). Compound G2 exhibited rapid killing of this fungus (MFC value of 4 micrograms/ml) suggesting that it might be a useful active agent in the treatment of cryptococcosis.

Antifungal Agents↗

PubMed1987

The brown colour effect (BCE) of Cryptococcus neoformans in the diagnosis, control and epidemiology of C. neoformans infections in AIDS patients.

Cryptococcus neoformans was found as the causative agent of cryptococcosis in 7 (3.6%) out of 195 HIV-positive persons, most of them being hospitalized. These 7 persons included 6 homosexuals and 1 heroin addict. The examinations were performed at the Mycology Unit of the Robert Koch Institute in Berlin (West) between 1984 and 1986. The brown colour effect (BCE) of the C. neoformans colonies on Guizotia abyssinica creatinine agar (with 0.1% glucose) within 2-5 days at 26 degrees C facilitated the diagnosis of disseminated cryptococcosis. In all 7 cryptococcosis cases, the antigen of C. neoformans was detected in serum and CSF by the latex agglutination test. The initial titres ranged from 1:100,000 to 1:160 in the serum and from 1:1280 to 1:10 in the CSF. In comparison to the progressive stage of the infection with the involvement of the various organs and high antigen titres, the fungus may be detected at an early stage in the respiratory tract only where low antigen titres are observed. All the C. neoformans isolates were found to belong to the variety neoformans. Proposals for an effective control of cryptococcosis are made.

Acquired Immunodeficiency Syndrome↗

PubMed1981

Roles of macrophage Fc and C3b receptors in phagocytosis of immunologically coated Cryptococcus neoformans.

I have studied the roles of macrophage Fc and C3b receptors in the cell's interaction with encapsulated Cryptococcus neoformans and have defined the effects of a lymphokine that enhances macrophage complement receptor function, the effects of ingestion of soluble immune complexes, and the effects of corticosteroid treatment upon the ability of macrophages to phagocytize cryptococci via these receptors. Neither uncoated nor C3-coated cryptococci were phagocytized, whereas IgG-coated cryptococci were avidly phagocytized by mouse peritoneal macrophages. Treatment of macrophages with the lymphokine enabled them to ingest C3-coated cryptococci. Prior ingestion of soluble immune complexes severely compromised macrophages' ability to phagocytize cryptococci via their Fc receptors but did not affect their ability to ingest cryptococci via their complement receptors. Corticosteroid treatment severely impaired the ability of macrophages to respond to the lymphokine. Based upon these experimental observations, I have constructed a model for normal host defense mechanisms against disease due to C. neoformans.

Animals↗

PubMed1976

Cryptococcus neoformans in the crops of pigeons following its experimental administration.

Cryptococcus neoformans (5 X 10(6) yeast cells) was given per os to 10 pigeons (Columba livia) proved to be free (crops and excreta) of C. neoformans prior to experimentation. The yeast was recovered from the droppings of 9 pigeons the day after ingestion but was still present in the droppings of 1 pigeon on the 22nd day after ingestion. The crop was much more constantly positive than the droppings and for a much longer time since positive in 9 pigeons on the first day it was still positive in 2 pigeons on the 86th day at the end of the observation period. The results of the experiment presented here and the results of previous work, indicate that C. neoformans can survive and could so be carried in the crop of pigeons.

Animals↗

PubMed1978

Study of the role of pigeons in the dissemination of Cryptococcus neoformans in nature.

Cryptococcus neoformans was recovered from droppings collected within the first 24 h from pigeons experimentally fed with a dose of 5 X 10(6) cells. The fungus proved to multiply well though differently in the sterilized pigeon and chicken excreta seeded with the organism. In both unsterile types of droppings no viable cells of C. neoformans were detected after 4 weeks incubation. Isolated bacterial flora from the intestinal contents of apparently healthy pigeons showed a complete inhibitory effect on the growth of C. neoforms in vitro. It has been concluded that pigeons do not favor multiplication of the fungus in their gut and consequently they do not seem to play an active biological role in dissemination of C. neoformans in nature.

Animals↗

PubMed1979

Cryptococcus neoformans: gastronomic delight of a soil ameba.

During 7 days of incubation in vitro the trophozoite stage of the free-living soil amoeba, Acanthamoeba polyphaga, phagocytized and killed 78-97% of the cells of three strains of Cryptococcus neoformans. With one strain, incubation time was increased to nine days and 99% of the yeast cells were killed. It was calculated that during 4-9 days of incubation a single trophozoite phagocytized and killed a daily average of 84 yeast cells. The lethal effect of A. polyphaga on C. neoformans may represent a biological control mechanism in nature. Some of the surviving cells of C. neoformans developed into colonies containing pseudohyphae; these pseudolhyphal forms may be a biological 'escape hatch'.

Amoeba↗

PubMed1990

Comparative morphological and biological studies on the itraconazole- and ketoconazole-resistant mutants of Cryptococcus neoformans.

Studies were carried out on the resistance in vitro of Cryptococcus neoformans to the oral antifungal drugs itraconazole and ketoconazole. None of the six sensitive strains tested developed resistance to itraconazole or ketoconazole by serial transfer on Sabouraud's glucose agar plates containing increasing concentrations of either drug. One mutant resistant to itraconazole, and one mutant resistant to ketoconazole, were isolated from the progenies of yeast cells surviving after treatment with a mutagenic substance, N-methyl-N'-nitro-N-nitroso-guanidine. These mutants were capable of growing in the presence of high concentrations of the drugs to which they were resistant. The itraconazole- and ketoconazole-resistant mutants obtained by mutagenesis were compared morphologically and biologically. The itraconazole-resistant mutant was characterized by the formation of very rough colonies which varied in size and shape, production of a large number of cell clusters, complete loss of capsule formation, and major degenerative changes in the cells, while in the ketoconazole-resistant mutant these changes were less pronounced and no cell clusters were formed. The acquisition of resistance was more stable in the itraconazole-resistant mutant than in the ketoconazole-resistant mutant. Both mutants showed partial cross-resistance and complete loss of virulence for mice.

Animals↗

PubMed1986

Poorly encapsulated Cryptococcus neoformans from patients with AIDS. II. Correlation of capsule size observed directly in cerebrospinal fluid with that after animal passage.

Cryptococcus neoformans recovered from the cerebrospinal fluid (CSF) of eight patients, seven with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC), were studied to assess the relationship between degree of encapsulation noted in fresh CSF with that observed after animal passage. We further correlated encapsulation with extent of immunodeficiency in these patients. Results of these studies showed poor encapsulation (mean capsule plus cell diameter less than 10 micron) in six patients, intermediate in one (mean 15.5 micron), and full encapsulation in one (mean 24.4 micron). The last isolate was observed in the CSF from the only patient without convincing clinical evidence for AIDS. Mouse passage of cryptococci from 5 AIDS patients and one with ARC resulted in a statistically significant (P less than 0.05) increase in capsule size over that observed directly in fresh cerebrospinal fluid. Cryptococci derived from the non-AIDS patient did not show an increase in encapsulation after mouse passage. These studies suggest that the immune deficiency state associated with AIDS exerts little selective pressure on inhaled poorly encapsulated C. neoformans.

AIDS-Related Complex↗

PubMed1975

Recovery of Cryptococcus neoformans from sputum using new technics for the isolation of fungi from sputum.

Three sputum-digesting agents, N-acetyl-l-cytseine, dithiothreitol, and pancreatin-trypsin, were shown to be equally effective in allowing for the isolation of Cryptococcus neoformans from sputum samples in quantitative comparisons. By quantitative plating on bird-seed medium it was also shown the centrifugation after digestion concentrated C. neoformans into a platable sediment and, further, that the organisms, when present in concentrations as low as 10 yeasts per ml. of sputum, could be isolated with much higher frequencies than when no digestion-centrifugation procedure was used.

Acetylcysteine↗

PubMed1986

Differentiation of Cryptococcus neoformans serotypes by isoenzyme electrophoresis.

Cryptococcus neoformans has been divided into four serotypes by specific agglutination in immune rabbit sera. Based on mating characteristics of the perfect state and epidemiologic and biochemical differences, the serotypes have been divided into two major pairs. In an attempt to characterize the serotypes further, the authors studied 22 strains of C. neoformans by the technic of horizontal starch-gel isoenzyme electrophoresis. The glucose-phosphate isomerase and phosphoglucomutase of serotypes A, C, D, and a subset of the serotype B strains migrated to distinguishable locations in this system. The activities of the remainder of the serotype B strains co-migrated with the serotype C strains. Thus, this technic distinguishes all the serotypes of C. neoformans except for a subset of serotype B and should be a useful adjunct for further elucidation of the epidemiologic and biochemical differences among serotypes.

Cryptococcus↗

PubMedDate not supplied

Role of the capsule in phagocytosis of Cryptococcus neoformans.

The capsule is closely associated with the virulence of Cryptococcus neoformans. The capsule inhibits phagocytosis by macrophages, monocytes, and neutrophils. Studies in our laboratory have shown that incubation of encapsulated cryptococci in normal human serum leads to deposition of large amounts of C3 fragments at the surface of the yeast and lesser amounts of IgG within the capsule. Thus, the capsule mediates two biologic activities with opposing effects. It is our current view that phagocytosis of the yeast is dependent on a balance between the antiphagocytic action of cryptococcal polysaccharide and the ability of the yeast to focus opsonically active complement fragments and the IgG at the capsular surface.

Animals↗

PubMedDate not supplied

Capsular polysaccharides of Cryptococcus neoformans.

Polysaccharides of Cryptococcus neoformans are considered to have a role in the virulence of this encapsulated fungus. The structure has been determined for the most abundant polysaccharide, a glucuronoxylomannan of varying xylose and ester content. The structural complexity of the capsular material increases from serotype D to A to B to C, but even for the simplest capsule (type D), the immunodeterminants seem to occur only on the side chains. The interactions of some of these groups with antibodies is discussed.

Antibodies, Fungal↗

PubMed1975

Susceptibility of coccidioides immitis, Candida albicans, and Cryptococcus neoformans to amphotericin B, flucytosine, and clotrimazole.

Toxicity and failure of treatment with amphotericin B are stimuli for researchers to evaluate alternative antifungal antimicrobics. Also, data from susceptibility tests of Coccidioides immitis are sparse. With use of a defined, synthetic culture medium, C. immitis (25 strains). Candida albicans (21 strains), and Cryptococcus neoformans (21 strains) were tested against flucytosine, clotrimazole, and amphotericin B. Molecule for molecule, the sequency of activity was: clotrimazole greater than amphotericin B greater than flucytosine (totally inactive) C. immitis; and clotrimazole greater than amphotericin B greater than flucytosine with C. albicans and C. neoformans. With four strains of C. immitis, the minimal inhibitory concentration (of amphotericin B) was the same when inocula of arthrospores were tested as when corresponding spherules/endospores were tested simultaneously and identically. The clinical outcome of coccidioidomycosis in 17 patients treated with amphotericin B correlated best with minimal inhibitory concentration after incubation of cultures for 48 hr; a favorable response was associated with minimal inhibitory concentrations of less than or equal 1.0 mug/ml. Because clinical isolates of fungi appear to vary in susceptibility, in vitro tests may have clinical utility.

Adult↗

PubMed1976

Amphotericin B and amphotericin B methyl ester ascorbate. I. Chemotherapeutic activity against Candida albicans, Cryptococcus neoformans, and Blastomyces dermatitidis in mice.

Amphotericin B methyl ester (AME) has been reported to possess in vitro antifungal activity similar to that of amphotericin B and to have less intrinsic toxicity in mice and dogs. For these reasons AME has been porposed as an alternative to amphotericin B in the therapy of deep mycoses. For comparison of the therapeutic efficacy of the two polyenes in laboratory animals before initiation of studies in humans, groups of mice were infected with Candida albicans, Cryptococcus neoformans, and Blastomyces dermatitidis. Treatment consisted of two or more doses of each drug given by the intravenous route. Concurrently, studies of subacute toxicity were conducted in the same species to permit calculation of therapeutic indices. These studies have shown that AME, as the ascorbate salt, is substantially less efficacious than amphotericin B (in colloidal dispersion with sodium deoxycholate) for treatment of the fungal infections and that amphotericin B had a higher therapeutic ratio for all infections studied than did AME.

Amphotericin B↗