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PubMedDate not supplied

[Effect of carbon and nitrogen sources on exopolysaccharide synthesis by Cryptococcus laurentii].

The effect of various carbon and nitrogen sources on the synthesis of the branched exopolysaccharide produced by Cryptococcus laurentii st 1803-K. was studied. The conditions favourable for a higher yield of the polymer were found. The carbon and nitrogen sources used do not affect the qualitative monosaccharide composition of the polysaccharide, however, the introduction of ammonium salts in the medium can cause a change in the monosaccharide ratio in the side chains of the polymer.

Carbon↗
PubMed1984

[Experimental pathogenicity of Cryptococcus cereanus in mice].

Pathogenicity studies in mice with Cryptococcus cereanus. Cr.cereanus, a yeast which showing a characteristic ability to grow above 40 degrees C, was found to induce pathogenicity when i.p. inoculated into mice after 6-7 repeated inoculations. Infected mice were sacrificed after 4, 8, 24 h and 3, 7, 14, 21 days following i.v. inoculation (5 X 10(7) cells); and microbiological, histopathological and blood-clinical tests were performed. The time course of C.F.U. in kidneys and brains (Fig.1) the yeasts colonization in heart and kidney tissues (Fig.5-3) and the characteristic "soap's balls" in brains (Fig.4) were confirmed by the modified serum levels of CPK, LDH, GOT, urea and creatinine. For the first time experimental pathogenicity of Cr. cereanus has been demonstrated.

Animals↗
PubMed1980

Effect of Listeria monocytogenes lipids on the immunity of mice against Candida albicans, Cryptococcus neoformans and Trichomonas vaginalis.

The effect of Listeria monocytogenes lipids (Lm lipids) on immunity against Candida albicans, Cryptococcus neoformans and Trichomonas vaginalis was studied in mice. The administration of Lm lipids did not affect significantly the course of T. vaginalis infection. On the other hand, single Lm lipids injection markedly decreased the mortality rate of mice with mycotic infections, and significantly accelerated the elimination of fungal cells from liver, spleen and blood circulation of animals. It is suggested that enhanced resistance of mice conferred by Lm lipids may be related to observed increase in activity of macrophages. The study demonstrated a very low toxicity of Lm lipids preparation.

Animals↗
PubMedDate not supplied

[Cytochemical study of glycogen localization and accumulation in cells of the psychrophile Cryptococcus laurentii].

The synthesis and intracellular localization of glycogen were studied cytochemically on sections and by electron-microscopic cryofractography in the psychrophilic yeast Cryptococcus laurentii under different conditions of cultivation. Glycogen synthesis started in the phase of growth deceleration at the periphery of the cell at the same time as another reserve substance (lipid inclusions) was formed. The degree of glycogen accumulation in the cytoplasm depended on the composition of the medium and the temperature of growth. The maximal accumulation of glycogen in the cels was detected at a low growth temperature (4 degrees C) in a minimal medium. Under these conditions, glycogen was a predominant component in the cytoplasm at the stationary phase of growth, and was not noticeably utilized over a long period of time. The ribosomes were scattered in a diffuse manner between glycogen granules. The results are indicative of the fact that temperature plays a significant role in glycogen synthesis and that this carbohydrate is important for survival of yeast organisms at low temperatures.

Cryptococcus↗
PubMed1981

[Morpho-biochemical differences observed on two wild strains groups of Cryptococcus albidus: V. albidus and V. diffluens (author's transl)].

The morpho-biochemical characteristics were studied on 115 wild strains of Cryptococcus albidus: 61 isolates of the variety albidus and 54 of the variety diffluens. The mucous aspect of the colony, the pigmentation, the development on liquid medium, the cells' form and the filamentation were the morphological characters observed. As for the physiology, were reported the results concerning: the fermentation, the assimilation of 24 carbohydrates and the potassium nitrate, the development according: the temperature, two rates of actidione (cycloheximide) and four rates of tetrazolium. Were discussed: the atypicity and the intra-specific variations, the differenciation of the varieties and the taxonomic value of the two entities.

Carbohydrate Metabolism↗
PubMed1994

Comparisons between in vitro glial cell adherence and internalization of non-encapsulated and encapsulated strains of Cryptococcus neoformans.

The adherence of non-encapsulated and encapsulated strains of Cryptococcus neoformans to rat glial cells in culture was compared. Like the encapsulated strain, the adherence of the unencapsulated strain was affected by the yeast culture age and growth temperature. Yeasts grown to late stationary phase at 37 degrees C were the most adherent. Neither encapsulated nor non-encapsulated strains adhered to glial monolayers when the experiments were conducted at 5 degrees C, indicating that metabolically active mammalian cells were required for yeast adherence. Additionally, the non-encapsulated strain was consistently three times more adherent than the encapsulated strain, suggesting that the non-encapsulated strain either had more adhesins or more adhesins were exposed. Electron microscope studies indicated that both strains were internalized by glial cells, an event previously not reported for this mammalian cell type. The same carbohydrates (N-acetyl-D-glucosamine, sucrose and inositol) that inhibited adherence of the encapsulated strain the most, also inhibited adherence of the non-encapsulated strain, again indicating similar adhesin mechanisms. Both encapsulated and non-encapsulated strains were made non-adherent by treatment with pronase, papain, trypsin and amylase. Immobilized amylase appeared to remove an adhesin fragment that bound to glial cells and inhibited the adherence of intact cryptococci.

Amylases↗
PubMed1995

Evidence of canary droppings as an important reservoir of Cryptococcus neoformans.

After preliminary results had shown the occurrence of Cryptococcus neoformans in canary droppings in southern Italy, the increasing epidemiological interest in cryptococcosis and the habitats of the agent led to more extensive studies. 180 samples of canary droppings were collected from pet shops and private households in two towns (Messina and Reggio Calabria) of southern Italy and culturally examined for C. neoformans. The examination was carried out with the help of the brown colour effect (BCE) specific of the C. neoformans colony on Guizotia abyssinica creatinine agar (Staib agar). 48 samples (26.6%) were positive; of these, 32/108 (29.6%) were from pet shops and 16/72 (22.2%) from private households. The colony growth was not mucous, i.e. microscopically the blastospores were found to be little or not encapsulated. All C. neoformans strains tested by the auxanographic method showed a weak assimilation of creatinine. The variety status of the isolates was tested with canavanine-glycine-bromothymol-blue (CGB) agar; all strains tested (n = 420) were found to be C. neoformans var. neoformans. In the light of extensive studies on C. neoformans and the canary in the pre-AIDS era in Germany, the present observations in Italy ask for further basic research, epidemiological studies, and education of the public.

Animals↗
PubMedDate not supplied

Iron acquisition by Cryptococcus neoformans.

Iron is an essential element for the growth and metabolism of microbial cells. Most pathogenic microbes elaborate powerful iron chelating agents (siderophores) to mobilize iron from ferric ligands. The pathogenic yeast, Cryptococcus neoformans has not been found to produce siderophores and its mechanism of iron acquisition is unknown. This investigation explored an alternative pathway for iron acquisition by examining the interactions of iron with the cell surface. Iron uptake experiments were conducted utilizing radiolabelled ferrous iron and ferric iron chelates, with evidence for the presence of iron(II) receptors and the generation of ferrous iron by surface reduction. Hyperbolic kinetics were found when 59FeII was presented to the organism and uptake was blocked with bathophenanthroline sulphonate, an Fe2+ chelator. The yeast also acquired iron as [59Fe3+]-citrate and [59Fe3+]-pyrophosphate while bathophenanthroline sulphonate reduced the acquisition of these ferric ligands by 48% and 52% respectively. Pre-incubation with either ferric ligand also reduced iron acquisition by 50%. KCN inhibited uptake of iron(II) by 90% and uptake of [59Fe3+]-pyrophosphate and [59Fe3+]-citrate by 46% and 56% respectively; dinitrophenol had no effect on these processes. The data suggest that C. neoformans can (i) generate ferrous iron at the cell surface via a reduction of ferric chelates, with the subsequent acquisition of the ferrous iron, and (ii) acquire iron through the interaction of ferric chelates with a surface component.

Citrates↗
PubMed1993

Combined histochemical stains in the differential diagnosis of Cryptococcus neoformans.

Three combinations of histochemical stains were used to study 69 routinely processed tissues containing various "yeast-like" fungal organisms (Cryptococcus neoformans, Blastomyces dermatitidis, Coccidioides immitis, Histoplasma capsulatum, Paracoccidioides brasiliensis, and Candida albicans). Fontana-Masson stain combined either with mucicarmine or Alcian blue produced distinctive staining of C. neoformans (Fontana-Masson-positive wall and mucin-positive capsule) that was not identified in other fungi. The Alcian blue stain combined with periodic acid-Schiff reaction also was useful for fungal classification, because the Alcian blue component reacted with only C. neoformans (capsule) and B. dermatitidis (wall) and the periodic acid-Schiff reaction reacted with the cell wall and body of each fungus. We concluded that the combined histochemical stains used in conjunction with morphologic study of hematoxylin and eosin- and Gomori methenamine silver-stained sections are helpful in the differential diagnosis of yeast-like fungal organisms.

Alcian Blue↗
PubMed1993

Depletion of murine CD8+ T cells in vivo decreases pulmonary clearance of a moderately virulent strain of Cryptococcus neoformans.

Host defense mechanisms to the important fungal pathogen Cryptococcus neoformans are complex and incompletely understood. From in vitro studies, we could expect CD8+ T cells to have the potential for both protective and suppressive effects on defense against cryptococci. The current study used the technique of in vivo subset depletion to determine the net effect of CD8+ T cells during actual infection. Mice depleted of CD8+ T cells by monoclonal antibody (YTS 169.4) injections were infected with the moderately virulent cryptococcal strain 613D by the intratracheal route, which mimics natural pulmonary infection. To ensure adequacy of depletion, T cell subsets were enumerated by flow cytometry in blood, spleen, lymph node, and lung. Specific elements of host defense were measured by clearance of cryptococci in vivo and by the response to cryptococcal antigens, both in vivo by delayed-type hypersensitivity (DTH) and in vitro by lymphocyte proliferation. We found that depletion of CD8+ T cells decreased pulmonary clearance of C. neoformans. CD8 depletion abrogated DTH without affecting antigen recognition or lymphocyte proliferation in vitro. These data demonstrate that the net effect of CD8+ T cells to a moderately virulent strain of C. neoformans is to enhance rather than suppresses host defenses. Abrogation of DTH suggests that CD8+ T cells contribute to the protective immunologic response to C. neoformans. It is possible that in hosts deficient in CD4 cells, such as patients with AIDS, the protective effects of CD8+ T cells could be stimulated by selected immunizing epitopes.

Animals↗
PubMed1994

Biochemical basis for the killing of Cryptococcus neoformans by rat peritoneal cells.

The biochemical basis of peritoneal cell cytotoxicity for Cryptococcus neoformans was studied by measuring the killing of the yeast by peritoneal resident cells and peritoneal exudate cells obtained from normal and proteose-peptone-injected animals, respectively. Both cell populations killed C. neoformans to an equivalent extent after 3 h incubation. Exudate cells showed anti-cryptococcal activity from the first hour of incubation, while no killing was observed with resident cells before 3 h. Both cell populations triggered a respiratory burst in response to opsonized C. neoformans as indicated by the fact that killing of the yeast was inhibited by scavengers of reactive oxygen intermediates (ROI). C. neoformans susceptibility to H2O2 and hydroxyl radicals in cell-free systems is demonstrated by incubating a yeast suspension with different concentrations of H2O2 and Fenton's reagents, respectively. These results suggest that oxygen metabolites play an active role in C. neoformans killing.

Animals↗
PubMed1995

Isotype switching from IgG3 to IgG1 converts a nonprotective murine antibody to Cryptococcus neoformans into a protective antibody.

Passively administered mAbs to Cryptococcus neoformans capsular polysaccharide can alter the course of infection in mouse models. In preliminary studies of passive Ab efficacy, most IgM, IgA, and IgG1 mAbs were protective, but the few IgG3 mAbs tested did not confer significant protection. Because IgG3 is effective in pneumococcal infections, this phenomenon was examined more rigorously by generating an IgG1 switch variant from the non-protective IgG3 mAb 3E5 and comparing its protective efficacy in a murine model of i.v. infection by using strains of both the A and D serotypes. The 3E5 IgG3 mAb did not prolong survival or reduce organ fungal burden. Rather, the IgG3 decreased survival relative to controls. In contrast, the IgG1 switch variant of 3E5 significantly prolonged survival, reduced organ colony-forming units, and reduced serum polysaccharide Ag level in infected mice. The results establish that isotype is important for Ab efficacy against C. neoformans.

Animals↗
PubMed1994

Strains of Cryptococcus neoformans with defined capsular phenotypes.

The polysaccharide capsule is a virulence factor in the opportunistic yeast pathogen, Cryptococcus neoformans. We describe a collection of strains which were isolated or constructed to exhibit defined capsular phenotypes. The collection includes strains with wild-type, acapsular and hypercapsular traits.

Cryptococcus neoformans↗
PubMed1994

Prostatic sequestration of Cryptococcus neoformans in immunocompromised persons treated for cryptococcal meningoencephalitis.

We report a case of a patient with acquired immune deficiency syndrome who was successfully treated for cryptococcal meningoencephalitis with amphotericin B and 5-flucytosine. He died from other sequelae of acquired immune deficiency syndrome two years later. An autopsy revealed prominent cryptococcal prostatitis. Cryptococci were neither found in the central nervous system nor in other anatomic sites. The autopsy files yielded seven other cases of men with a history of cryptococcal meningoencephalitis. The possibility that the prostate sequesters Cryptococcus neoformans thereby contributing to systemic relapse is explored. The qualify as a sequestration, cyptococci must be cultured from the prostate, or from a midstream voided specimen after prostatic massage, and the prostate must be the only focus of infection.

AIDS-Related Opportunistic Infections↗
PubMed1976

Caprine mastitis due to Cryptococcus neoformans.

The isolation of Cryptococcus neoformans from milk and its demonstration by direct microscopy has been reported in a case of caprine mastitis. This is believed to be the first instance of caprine mastitis in which C. neoformans has been implicated as the etiologic agent.

Animals↗
PubMed1994

Melanin-deficient mutants of Cryptococcus neoformans.

Cryptococcus neoformans is a significant fungal pathogen in immunocompromised patients. The ability of C. neoformans to produce melanin has been correlated with virulence. The role of melanin in promoting virulence is unclear, although an anti-oxidant function has been suggested. To begin to define the genetic mechanisms responsible for melanin production in C. neoformans, we describe the isolation of seven melanin-deficient mutant classes. Some of the mutants can be suppressed by addition of Cu2+ to media, suggesting that the phenoloxidase of C. neoformans, like other fungal phenoloxidases, contains copper. Other mutants display a recessive sterile phenotype. A genetic and phenotypic characterisation of these mutants is presented.

Crosses, Genetic↗
PubMed1994

Cryptococcus neoformans vertebral osteomyelitis.

A 67-year-old previously healthy woman presented with low back pain of 2 months duration and daily fever of 39 degrees C for 3 weeks. CT scan showed a lytic lesion in the third lumbar vertebra and a small right lower lobe lung infiltrate with mediastinal lymphadenopathy. Culture of material obtained from open biopsy of the vertebra grew Cryptococcus neoformans var. neoformans, which was also demonstrated on histology. Cryptococcal antigen was detected in the patient's serum. Treatment with amphotericin B (1000 mg total dose) and oral 5-fluorocytosine, resulted in complete recovery and resolution of the chest X-ray findings with a follow-up of 2 years. Since this case, as well as most of the previously described cases of cryptococcal osteomyelitis, were in normal hosts, cryptococcal osteomyelitis should be considered in the differential diagnosis even in a normal host, and therefore, prior to possible invasive diagnostic procedures, cryptococcal antigen in the serum should be determined.

Aged↗
PubMed1994

Experimental murine pulmonary cryptococcosis. Differences in pulmonary inflammation and lymphocyte recruitment induced by two encapsulated strains of Cryptococcus neoformans.

BACKGROUND: Cryptococcus neoformans, the most common cause of lethal mycosis in AIDS, usually causes only subclinical pneumonitis in normal hosts. However, cryptococcosis can induce various pulmonary inflammatory reactions, and pulmonary cellular immunity is postulated to prevent dissemination. We hypothesized that cryptococcal strains possess different capacities to induce recruitment to the lungs of inflammatory cells, especially lymphocytes, which are necessary for cryptococcal clearance. EXPERIMENTAL DESIGN: We examined the pulmonary response of CBA/J mice to intratracheal inoculation with C. neoformans of either of two strains: 52D (ATCC 24067), which rarely kills immunocompetent mice; and 145A (ATCC 62070), which is uniformly fatal. From 2-42 days after inoculation, lungs were either examined grossly and microscopically or were enzymatically digested and inflammatory cells counted and analyzed by flow cytometry. At 42 days, organism burden in lung and brain was quantified by colony-forming unit assay. RESULTS: Pulmonary inflammation differed greatly between the two strains. Strain 52D induced dense perivascular and alveolar inflammation; infection progressed to day 21 and then waned. In contrast, strain 145A induced delayed, meager lymphocytic infiltration and slight alveolitis; organisms grew progressively. Recovery of inflammatory cells increased by day 13 with strain 52D, but not until day 31 with strain 145A. Although all lymphocyte subsets were greater in 52D infection, the disparity was greatest for CD4+ T cells. Nevertheless, lymphocytes from paratracheal nodes of infected mice proliferated in vitro to heat-killed cryptococci, indicating immune recognition of both strains. At day 42, strain 52D lightly infected lungs but not brain, whereas strain 145A heavily infected lungs and brain. CONCLUSIONS; Cryptococcal strains differ in their capacity to induce pulmonary cellular inflammation, especially CD4+ T cell recruitment. Our results suggest that strain-specific difference in the organism's ability to induce (or evade) pulmonary inflammation contributes to the outcome of infection.

Animals↗

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