SEARCH · Search PubMed
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.
Thirty six clinical isolates of Cryptococcus neoformans were tested for their susceptibility to 5-fluorocytosine and amphotericin B by the determination of minimum inhibitory concentrations and minimum fungicidal concentrations. 22.2% of the isolates were resistant to 5-fluorocytosine and 36.1% indicated 5-fluorocytosine tolerance. All strains were sensitive to amphotericin B.
Twenty seven autochtonous isolates of Cryptococcus neoformans from different parts of the country were studied. The analysis indicated the following serotype distribution: 63% Serotype A, 29.6% Serotype B, 3.7% Serotype D and 3.7% belonging to C. neoformans var gattii.
A sensitive enzyme-linked immunosorbent assay (ELISA) to measure antibodies against capsular polysaccharide was developed, based on the enhanced binding of polysaccharide to polystyrene microtitration plates. The wells of the microtitration plate were primed with an adipic acid dihydrazide derivative of bovine serum albumin (AH-BSA) (100 micrograms/mL, 0.01 M NaPO4-0.14 M NaCl, pH 7.2 (PBS]. Capsular polysaccharide, the glucuronoxylomannan of Cryptococcus neoformans serotype A, was oxidized with NaIO4 for 5 min; the reaction was then quenched with ethylene glycol. The partially oxidized polysaccharide was dialyzed vs. PBS, and its concentration was adjusted to 50 micrograms/mL with PBS. This solution (100 microL/well) was covalently bound to the AH-BSA primed microtitration plates through formation of a Schiff base between the hydrazide group on the AH-BSA and the aldehyde groups on the polysaccharide. Antimouse IgG-alkaline phosphatase conjugate was used in an indirect ELISA to measure captured murine monoclonal antibodies directed against glucuronoxylomannan. Mean absorbances, after 15 min, were 0.13 in negative control wells, and greater than 0.7 in test wells. No intermediate steps were required to block nonspecific binding of antibody.
Cryptococcus neoformans strains from 26 individual patients with acquired immunodeficiency syndrome (AIDS) and three isolates from patients without AIDS were tested for their susceptibility to amphotericin B, flucytosine, ketoconazole, and miconazole nitrate. Ninety percent of the C neoformans isolates from patients with AIDS were inhibited by drug concentrations within achievable serum levels. The minimum fungicidal concentration of the four tested antifungal agents, however, exceeded obtainable cerebrospinal fluid levels.
We investigated whether C1q, a subunit of the first component of C, could modulate human peripheral blood monocyte-mediated phagocytosis of Cryptococcus neoformans (CN). Adherence of monocytes to C1q-coated surfaces induced a significant enhancement of ingestion of CN blastospores that had been opsonized with specific anticapsular IgG (IgG-CN). Additionally, C1q enhanced the monocyte-mediated phagocytosis of CN opsonized with C (CN-absorbed, nonimmune, normal human serum; C-CN). Ingestion of IgG- and C-CN by control and C1q-stimulated monocytes was maximal by 1 h of incubation. The monocyte-mediated enhancement of phagocytosis caused by C1q was paralleled by a proportionate increase in fungicidal activity, an effect which was maximal by 3 h of incubation. Human serum albumin-adherent, control monocytes exhibited only a low level of killing after 3 h of incubation. C1q enhancement was blocked by preincubation of the surfaces with a goat, polyclonal F(ab')2 anti-C1q. This study describes a new cellular function for the cell surface C1q receptor: the enhancement of phagocytosis of a pathogenic organism by monocytes.
Mitosis in Cryptococcus neoformans was examined by electron microscopy. Observation of serial sections showed that the separation of chromosomes occurred in the karyokinetic nucleus in the bud, that the microtubule organizing center (MTOC) was composed of two globular elements and a bridged middle piece, and that the nuclear envelope of the karyokinetic nucleus was partially destroyed during mitosis. These findings are similar to those reported in the heterobasidiomycetous yeasts. In addition, some of the prophase cells showed extension of the karyokinetic nucleus into the bud unaccompanied by the MTOC and swelling of the middle piece of the MTOC.
Low-iron minimal medium supported growth of Cryptococcus neoformans but spent medium contained no hydroxamates, organic acids or other iron chelators. Exogenous deferoxamine stimulated growth in extreme iron-limitation, while neither organic acids nor quartersaturated transferrins were stimulatory. These results suggest two iron uptake mechanisms, one dependent upon exogenous hydroxamate, the other hydroxamate-independent.
Thermal death of Cryptococcus neoformans in the presence of amphotericin B was strongly dependent upon the temperature of pre-incubation. The entropy coefficient, that is, the increase in entropy of activation of thermal death per square unit concentration of the drug in the medium, was 35 times higher after pre-incubation at 25 degrees C than at 39 degrees C. This means that C. neoformans cells grown at lower temperatures were much more sensitive to the temperature-dependent fungicidal effect of amphotericin B.
Previous reports have demonstrated that natural killer (NK) cells are capable of inhibiting the growth of Cryptococcus neoformans in vitro, and recent studies indicate that adoptively transferred NK cell-enriched spleen cell populations enhance clearance of cryptococci from the tissues of cyclophosphamide-pretreated recipients. The primary objective of these studies was to confirm that NK cells participate in early clearance of C. neoformans in vivo. Secondarily, the anti-cryptococcal activities of polymorphonuclear leukocytes and macrophages were examined. Seven-week-old C57BL/6 bg/+ mice, which have normal levels of NK cell activity, were compared with their bg/bg littermates, which have impaired NK cell function. One and 3 days after injecting both groups of mice i.v. with 2 X 10(4) cryptococci, we assessed the NK cell activities in spleens, lungs, and livers and clearance of the organism from corresponding tissues as determined by the mean log10 numbers of cryptococcal colony-forming units (CFU) per organ. Three days postinfection, the mean numbers of cryptococcal CFU in lungs and spleens of bg/+ mice were significantly lower than in the corresponding organs of bg/bg mice. NK cell activities in spleens and lungs of bg/+ mice were significantly higher than were the NK cell activities in similar cell populations from bg/bg mice. In contrast, the mean numbers of cryptococcal CFU in livers of the two groups of animals were nearly equivalent, a situation not unexpected, since liver NK cell activities were extremely low and similar in both groups of animals. Although these data indicated a correlation between early clearance of cryptococci from tissues and levels of NK cell activities in the corresponding tissues, it was also possible that differences in phagocytic cell function between the bg/+ and bg/bg animals could account for the observed differences in clearance of cryptococci from the tissues. Therefore, phagocytic cells from the two groups of animals were compared with respect to their abilities to phagocytize and inhibit the growth of cryptococci and to their abilities to respond to chemotactic stimuli in vivo. Peritoneal PMNL from bg/+ and bg/bg mice were similar in their abilities to phagocytize and inhibit the growth of cryptococci, as well as in their chemotactic responses to viable cryptococci or sodium caseinate. In addition, there were no differences in splenic macrophage functions between the two groups of mice.(ABSTRACT TRUNCATED AT 400 WORDS)
Protoplasts were quickly and efficiently produced from both varieties of Cryptococcus neoformans and from C. laurentii by use of the multi-enzyme product Novozym 234. Conditions for regeneration of protoplasts are described. DNA yield from the Novozym-produced protoplasts was superior to that from snail gut enzyme-derived protoplasts.
In February and March 1984, Cryptococcus neoformans was detected in the manure and ambient air of a volery in the Berlin Zoo in which a Palm Cockatoo (Probosciger aterrimus) was kept. Both times, 5 colony-forming units of Cr. neoformans could be isolated on the differential medium, Guizotia abyssinica creatinine agar, from 40 1 of air aspirated by the Reuter Centrifugal Sampler (RCS). The absence of a concurrent growth of moulds was found to be of special importance for the optimal isolation of Cr. neoformans on the above mentioned agar for purposes of epidemiological research into airborne dissemination of the fungus. The advantages and disadvantages of 0.1% biphenyl to inhibit concurring growth of moulds are discussed. The control of habitats and foci of Cr. neoformans in zoos and similar establishments is considered a necessity, to prevent inhalatory exposure of susceptible, e.g. immuno-compromised persons.
The DAPI (4',6-diamidino-2-phenylindole)-fluorochrome was used to demonstrate phagocytized Cryptococcus neoformans using the mouse peritoneal cavity technique. These yeast cells were chosen because they are large and their capsules exhibit a deep yellow fluorescence which contrasts very well with the blue fluorescent nuclei of the phagocytes (preferentially macrophages). In other words, DAPI stains both, acid mucopolysaccharides and nuclear DNA. The capacity of the phagocyte nuclei to surround or even enclose the yeast cells was the most remarkable result. Generally, the application of DAPI in these phagocytosis experiments provides valuable information rapidly, easily and specifically.
The global distribution of 96 clinical isolates of Cryptococcus neoformans var. gattii among a total of 725 C. neoformans isolates was investigated. While C. neoformans var. gattii was not found among isolates obtained from Europe (excluding the United Kingdom) and Japan; and it was found only infrequently in North America (excluding Southern California), the United Kingdom, New Zealand, and Argentina; the variety was prevalent in regions with tropical to subtropical climates such as South East Asia, Southern California, Brazil, Mid to South Pacific, and the central part of Africa. Among the isolates of C. neoformans var. gattii in our collection, serotype B predominanted (77 of 96), and the serotype C isolates were almost exclusively from North America.
Thirty-two isolates of Cryptococcus neoformans from patients and one from the wild obtained in Japan were characterized for their serotype, self-fertility, and mating behaviour by crossing them with two mating types of Filobasidiella neoformans var. neoformans and F. neoformans var. bacillispora. Of the 32 isolates from patients, 31 were of serotype A and the remaining one was of serotype D. Although these 32 isolates were all self-sterile, 23 serotype A and one serotype D isolates produced a complete sexual state when mixed with the alpha mating type of F. neoformans var. neoformans. The one natural isolate was of serotype A-D and self-fertile. The Japanese clinical isolates of C. neoformans appear to be predominantly serotype A and alpha mating type of F. neoformans var. neoformans as is the case in the U.S.A.
Immune responses, including lymphocyte transformation and protection, were evaluated in a new model of experimental murine cryptococcosis. Newly developed, genetically stable, acapsular mutants of Cryptococcus neoformans were used to immunize C3H/HeN mice. Intraperitoneal and subcutaneous routes of immunization without adjuvant were studied. Spleen cells and pooled popliteal and inguinal lymph node cells responded significantly to heat-killed, whole-cell C. neoformans antigen but not to Candida albicans antigen in lymphocyte transformation assays. No significant difference in lymphocyte transformation response to antigens was observed between intraperitoneally and subcutaneously immunized animals. Mean survival time of immunized mice was extended significantly in comparison to controls following intravenous challenge with virulent C. neoformans. Degree of protection was independent of route of immunization but dependent upon the magnitude of the challenge inoculum. This model should prove valuable in the study of immunoregulation of cryptococcosis and vaccine development.
Cryptococcus neoformans causes meningitis and disseminated infection in healthy individuals, but more commonly in hosts with defective immune responses. To study the role of immune lymphocytes in protection and recovery from this infection, in vitro lymphocyte proliferative responses to whole killed organisms were characterized in normal controls and in patients with cryptococcosis. Several differences were found between these two groups. All normal individuals were found to have significant proliferative responses to cryptococci in vitro; however, patients recovering from infection had accelerated and augmented responses. Patients' T cells, but not control T cells, were found to produce interleukin 2 (IL 2) during initial stimulation in vitro. After in vitro priming, mononuclear cells from normal controls rechallenged with cryptococci in vitro demonstrated accelerated kinetics and IL 2 production similar to that of cells from recovering patients. Proliferative responses in normals required T cells and antigen-presenting cells, and resulted in an increase in the proportion of T8+ and Tac+ cells in the responding population by the ninth day of primary stimulation. An increase in Tac+ cells, but not T8+ cells, was found by the fourth day of secondary stimulation. These results demonstrate in vivo acquisition of T cell responsiveness to the organism in this small group of recovering patients, and in vitro acquisition of T cell recognition of this antigen by normal T cells during primary stimulation. The data suggest that these responses represent in vitro priming to cryptococci and indicate a role for the T8+ lymphocyte subpopulation, both unusual findings for previously described in vitro responses to soluble antigens.
Antibodies against the major capsular polysaccharide of Cryptococcus neoformans, glucuronoxylomannan (GXM), and a minor secreted polysaccharide, galactoxylomannan (GalXM), were surveyed by indirect enzyme immunoassay (EIA) in patients with cryptococcosis, with other mycoses, and in normal controls. Measurement of IgG levels against GalXM revealed cross reactions in candidiasis patients that were reduced by adsorption with Candida albicans cell walls. Measurement of IgM levels were subject to fewer cross reactions. The combination of adsorption with C albicans cell walls and measurement of IgM detected antibodies in 12 of 55 cryptococcosis patients. An end point equal to or greater than a titer of 1/16 excluded reactions in normals and limited cross reactivity in candidiasis patients to below 7%. This test has potential diagnostic significance in cryptococcosis patients who show no evidence of cryptococcal antigen circulating in the cerebrospinal fluid or serum. Reactions in this IgM assay were not spuriously due to rheumatoid factor. The major capsular GXM was much less serologically active and was subject to cross reactions with agents of bacterial sepsis. The specificity of the GalXM is directed mainly by the mannose and to a lesser extent by galactosyl residues.
Isolation of Cryptococcus neoformans is enhanced when methyl violet at 2 mg l-1 is added to the usual Guizotia abyssinica medium. In preliminary tests the medium has also proved useful for isolating C. neoformans from other sources.