Cryptococcus mollis Kützing,type species of the genus Cryptococcus: investigation of the type material

The legitimacy of the name Cryptococcus mollis for the type of the genus Cryptococcus is shown. The type material, available in the Rijksherbarium at Leiden University was investigated by transmission electron microscopy. The cell wall of most of the cells showed a structure, similar to that of basidiomycetous yeasts. Bud scars were also found.     

How does Cryptococcus get its coat?

During the past few decades, increasing attention has focused on pathogenic fungi both as fascinating research subjects and as the agents of serious illness in diverse patient populations. In particular, opportunistic fungi such as Cryptococcus neoformans command notice as the ranks of their immunocompromised victims grow. C. neoformans is unique among fungal pathogens for its major virulence factor, a complex polysaccharide capsule. In this article, our current understanding of the structure and biosynthesis of the capsule is reviewed, as are the many questions that remain to be answered about how Cryptococcus gets its coat.     

αADα Hybrids of Cryptococcus neoformans: Evidence of Same-Sex Mating in Nature and Hybrid Fitness

Cryptococcus neoformans is a ubiquitous human fungal pathogen that causes meningoencephalitis in predominantly immunocompromised hosts. The fungus is typically haploid, and sexual reproduction involves two individuals with opposite mating types/sexes, α and a. However, the overwhelming predominance of mating type (MAT) α over a in C. neoformans populations limits α–a mating in nature. Recently it was discovered that C. neoformans can undergo same-sex mating under laboratory conditions, especially between α isolates. Whether same-sex mating occurs in nature and contributes to the current population structure was unknown. In this study, natural αADα hybrids that arose by fusion between two α cells of different serotypes (A and D) were identified and characterized, providing definitive evidence that same-sex mating occurs naturally. A novel truncated allele of the mating-type-specific cell identity determinant SXI1α was also identified as a genetic factor likely involved in this process. In addition, laboratory-constructed αADα strains exhibited hybrid vigor both in vitro and in vivo, providing a plausible explanation for their relative abundance in nature despite the fact that AD hybrids are inefficient in meiosis/sporulation and are trapped in the diploid state. These findings provide insights on the origins, genetic mechanisms, and fitness impact of unisexual hybridization in the Cryptococcus population.     

Retrospective Study of the Epidemiology and Clinical Manifestations of Cryptococcus gattii Infections in Colombia from 1997–2011

Background

Cryptococcosis due to Cryptococcus gattii is endemic in various parts of the world, affecting mostly immunocompetent patients. A national surveillance study of cryptococcosis, including demographical, clinical and microbiological data, has been ongoing since 1997 in Colombia, to provide insights into the epidemiology of this mycosis.

Methodology/Principal Findings

From 1,209 surveys analyzed between 1997–2011, 45 cases caused by C. gattii were reported (prevalence 3.7%; annual incidence 0.07 cases/million inhabitants/year). Norte de Santander had the highest incidence (0.81 cases/million/year), representing 33.3% of all cases. The male: female ratio was 3.3∶1. Mean age at diagnosis was 41±16 years. No specific risk factors were identified in 91.1% of patients. HIV infection was reported in 6.7% of patients, autoimmune disease and steroids use in 2.2%. Clinical features included headache (80.5%), nausea/vomiting (56.1%) and neurological derangements (48.8%). Chest radiographs were taken in 21 (46.7%) cases, with abnormal findings in 7 (33.3%). Cranial CT scans were obtained in 15 (33.3%) cases, with abnormalities detected in 10 (66.7%). Treatment was well documented in 30 cases, with most receiving amphotericin B. Direct sample examination was positive in 97.7% cases. Antigen detection was positive for all CSF specimens and for 75% of serum samples. C. gattii was recovered from CSF (93.3%) and respiratory specimens (6.6%). Serotype was determined in 42 isolates; 36 isolates were serotype B (85.7%), while 6 were C (14.3%). The breakdowns of molecular types were VGII (55.6%), VGIII (31.1%) and VGI (13.3%). Among 44 strains, 16 MLST sequence types (ST) were identified, 11 of them newly reported.

Conclusions/Significance

The results of this passive surveillance study demonstrate that cryptococcosis caused by C. gattii has a low prevalence in Colombia, with the exception of Norte de Santander. The predominance of molecular type VGII is of concern considering its association with high virulence and the potential to evolve into outbreaks.     

Macrophage–Cryptococcus Interactions: An Update

Cryptococcus species are fungal pathogens that are a leading cause of mortality. Initial inoculation is through the pulmonary route and, if disseminated, results in severe invasive infection including meningoencephalitis. Macrophages are the dominant phagocytic cell that interacts with Cryptococcus. Emerging theories suggest that Cryptococcus microevolution in macrophages is linked to survival and virulence within the host. In addition, Cryptococcus elaborates virulence factors as well as usurps host machinery to establish macrophage activation states that are permissive to intracellular survival and replication. In this review, we provide an update of the recent findings pertaining to macrophage interaction with Cryptococcus and focus on new avenues for biomedical research.     

Peroxisomal and Mitochondrial β-Oxidation Pathways Influence the Virulence of the Pathogenic Fungus Cryptococcus neoformans

An understanding of the connections between metabolism and elaboration of virulence factors during host colonization by the human-pathogenic fungus Cryptococcus neoformans is important for developing antifungal therapies. Lipids are abundant in host tissues, and fungal pathogens in the phylum basidiomycota possess both peroxisomal and mitochondrial β-oxidation pathways to utilize this potential carbon source. In addition, lipids are important signaling molecules in both fungi and mammals. In this report, we demonstrate that defects in the peroxisomal and mitochondrial β-oxidation pathways influence the growth of C. neoformans on fatty acids as well as the virulence of the fungus in a mouse inhalation model of cryptococcosis. Disease attenuation may be due to the cumulative influence of altered carbon source acquisition or processing, interference with secretion, changes in cell wall integrity, and an observed defect in capsule production for the peroxisomal mutant. Altered capsule elaboration in the context of a β-oxidation defect was unexpected but is particularly important because this trait is a major virulence factor for C. neoformans. Additionally, analysis of mutants in the peroxisomal pathway revealed a growth-promoting activity for C. neoformans, and subsequent work identified oleic acid and biotin as candidates for such factors. Overall, this study reveals that β-oxidation influences virulence in C. neoformans by multiple mechanisms that likely include contributions to carbon source acquisition and virulence factor elaboration.     

Genotypic and Phenotypic Analyses of Two “Isogenic” Strains of the Human Fungal Pathogen Cryptococcus neoformans var. neoformans

Mycopathologia - The Cryptococcus neoformans species complex is a model organism for fungal studies. Many studies have used two strains, JEC20 and JEC21, and their derivatives. These two strains...     

Molecular diversity of serial Cryptococcus neoformans isolates from AIDS patients in the city of São Paulo, Brazil

Despite highly active anti-retroviral therapy, cryptococcal meningoencephalitis is the second most prevalent neurological disease in Brazilian AIDS patients, being frequently a defining condition with several episodes. As knowledge of Cryptococcus neoformans isolates in the same episode is critical for understanding why some patients develop several episodes, we investigated the genotype characteristics of C. neoformans isolates in two different situations. By pulsed field gel electrophoresis and random amplified polymorphic DNA analysis, 54 isolates from 12 patients with AIDS and cryptococcosis were analyzed. Group 1 comprised 39 isolates from nine patients with a single episode and hospitalization. Group 2 comprised 15 isolates from three patients with two episodes and hospitalizations. Except for three patients from group 1 probably infected with a single C. neoformans isolate, the other nine patients probably were infected with multiple isolates selected in different collection periods, or the infecting isolate might have underwent mutation to adapt and survive the host immune system and/or the antifungal therapy. However, the three patients from group 2 presented genetic diversity among isolates collected in both hospitalizations, possibly having hosted the initial isolate in both periods. These data, emphasize that Cryptococcus diversity in infection can contribute to strategies of treatment and prevention of cryptococcosis.     

In vitro susceptibility characteristics of Cryptococcus neoformans varieties from AIDS patients in Goiânia, Brazil

Sixty clinical isolates of Cryptococcus neoformans from AIDS from Goiania, state of Goiás, Brazil, were characterized according to varieties, serotypes and tested for antifungal susceptibility. To differentiate the two varieties was used L-canavanine-glycine-bromothymol blue medium and to separate the serotypes was used slide agglutination test with Crypto Check Iatron. The Minimal Inhibitory Concentration (MIC) of fluconazole, itraconazole, and amphotericin B were determined by the National Committee for Clinical Laboratory Standards macrodilution method. Our results identified 56 isolates as C. neoformans var. neoformans serotype A and 4 isolates as C. neoformans var. gattii serotype B. MIC values for C. neoformans var. gattii were higher than C. neoformans var. neoformans. We verified that none isolate was resistant to itraconazole and to amphotericin B, but one C. neoformans var. neoformans and three C. neoformans var. gattii isolates were resistant to fluconazole. The presence of C. neoformans var. gattii fluconazole resistant indicates the importance of determining not only the variety of C. neoformans infecting the patients but also measuring the MIC of the isolate in order to properly orient treatment.     

Cryptococcus gattii, No Longer an Accidental Pathogen?

Cryptococcus gattii is an environmentally occurring pathogen that is responsible for causing cryptococcosis marked by pneumonia and meningoencephalitis in humans and animals. C. gattii can form long-term associations with trees and soil resulting in the production of infectious propagules (spores and desiccated yeast). The ever-expanding number of reports of clinical and environmental isolation of C. gattii in temperate climates strongly imply that C. gattii occurs worldwide. The key ability of yeast and spores to enter, survive, multiply, and exit host cells, and to infect immunocompetent hosts distinguishes C. gattii as a primary pathogen and suggests evolution of C. gattii pathogenesis as a result of interaction with plants and other organisms in its environmental niche. Here we summarize the historical literature on C. gattii and recent literature supporting the worldwide occurrence of the primary pathogen C. gattii.     

First isolation and molecular characterization of Cryptococcus neoformans var. grubii in excreta of birds in the urban perimeter of the Municipality of Popayán,Colombia

Background

Cryptococcosis is a systemic opportunistic mycosis, caused by Cryptococcus neoformans and Cryptococcus gattii, which affects mainly the central nervous system of immunocompromised patients; no reports have been made on the isolation of the fungus from the environment of Popayán, Colombia.

Cryptococcus curvatus O3酵母菌培养及产油脂特性

生物柴油的发展, 导致全球油脂供求紧张。微生物油脂的甘三酯组成与植物油类似, 发展微生物油脂可部分缓解植物油脂供应压力。本文研究了Cryptococcus curvatus O3酵母利用葡萄糖为碳源生长和积累油脂的特性。Cryptococcus curvatus O3酵母在培养过程中能适应间歇式碳源流加方式达到高密度培养的目的, 但在相同培养条件下, 不同氮源能影响其代谢过程中糖到油脂转化的脂肪系数。Cryptococcus curvatus O3酵母利用葡萄糖作为碳源在30°C下摇瓶发酵, 菌体生物量为51.8 g/L, 油脂含量达65.1%。脂肪酸组成分析结果表明, 菌油富含饱和及低度不饱和长链脂肪酸, 其中饱和脂肪酸之和占总脂肪酸组成的64%左右, 其脂肪酸组成类似于可可脂, 这些结果对于利用产油微生物转化生物质获取如类可可脂等具有高附加值油脂的研究具有重要意义。     

Carbonic anhydrase inhibitors. Inhibition of the fungal β-carbonic anhydrases from Candida albicans and Cryptococcus neoformans with boronic acids

Inhibition of the β-carbonic anhydrases (CAs, EC 4.2.1.1) from the pathogenic fungi Cryptococcus neoformans (Can2) and Candida albicans (Nce103) with a series of aromatic, arylalkenyl- and arylalkylboronic acids was investigated. Aromatic, 4-phenylsubstituted- and 2-naphthylboronic acids were the best Can2 inhibitors, with inhibition constants in the range of 8.5–11.5 μM, whereas arylalkenyl and aryalkylboronic acids showed K_Is in the range of 428–3040 μM. Nce103 showed a similar inhibition profile, with the 4-phenylsubstituted- and 2-naphthylboronic acids possessing K_Is in the range of 7.8–42.3 μM, whereas the arylalkenyl and aryalkylboronic acids were weaker inhibitors (K_Is of 412–5210 μM). The host human enzymes CA I and II were also effectively inhibited by these boronic acids. The B(OH)₂ moiety is thus a new zinc-binding group for designing effective inhibitors of the α- and β-CAs.     

Isolation and Characterization of Cryptococcus neoformans Varieties Recovered from Natural Sources in Bogotá, Colombia, and Study of Ecological Conditions in the Area

Cryptococcus neoformans, the etiological agent of cryptococcosis, has been associated with avian droppings and certain trees in different countries, including Colombia. C neoformans environmental isolates were obtained in urban areas in Bogotá, Colombia, and the strains recovered were phenotypically characterized. Attempts to determine the ecological conditions (micro- and macroclimatic) possibly related to their habitat were also undertaken. Four hundred and eighty samples from bark, soil around trunk bases, and detritus inside hollows of 32 trees were collected in three urban areas during a 5-month period, as well as 89 avian droppings samples from different places. Of plant samples, 6.7% collected from nine tree species yielded C. neoformans var. gattii, serotype B strains in 99% of the cases, and C. neoformans var. grubii, serotype A in 1%. The yeast was more frequently recovered from bark than from soil or detritus inside hollows, and from trees with hollows or rotted wood rather than from trees in which birds nest. C. neoformans was present with higher frequency and density in the rainy season than in the dry season; we found that slightly higher temperature and humidity values of the microhabitat, as compared to those of the environment, favored fungal occurrence, but the phenological state of the tree did not. Of dropping samples, 7.9% yielded C. neoformans strains, all of them C. neoformans var. grubii, serotype A. The yeast was obtained more frequently from dry droppings than from moist ones, but neither the sunlight exposure nor the site of collection of samples was correlated with this occurrence. Population density was significantly higher in droppings than in tree samples. Under laboratory conditions, isolates of different serotype showed similar capsular sizes. Water content and pH ranges were wide and did not show any significant difference between positive and negative samples.     

The isolation and characterization of virulence factors of Cryptococcus spp. from saprophytic sources in the city of Ribeirão Preto, São Paulo, Brazil

Yeasts of the Cryptococcus genus are distributed in nature associated to animal and vegetal organic residues. Occasionally, species other than C. neoformans may be responsible for infectious diseases in human and animals. This study aims to determine the occurrence of Cryptococcus species in the atmosphere and bird droppings in the city of Ribeir?o Preto, S?o Paulo, Brazil, and to evaluate three virulence factors: capsule formation, growth at 37 degrees C and melanin production. We analyzed 86 environmental samples (54 droppings and 32 air). Of the 41 strains isolated, 15 were C. neoformans var. neoformans (12 droppings and 3 air), 15 C. albidus (12 droppings and 3 air), 9 C. laurentii (7 droppings and 2 air) and 2 C. uniguttulatus (from droppings). Capsules were produced by 93.3% of C. neoformans var. neoformans, 66.7% of C. albidus, 88.9% of C. laurentii and 50% (1/2) of C. uniguttulatus. All strains of C. neoformans, 20% of C. albidus and 44.4% of C. laurentii were able to grow at 37 degrees C. The melanin production on DOPA agar was verified in C. neoformans (93.3%), C. albidus (26.7%) and C. laurentii (66.7%). We concluded that different Cryptococcus species coexist in the same ecological niche and they are able to produce virulence factors.     

Characterization of Phenotypic Switching in <Emphasis Type="Italic">Cryptococcus neoformans</Emphasis> Biofilms

Cryptococcus neoformans is an encapsulated yeast-like fungus that is a relatively frequent cause of meningoencephalitis in immunocompromised patients and also occasionally causes disease in apparently healthy individuals. This fungus collectively forms biofilms on polystyrene plates and medical devices, whereas individually can undergo phenotypic switching. Both events have profound consequences in the establishment of fungal infection and are associated with persistent infection due to increase resistance to antimicrobial therapy. In this study, we characterized switch phenotypes in C. neoformans biofilms. Smooth, mucoid, and wrinkled switch phenotypes of various switching C. neoformans strains were examined for their adhering and biofilm-forming ability on 96-well plates using cell counts and 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction assay, respectively. Both assays showed that C. neoformans strains with the parent smooth phenotype adhered and formed stronger biofilms than their mucoid and wrinkled counterparts. Furthermore, the phenotypic switching frequencies of the individual colony types grown in biofilms or as planktonic cells were investigated. For the parent smooth variant of most strains, we found enhanced phenotypic switching in cryptococcal biofilms when compared to switching rates of planktonic cells. In contrast, the back-switching rate of mucoid to smooth variant was significantly higher in planktonic cells of seven strains of C. neoformans strains. These results suggested that phenotypic switching can occur in cryptococcal biofilms and extend our understanding of the relationship of both phenomena.