Human Cryptococcosis Research Articles

Growth on Douglas fir media facilitates Cryptococcus virulence factor production and enhances fungal survival against environmental and immune stressors.

The yeasts Cryptococcus neoformans and Cryptococcus gattii are fungal pathogens that can be isolated from the environment, including the surfaces of many plants. Cryptococcus gattii caused an outbreak on Vancouver Island, British Columbia beginning in 1999 that has since spread to the Pacific Northwest of the United States. Coastal Douglas fir (Pseudotsuga menziesii) is an important lumber species and a major component of the ecosystems in this area. Previous research has explored Cryptococcus survival and mating on Douglas fir plants and plant-derived material, but no studies have been done on the production of cryptococcal virulence factors by cells grown on those media. Here, we investigated the effects of growth on Douglas fir-derived media on the production of the polysaccharide capsule and melanin, two of the most important cryptococcal virulence factors. We found that while the capsule was mostly unchanged by growth in Douglas fir media compared to cells grown in defined minimal media, Cryptococcus spp. can use substrates present in Douglas fir to synthesize functional and protective melanin. These results suggest mechanisms by which Cryptococcus species may survive in the environment and emphasize the need to explore how association with Douglas fir trees could affect its epidemiology for human cryptococcosis.

Inbred SJL mice recapitulate human resistance to Cryptococcus infection due to differential immune activation.

Cryptococcosis studies often utilize the common C57BL/6J mouse model. Unfortunately, infection in these mice fails to replicate the basic course of human disease, particularly hampering immunological studies. This work demonstrates that SJL/J mice can recapitulate human infection better than other mouse strains. The immunological response to Cryptococcus infection in SJL/J mice was markedly different from C57BL/6J and much more productive in combating this infection. Characterization of infected mice demonstrated strain-specific genetic linkage and differential regulation of multiple important immune-relevant genes in response to Cryptococcus infection. While our results validate many of the previously identified immunological features of cryptococcosis, we also demonstrate limitations from previous mouse models as they may be less translatable to human disease. We concluded that SJL/J mice more faithfully recapitulate human cryptococcosis serving as an exciting new animal model for immunological and genetic studies.

Molecular typing and antifungal susceptibility of clinical isolates of Cryptococcus neoformans and Cryptococcus gattii species complexes from the National Invasive Fungal Surveillance Network of Uruguay.

Cryptococcus neoformans and C. gattii species complexes (phylum: Basidiomycota) are environmental yeasts and are the main cause of human cryptococcosis worldwide. The most recent molecular typing studies in Latin America have focused on the intertropical region. Thus, this study aimed to update the knowledge of human cryptococcosis in the South American temperate region. We obtained and analyzed 116 C. neoformans/C. gattii species complexes isolates from the Public Health Surveillance Laboratory between 2008-2013 and 2017-2021 (C. gattii species complex=1 and C. neoformans species complex=115). The average patient age was 45 years, with an overall male:female ratio of 3.1:1. The proportion of HIV-negative patients was significantly higher in the second study period. Restriction fragment length polymorphism typing of URA5 gene revealed that the C. neoformans species complex comprised 75.7% VNI, 2.6% VNII, 0.9% VNIII, 1.7% VNIV, 17.4% VNII/VNIV hybrids, and one C. neoformans isolate (0.9%) misidentified as VGI; the C. gattii species complex isolates comprised one VGII. The overall case fatality rate was 49.5%, with no differences in lethality between VNI and hybrid isolates. Of the four isolates responsible for episodes of reoccurrence, only one had a genotype different from the first episode. Antifungal susceptibility testing revealed that most isolates fell below the local epidemiological cut-off value. This study provides additional information for the analysis of C. neoformans/C. gattii species complexes dynamics in the South American temperate region.

Reappraisal of Idiopathic CD4 Lymphocytopenia at 30 Years

BackgroundIdiopathic CD4 lymphocytopenia (ICL) is a clinical syndrome that is defined by CD4 lymphopenia of less than 300 cells per cubic millimeter in the absence of any primary or acquired cause of immunodeficiency. Some 30 years after its original identification, ICL has remained a disease of obscure cause, with limited evidence with respect to its prognosis or management, despite diagnostic and therapeutic innovations.MethodsWe evaluated the clinical, genetic, immunologic, and prognostic characteristics of 108 patients who were enrolled during an 11-year period. We performed whole-exome and targeted gene sequencing to identify genetic causes of lymphopenia. We also performed longitudinal linear mixed-model analyses of T-cell count trajectories and evaluated predictors of clinical events, the response to immunization against coronavirus disease 2019 (Covid-19), and mortality.ResultsAfter the exclusion of patients with genetic and acquired causes of CD4 lymphopenia, the study population included 91 patients with ICL during 374 person-years of follow-up. The median CD4+ T-cell count among the patients was 80 cells per cubic millimeter. The most prevalent opportunistic infections were diseases related to human papillomavirus (in 29%), cryptococcosis (in 24%), molluscum contagiosum (in 9%), and nontuberculous mycobacterial diseases (in 5%). A reduced CD4 count (<100 cells per cubic millimeter), as compared with a CD4 count of 101 to 300 cells, was associated with a higher risk of opportunistic infection (odds ratio, 5.3; 95% confidence interval [CI], 2.8 to 10.7) and invasive cancer (odds ratio, 2.1; 95% CI, 1.1 to 4.3) and a lower risk of autoimmunity (odds ratio, 0.5; 95% CI, 0.2 to 0.9). The risk of death was similar to that in the age- and sex-adjusted general population, but the prevalence of cancer was higher.ConclusionsAmong the study patients, ICL continued to be associated with increased susceptibility to viral, encapsulated fungal, and mycobacterial diseases, as well as with a reduced response to novel antigens and an increased risk of cancer. (Funded by the National Institute of Allergy and Infectious Diseases and the National Cancer Institute; ClinicalTrials.gov number, NCT00867269.)

Recent Advances in the Ecoepidemiology, Virulence and Diagnosis of Cryptococcus Neoformans and Cryptococcus Gattii Species Complexes

Emerging environmental pathogenic fungal infections, including cryptococcosis, continue to pose a significant threat to humans with compromised immunity and, to some extent, healthy ones. Cryptococcus neoformans was originally identified as the main etiological agent of human cryptococcosis, but recent studies have also identified the occurrence of opportunistic infections caused by Cryptococcus gattii. These two saprophytic facultative yeasts present a paradox as they can infect humans without requiring a host for replication or survival, a phenomenon termed readymade virulence. Many cryptococcal virulence traits appear to have dual effects that provide survival advantages in both animal hosts and the environment. Several molecular techniques have been developed to provide in-depth knowledge of these species complexes. This review will focus on the description of the Cryptococcus neoformans and Cryptococcus gattii (CnCg) species complexes and associated cryptococcal pathogenesis, ecological niches, and virulence factors employed by the pathogens to cause disease.

Development of a Heat-Killed fbp1 Mutant Strain as a Therapeutic Agent To Treat Invasive Cryptococcus Infection.

In previous studies, we determined that the F-box protein Fbp1, a subunit of the SCF(Fbp1) E3 ligase in Cryptococcus neoformans, is essential for fungal pathogenesis. Heat-killed fbp1Δ cells (HK-fbp1) can confer vaccine-induced immunity against lethal challenge with clinically important invasive fungal pathogens, e.g., C. neoformans, C. gattii, and Aspergillus fumigatus. In this study, we found that either CD4+ T cells or CD8+ T cells were sufficient to confer protection against lethal challenge by C. neoformans in HK-fbp1-induced immunity. Given the potent effect of HK-fbp1 as a preventative vaccine, we further tested the potential efficacy of administering HK-fbp1 cells as a therapeutic agent for treating animals after infection. Remarkably, administration of HK-fbp1 provided robust host protection against preexisting C. neoformans infection. The mice infected with wild-type H99 cells and then treated with HK-fbp1 showed significant reduction of fungal burden in the infected lung and no dissemination of fungal cells to the brain and spleen. We find that early treatment is critical for the effective use of HK-fbp1 as a therapeutic agent. Immune analysis revealed that early treatment with HK-fbp1 cells elicited Th1-biased protective immune responses that help block fungal dissemination and promote better host protection. Our data thus suggest that HK-fbp1 is both an effective prophylactic vaccine candidate against C. neoformans infection in both immunocompetent and immunocompromised populations and a potential novel therapeutic strategy to treat early-stage cryptococcosis. IMPORTANCE Invasive fungal infections, e.g., cryptococcosis, are often life threatening and difficult to treat with very limited therapeutic options. There is no vaccine available in clinical use to prevent or treat fungal infections. Our previous studies demonstrated that heat-killed fbp1Δ cells (HK-fbp1) in Cryptococcus neoformans can be harnessed to confer protection against a challenge by the virulent parental strain, even in immunocompromised animals, such as ones lacking CD4+ T cells. In this study, we further determined that T cells are required for vaccine-induced protection against homologous challenge and that either CD4+ or CD8+ cells are sufficient. This finding is particularly important for the potential utility of this vaccine candidate in the context of HIV/AIDS-induced immune deficiency, the main risk factor for cryptococcosis in humans. Furthermore, in addition to the utility of HK-fbp1 as a prophylactic vaccine, we found that HK-fbp1 administration can inhibit disease dissemination when animals are treated at an early stage during Cryptococcus infection. Our findings could significantly expand the utility of HK-fbp1 not only as a prophylactic vaccine but also as a novel therapy against cryptococcosis. In all, our studies showed that the HK-fbp1 strain can be used both preventively and therapeutically to elicit robust host protection against cryptococcosis.

Off-label treatments as potential accelerators in the search for the ideal antifungal treatment of cryptococcosis.

Cryptococcosis is an opportunistic mycosis that mainly affects immunosuppressed patients. The treatment is a combination of three antifungal agents: amphotericin B, 5-flucytosine and fluconazole. However, these drugs have many disadvantages, such as high nephrotoxicity, marketing bans in some countries and fungal resistance. One of the solutions to find possible new drugs ispharmacological repositioning. This work presents repositioned drugs as an alternative for new antifungal therapies for cryptococcosis. All the studies here were performed in vitro or in animal models, except for sertraline, which reached phase III in humans. There is still no pharmacological repositioning approval for cryptococcosis in humans, though this review shows the potential of repurposing as a rapid approach to finding new agents to treat cryptococcosis.

The Cryptococcus gattii species complex: Unique pathogenic yeasts with understudied virulence mechanisms.

Members of Cryptococcus gattii/neoformans species complex are the etiological agents of the potentially fatal human fungal infection cryptococcosis. C. gattii and its sister species cause disease in both immunocompetent and immunocompromised hosts, while the closely related species C. neoformans and C. deneoformans predominantly infect immunocompromised hosts. To date, most studies have focused on similarities in pathogenesis between these two groups, but over recent years, important differences have become apparent. In this review paper, we highlight some of the major phenotypic differences between the C. gattii and neoformans species complexes and justify the need to study the virulence and pathogenicity of the C. gattii species complex as a distinct cryptococcal group.

Antifungal susceptibility of the clinical and environmental strains of Cryptococcus gattii sensu lato in Taiwan.

The rare occurrence of human cryptococcosis caused by Cryptococcus gattii sensu lato leads to difficulties in establishing the antifungal susceptibility profile between species of this potentially lethal pathogen, which may be crucial for treating cryptococcosis. To establish an antifungal susceptibility profile of C. gattii s.l. in Taiwan. A total of 104 environmental C. gattii s.l. strains (including multilocal sequence typing ST7, ST106, ST274, ST328, ST546, ST548 and ST630) and 21 previously collected clinical strains (including ST7, ST44, ST06, ST274, ST328 and ST329) were included in this study. We determined the minimum inhibitory concentrations (MICs) of six antifungal agents (itraconazole, fluconazole, voriconazole, posaconazole, flucytosine and amphotericin B) against environmental C. gattii s.l. strains and compared the antifungal susceptibility profiles of environmental strains with those of clinical strains. The antifungal susceptibility data demonstrated that the MICs of antifungal agents against environmental strains were comparable to those against clinical strains. Compared with strains of Cryptococcus deuterogattii, those of C. gattii sensu stricto were more susceptible to azoles and flucytosine. The differences in antifungal susceptibility between the strains of each sequence type (ST) were significant. Correlation analysis of MICs revealed cross-resistance between azoles in environmental strains of C. gattii s.l. Geographic differences in the antifungal susceptibility of C. gattii s.l. isolated from different cities in Taiwan were observed in this study. Clinical and environmental strains were indistinguishable in antifungal susceptibility. The antifungal susceptibility of C. gattii s.l. is associated with STs. Therefore, establishing an ST-oriented domestic antifungal susceptibility database may help treat C. gattii s.l.-induced cryptococcosis.

Randomized, phase 1/2, double-blind pioglitazone repositioning trial combined with antifungals for the treatment of cryptococcal meningitis – PIO study

BackgroundCryptococcosis affects more than 220,000 patients/year, with high mortality even when the standard treatment [amphotericin B (AMB), 5-flucytosin (5-FC) and fluconazole] is used. AMB presents high toxicity and 5-FC is not currently available in Brazil. In a pre-clinical study, pioglitazone (PIO - an antidiabetic drug) decreased AMB toxicity and lead to an increased mice survival, reduced morbidity and fungal burden in brain and lungs. The aim of this trial is to evaluate the efficacy and safety of PIO combined with standard antifungal treatment for human cryptococcosis. MethodsA phase 1/2, randomized, double blind, placebo-controlled trial will be performed with patients from Belo Horizonte, Brazil. They will be divided into three groups (placebo, PIO 15 mg/day or PIO 45 mg/day) and will receive an additional pill during the induction phase of cryptococcosis’ treatment. Our hypothesis is that treated patients will have increased survival, so the primary outcome will be the mortality rate. Patients will be monitored for survival, side effects, fungal burden and inflammatory mediators in blood and cerebrospinal fluid. The follow up will occur for up 60 days. ConclusionsWe expect that PIO will be an adequate adjuvant to the standard cryptococcosis’ treatment. Trial registrationICTRP/WHO (and International Clinical Trial Registry Plataform (ICTRP/WHO) (http://apps.who.int/trialsearch/Trial2.aspx?TrialID=RBR-9fv3f4), RBR-9fv3f4 (http://www.ensaiosclinicos.gov.br/rg/RBR-9fv3f4). UTN Number: U1111-1226-1535. Ethical approvement number: CAAE 17377019.0.0000.5149.

Cytotoxicity and Antimicrobial Properties of Photosynthesized Silver Chloride Nanoparticles Using Plant Extract from Stryphnodendron adstringens (Martius) Coville

Stryphnodendron adstringens (Martius) Coville is a medicinal plant described as having pharmacological properties as anti-inflammatory and antimicrobial activities. Silver chloride nanoparticles (AgCl-NPs) have shown great potential for biomedical applications with efficient antimicrobial properties. Here, we report the photosynthesis of AgCl-NPs using plant extract from S. adstringens (SaAgCl-NPs) and their cytotoxic and antimicrobial activities. We photosynthesized SaAgCl-NPs nearly spherical with low heterogeneity in size and enveloped by an organic material layer responsible for colloidal stability. SaAgCl-NPs was non-cytotoxic against mammalian VERO cells; however, SaAgCl-NPs presented remarkable antifungal activity against the pathogenic yeast Cryptococcus neoformans (MIC80 of 0.32 µg/mL) the causative agent of human cryptococcosis. Notable antibacterial activity was observed against Gram-negative bacteria Pseudomonas aeruginosa (MIC80 of 2.56 µg/mL) e Serratia marcescens (MIC80 of 20.48 µg/mL) both microorganisms associated with a variety of human infections, in particular pneumonia. In contrast, Gram-positive bacteria Staphylococcus aureus and Staphylococcus epidermidis, microorganisms that cause pathologies as skin infections, were less susceptible to the SaAgCl-NPs both with MIC80 of 40.93 µg/mL. Thus, SaAgCl-NPs represents an organic–inorganic hybrid nanomaterial with very low cytotoxicity against mammalian cells and high antimicrobial efficiency against pathogenic microorganisms and may be explored as an alternative to antimicrobial drugs.

Peritoneal Cryptococcosis in a Dog

Background: Cryptococcosis is an opportunistic, systemic mycotic disease caused by a yeast of Cryptococcus neoformans. These pathogens cause serious public health problems, as they can be transmitted to humans, domestic and wild animals. In cats and dogs, the main site of infection is the upper lower respiratory tract, however, the infection can extend and affect other sites in the organism, however, the peritoneal manifestation of the disease is rare. Thus, the present work aims to report a case of cryptococcosis in a canine, mixed breed, female, adult, from the Metropolitan Region of Belém.Case: A mixed breed dog, female, adult was admitted in a veterinary hospital at Belém, presenting abdominal discomfort and, after the clinical examination, emergency exploratory laparotomy was indicated, and it were observed disseminated lesions in the abdominal cavity, with multiple nodules attached to the peritoneum and intestinal serosa and bladder, uterus, among other organs. Fragments from the surgical biopsy were fixed, and processed routinely according to the techniques for histological tissue processing. Histological examination revealed a predominance of granulomatous lesions in peritoneum and mesentery organs. It was observed a discrete inflammatory reaction of macrophages, epithelioid cells and giant cells, many in phagocytosis of spherical or ovoid organisms, with a thick capsule and a clear perinuclear halo. In the PAS staining, the Cryptococcus conidia presented eosinophilic characteristics and some of them had the capsule well demarcated, which was shown to be radiated. Also it was possible to see the budding yeast and in the Grocott stain, the Cryptococcus stained in black.Discussion: Cryptococcosis with peritoneal involvement in animals is rarely reported in the literature. Cryptococcus is an agent that presents tropism by the central nervous system and nasal cavity, however atypical presentations have been reported, especially at the level of the abdominal cavity (intestines and mesentery). It is believed that the gastrointestinal tract is the gateway for ascending contamination, or that the contamination can occur by fungal ingestion. The lesions presented a multiple distribution, with isolated and coalescent nodules adhered to the peritoneum and adjacent structures. The literature reports two cases of dogs with intra-abdominal cryptococcosis, in which, macroscopically, granulomatous formations were observed in the jejunum, with lymph nodes and mesentery. Microscopically, a discrete inflammatory infiltrate of macrophages and lymphocytes were observed. Some areas with granulomatous reaction, lymphocytes, epithelioid macrophages and giant cells and, in other areas, yeasts in the cytoplasm were observed. The yeasts were spherical or ovoid, surrounded by a thick capsule of polysaccharide. The periodic acid Schiff (PAS) and silver impregnation (Grocott) staining were used to highlight structures of the Cryptococcus wall which were presented by a strong stained polysaccharide capsule. It must be emphasized the zoonotic potential of cryptococcosis, a disease that can affect both animals and humans. Cryptococcosis in humans normally occurs when the fungus accesses the airways through inhalation and ranges from asymptomatic pulmonary colonization to compromised meninges, causing the human patient's life-threatening condition. In the present report, the diagnosis of cryptococcosis was established through histopathological and histochemical examination of the fungal structure, which were determinant in the etiological diagnosis of cryptococcosis.

Microbe Profile: Cryptococcus neoformans species complex.

Cryptococcus neoformans is a lethal fungus disguised in a polysaccharide coat. It can remain dormant in the host for decades prior to reactivation, causing systemic cryptococcosis in humans and other mammals. Cryptococcus deploys a multitude of traits to adapt to and survive within the host, including immunosuppression, an ability to replicate intra- and extra-cellularly in phagocytes, changes in morphology and ploidy, a predilection to infect the CNS, and the capacity to utilize neurotransmitters and unique carbon sources available in the brain. These pathogenic strategies displayed by this fungus might have evolved through its interactions with microbial predators in the environment.

A novel method for identifying and distinguishing Cryptococcus neoformans and Cryptococcus gattii by surface-enhanced Raman scattering using positively charged silver nanoparticles

There are approximately 1 million cryptococcal infections per year among HIV+ individuals, resulting in nearly 625,000 deaths. Cryptococcus neoformans and Cryptococcus gattii are the two most common species that cause human cryptococcosis. These two species of Cryptococcus have differences in pathogenicity, diagnosis, and treatment. Cryptococcal infections are usually difficult to identify because of their slow growth in vitro. In addition, the long detection cycle of Cryptococcus in clinical specimens makes the diagnosis of Cryptococcal infections difficult. Here, we used positively charged silver nanoparticles (AgNPs+) as a substrate to distinguish between C. neoformans and C. gattii in clinical specimens directly via surface-enhanced Raman scattering (SERS) and spectral analysis. The AgNPs+ self-assembled on the surface of the fungal cell wall via electrostatic aggregation, leading to enhanced SERS signals that were better than the standard substrate negatively charged silver nanoparticles (AgNPs). The SERS spectra could also be used as a sample database in the multivariate analysis via orthogonal partial least-squares discriminant analysis. This novel SERS detection method can clearly distinguish between the two Cryptococcus species using principal component analysis. The accuracy of the training data and test data was 100% after a tenfold crossover validation.

Polysaccharide diversity in VNI isolates of Cryptococcus neoformans from Roraima, Northern Brazil

Species of the Cryptococcus genus comprise environmental, encapsulated fungal pathogens that cause lethal meningitis in immunosuppressed individuals. In humans, fungal uptake of hypocapsular Cryptococcus by macrophages was associated with high fungal burden in the cerebrospinal fluid and long-term patient survival. On the basis of the key role of the cryptococcal capsule in disease, we analyzed the diversity of capsular structures in 23 isolates from pigeon excreta collected in the cities of Boa Vista, Bonfim and Pacaraima, in the state of Roraima (Northern Brazil). All isolates were identified as Cryptococcus neoformans (VNI genotype) by MALDI-TOF mass spectrometry. Through a combination of fluorescence microscopy, flow cytometry, ELISA and spectrophotometric methods, each isolate was characterized at the phenotypical level, which included measurements of growth rates at 30 and 37 °C, pigmentation, cell body size, capsular dimensions, serological reactivity, urease production and ability to produce extracellular glucuronoxylomannan (GXM), the main capsular component of C. neoformans. With the exception of melanization, a formidable diversity was observed considering all parameters tested in our study. Of note, hyper and hypo producers of GXM were identified, in addition to isolates with hyper and hypo profiles of reactivity with a polysaccharide-binding monoclonal antibody. Capsular dimensions were also highly variable in the collection of isolates. Extracellular GXM production correlated positively with capsular dimensions, urease activity and cell size. Unexpectedly, GXM concentrations did not correlate with serological reactivity with the cryptococcal capsule. These results reveal a high diversity in the ability of environmental C. neoformans to produce capsular components, which might impact the outcome of human cryptococcosis.

Effect of non-antifungal agrochemicals on the pathogenic fungus Cryptococcus gattii.

The chemical control of pests and weeds is employed to improve crop production and the quality of agricultural products. The intensive use of pesticides, however, may cause environmental contamination, thus altering microbial communities. Cryptococcus gattii is an environmental yeast and the causative agent of cryptococcosis in both humans and animals. Up to this day, the effects of agrochemicals on human pathogens living in nature are still widely unknown. In this work, we analyzed the susceptibility of C. gattii to nonfungicide agrochemicals (herbicides and insecticides). Microdilution and drug-combination susceptibility tests were performed for the herbicides flumioxazin (FLX), glyphosate (GLY), isoxaflutole (ISO), pendimethalin (PEND), and also for the insecticide fipronil (FIP). Moreover, these compounds were combined with the clinical antifungals amphotericin B and fluconazole. The MIC values found for the agrochemicals were the following: < 16μg/ml, for flumioxazin; 128 to 256μg/ml, for FIP, ISO, and PEND; and >256μg/ml, for GLY. Synergistic and antagonistic interactions, depending on the strain and concentration tested, were also observed. All strains had undergone adaptation to increasing levels of agrochemicals, in order to select the less susceptible subpopulations. During this process, one C. gattii strain (196L/03) tolerated high concentrations (50 to 900μg/ml) of all pesticides assessed. Subsequently, the strain adapted to flumioxazin, isoxaflutole and pendimethalin showed a reduction in the susceptibility to agrochemicals and clinical antifungals, suggesting the occurrence of cross-resistance. Our data point to the risk of exposing C. gattii to agrochemicals existing in the environment, once it might impact the susceptibility of clinical antifungals.

The Buoyancy of Cryptococcus neoformans Is Affected by Capsule Size.

Cryptococcus neoformans is an environmental pathogenic fungus with a worldwide geographical distribution that is responsible for hundreds of thousands of human cryptococcosis cases each year. During infection, the yeast undergoes a morphological transformation involving capsular enlargement that increases microbial volume. To understand the factors that play a role in environmental dispersal of C. neoformans and C. gattii, we evaluated the cell density of Cryptococcus using Percoll isopycnic gradients. We found differences in the cell densities of strains belonging to C. neoformans and C. gattii species complexes. The buoyancy of C. neoformans strains varied depending on growth medium. In minimal medium, the cryptococcal capsule made a major contribution to the cell density such that cells with larger capsules had lower density than those with smaller capsules. Removing the capsule, by chemical or mechanical methods, increased the C. neoformans cell density and reduced buoyancy. Melanization of the C. neoformans cell wall, which also contributes to virulence, produced a small but consistent increase in cell density. Encapsulated C. neoformans sedimented much more slowly in seawater as its density approached the density of water. Our results suggest a new function for the capsule whereby it can function as a flotation device to facilitate transport and dispersion in aqueous fluids.IMPORTANCE The buoyancy of a microbial cell is an important physical characteristic that may affect its transportability in fluids and interactions with tissues during infection. The polysaccharide capsule surrounding C. neoformans is required for infection and dissemination in the host. Our results indicate that the capsule has a significant effect on reducing cryptococcal cell density, altering its sedimentation in seawater. Modulation of microbial cell density via encapsulation may facilitate dispersal for other important encapsulated pathogens.

Undiagnosed Cryptococcus gattii meningitis leading to subsequent ventriculoperitoneal shunt infection in a patient with symptoms of normal pressure hydrocephalus: case report and literature review

BackgroundCryptococcus gattii is known to be an etiologic agent of human cryptococcosis, particularly in immunocompetent persons. C. gattii infection usually involves the central nervous system, the respiratory tract, or may be disseminated. Here we report an atypical manifestation of C. gattii infection in a patient who had C. gattii meningitis complicating the ventriculoperitoneal (VP) shunt infection and concurrent infected intraabdominal VP shunt pseudocyst.Case presentationA 66-year-old Thai female was initially diagnosed with normal pressure hydrocephalus (NPH) and underwent programmable VP shunt placement. However, she still suffered from recurrent communicating hydrocephalus with in-place VP shunt, and later developed recurrent gait impairment, chronic abdominal pain and abdominal mass. Radiological studies demonstrated recurrent hydrocephalus and a very large intraabdominal VP shunt pseudocyst. C. gattii was isolated from both the cerebrospinal fluid and the pseudocyst aspiration. C. gattii meningitis complicating the VP shunt infection and concurrent infected intraabdominal VP shunt pseudocyst was diagnosed. Prolonged antifungal therapy, removal of the infected VP shunt with subsequent implant of a new shunt provided a good outcome.ConclusionChronic C. gattii meningitis should be aware in a patient presenting with normal pressure hydrocephalus. Under-diagnosed cryptococcal meningitis following VP shunt insertion for treating the hydrocephalus can render a complicated VP shunt infection including infected VP shunt pseudocyst.

The Overlooked Glycan Components of the Cryptococcus Capsule.

Pathogenic species of Cryptococcus kill approximately 200,000 people each year. The most important virulence mechanism of C. neoformans and C. gattii, the causative agents of human and animal cryptococcosis, is the ability to form a polysaccharide capsule. Acapsular mutants of C. neoformans are avirulent in mice models of infection, and extracellularly released capsular polysaccharides are deleterious to the immune system. The principal capsular component in the Cryptococcus genus is a complex mannan substituted with xylosyl and glucuronyl units, namely glucuronoxylomannan (GXM). The second most abundant component of the cryptococcal capsule is a galactan with multiple glucuronyl, xylosyl, and mannosyl substitutions, namely glucuronoxylomannogalactan (GXMGal). The literature about the structure and functions of these two polysaccharides is rich, and a number of comprehensive reviews on this topic are available. Here, we focus our discussion on the less explored glycan components associated with the cryptococcal capsule, including mannoproteins and chitin-derived molecules. These glycans were selected for discussion on the basis that i) they have been consistently detected not only in the cell wall but also within the cryptococcal capsular network and ii) they have functions that impact immunological and/or pathogenic mechanisms in the Cryptococcus genus. The reported functions of these molecules strongly indicate that the biological roles of the cryptococcal capsule go far beyond the well-known properties of GXM and GXMGal.

Antibody and B Cell Subset Perturbations in Human Immunodeficiency Virus-Uninfected Patients With Cryptococcosis.

The importance of antibody immunity in protection against Cryptococcus neoformans remains unresolved. We measured serum C neoformans-specific and total antibody levels and peripheral blood B cell subsets of 12 previously healthy patients with cryptococcosis (cases) and 21 controls. Before and after adjustment for age, sex, and race, cryptococcal capsular polysaccharide immunoglobulin G was higher in cases than controls, whereas total B and memory B cell levels were lower. These associations parallel previous findings in patients with human immunodeficiency virus-associated cryptococcosis and suggest that B cell subset perturbations may also associate with disease in previously normal individuals with cryptococcosis.