The Outbreak of Cryptococcus gattii in Western North America: Epidemiology and Clinical Issues

Disseminated Cryptococcus over pancreas, lung, and brain: a case report

BACKGROUND

Cryptococcus is an opportunistic infection acquired through inhalation from the environment, primarily affecting individuals with compromised immune systems. It typically leads to pneumonia upon passing through lung tissue. The infection can disseminate to various organs via the bloodstream, resulting in meningitis or encephalitis in the central nervous system. Disseminated Cryptococcus has been reported to involve the skin, liver, eyes, lymph nodes, bone marrow, spleen, kidneys, and intestines, significantly increasing morbidity and mortality. However, pancreatic involvement in Cryptococcus is relatively rare, and a few case reports have highlighted severe organ damage and high mortality rates.

CASE PRESENTATION

In this case report, we present the case of a 36-year-old Asian man who presented with a 2-week history of headaches and blurred vision in his right eye. Brain magnetic resonance imaging revealed multiple brain masses, along with a mass in the lower left lung field and a tumor in the pancreatic tail, as detected by chest computed tomography. Endoscopic ultrasound-guided fine needle biopsy and computed tomography-guided lung biopsy confirmed the diagnosis of disseminated cryptococcal infection involving the pancreas, lung, and brain. The patient's clinical condition improved following antifungal therapy. Additionally, we identified anti-granulocyte-macrophage colony-stimulating factor antibody as a risk factor for disseminated cryptococcal infection in this patient.

CONCLUSION

Disseminated cryptococcosis can be a potentially lethal condition, as highlighted by previous literature. However, early diagnosis using contrast-enhanced harmonic endoscopic ultrasound and endoscopic ultrasound-guided biopsies, as well as prompt treatment as demonstrated in our case, can improve outcomes and prevent mortality.

Pregnancy-related intracranial venous sinus thrombosis secondary to cryptococcal meningoencephalitis: a case report and literature review

BACKGROUND

Cerebral venous sinus thrombosis (CVST), a serious cerebrovascular and neurological emergency, is common in pregnant individuals and accounts for approximately 0.5-1.0% of all cerebrovascular diseases. However, CVST with cryptococcal meningoencephalitis in immunocompetent pregnant patients is rare.

CASE PRESENTATION

A 30-year-old woman who was 33 weeks pregnant presented with recurrent dizziness, headache, and vomiting as the main clinical manifestations, all of which were initially nonspecific. After assessment of the cerebrospinal fluid, skull computerized tomography, magnetic resonance imaging, and other laboratory and imaging examinations, the patient was diagnosed with secondary pregnancy-related CVST with cryptococcal meningoencephalitis. Despite receiving potent anticoagulant and antifungal treatment, the patient's condition deteriorated, and the patient's family opted to cease treatment.

CONCLUSIONS

We present a rare case of CVST with cryptococcal meningoencephalitis in an immunocompetent pregnant patient. The difficulty of diagnosing and treating secondary pregnancy-related CVST caused by cryptococcal meningoencephalitis, as well as the great challenges faced at present are highlighted. One crucial lesson from the present case is that when clinical and imaging signs are unusual for CVST during pregnancy, it is essential to account for the possibility of other central nervous system (CNS) diseases, such as CNS infections with Cryptococcus, which may cause CVST.

Influence of the agrochemical benomyl on Cryptococcus gattii-plant interaction in vitro and in vivo

Cryptococcus gattii, an environmental fungus, is one of the agents of cryptococcosis. The influence of agrochemicals on fungal resistance to antifungals is widely discussed. However, the effects of benomyl (BEN) on fungal interaction with different hosts is still to be understood. Here we studied the influence of adaptation to BEN in the interaction with a plant model, phagocytes and with Tenebrio molitor. First, the strain C. gattii L24/01 non-adapted (NA), adapted (A) to BEN, and adapted with further culture on drug-free media (10p) interact with Nicotiana benthamiana, with a peak in the yeast burden on the 7th day post-inoculation. C. gattii L24/01 A and 10p provided lower fungal burden, but these strains increased cell diameter and capsular thickness after the interaction, together with decreased fungal growth. The strains NA and A showed reduced ergosterol levels, while 10p exhibited increased activity of laccase and urease. L24/01 A recovered from N. benthamiana was less engulfed by murine macrophages, with lower production of reactive oxygen species. This phenotype was accompanied by increased ability of this strain to grow inside macrophages. Otherwise, L24/01 A showed reduced virulence in the T. molitor larvae model. Here, we demonstrate that the exposure to BEN, and interaction with plants interfere in the morphophysiology and virulence of the C. gattii.

Genotypic Diversity and Antifungal Susceptibility of Clinical Isolates of Cryptococcus Gattii Species Complex from Argentina

The aim of this study was to determine the genotypic diversity of 22 Cryptococcus gattii species complex clinical isolates from Argentina and to place these genotypes within the diversity of clinical, veterinary and environmental isolates from Latin America. Mating type and antifungal susceptibility of the isolates were also determined. By URA5-RFLP, nine isolates were identified as molecular type VGI, 10 as VGII, one as VGIII and two as VGIV. Multilocus sequence typing (MSLT), following the International Society for Human and Animal Mycology (ISHAM) consensus MLST scheme, was used to determine the genotypic diversity. Our results suggest that, in Argentina, VGI isolates have low genetic diversity, while VGII isolates have high genetic diversity. Both isolates identified as VGIV by URA5-RFLP were genotyped by MLST as belonging to the currently named VGVI clade. From all isolates, eight sequence types (STs) were unique for Argentina, while five STs have been reported already in other countries, being of high interest the genotypes ST20 and ST7 since they belong to the subtypes VGIIa and VGIIb, respectively, which are associated with hypervirulent strains responsible for outbreaks in North America. To note, geographical analysis showed that some genotypes may be associated with some regions in Argentina. Most isolates were MATα, but we are reporting one isolate MATa for the first time in the country. Antifungal susceptibility tests showed that itraconazole, voriconazole and posaconazole had high activity against all isolates, while amphotericin B, fluconazole and 5-fluorocytosine were the least active drugs against all studied isolates.

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.

Treatment of Cryptococcal Meningitis: How Have We Got Here and Where are We Going?

Cryptococcal meningitis is a devastating brain infection cause by encapsulated yeasts of the Cryptococcus genus. Exposure, through inhalation, is likely universal by adulthood, but symptomatic infection only occurs in a minority, in most cases, months or years after exposure. Disease has been described in almost all tissues, but it is the organism’s tropism for the central nervous system that results in the most devastating illness. While invasive disease can occur in the immunocompetent, the greatest burden by far is in immunocompromised individuals, particularly people living with human immunodeficiency virus (HIV), organ transplant recipients and those on glucocorticoid therapy or other immunosuppressive drugs. Clinical presentation is variable, but diagnosis is usually straightforward, with cerebrospinal fluid microscopy, culture, and antigen testing proving significantly more sensitive than diagnostic tests for other brain infections. Although disease incidence has reduced since the advent of effective HIV therapy, mortality when disease occurs remains extremely high, and has changed little in recent decades. This Therapy in Practice review is an update of a talk first given by JND at the European Congress on Clinical Microbiology and Infectious Diseases in 2019 in the Netherlands. The review contextualizes the most recently published World Health Organization (WHO) guidelines for the treatment of HIV-associated cryptococcal meningitis in terms of the data from large, randomized, controlled trials published between 1997 and 2022. We discuss the rationale for induction and maintenance therapy and the efficacy and undesirable effects of the current therapeutic armamentarium of amphotericin, flucytosine and fluconazole. We address recent research into repurposed drugs such as sertraline and tamoxifen, and potential future treatment options, including the novel antifungals fosmanogepix, efungumab and oteseconazole, and non-pharmaceutical solutions such as neurapheresis cerebrospinal fluid filtration.

The need for environmental surveillance to understand the ecology, epidemiology and impact of Cryptococcus infection in Africa

Our understanding of the pathogenic yeasts Cryptococcus neoformans and Cryptococcus gattii has been greatly enhanced by use of genome sequencing technologies. Found ubiquitously as saprotrophs in the environment, inhalation of infectious spores from these pathogens can lead to the disease cryptococcosis. Individuals with compromised immune systems are at particular risk, most notably those living with HIV/AIDS. Genome sequencing in combination with laboratory and clinical studies has revealed diverse lineages with important differences in their observed frequency, virulence and clinical outcomes. However, to date, genomic analyses have focused primarily on clinical isolates that represent only a subset of the diversity in the environment. Enhanced genomic surveillance of these yeasts in their native environments is needed in order to understand their ecology, biology and evolution and how these influence the epidemiology and pathophysiology of clinical disease. This is particularly relevant on the African continent from where global cryptococcal diversity may have originated, yet where environmental sampling and sequencing has been sparse despite harbouring the largest population at risk from cryptococcosis. Here, we review what scientifically and clinically relevant insights have been provided by analysis of environmental Cryptococcus isolates to date and argue that with further sampling, particularly in Africa, many more important discoveries await.

Global warming impact on the expansion of fundamental niche of Cryptococcus gattii VGI in Europe

In the present study, we analysed how geographical distribution of the fungal pathogen Cryptococcus gattii VGI in Europe and Mediterranean area has evolved in the last four decades based on the climatic changes, and we tried to predict the scenario for the next decade. Niche modelling by Maxent analysis showed that recent climate changes have significantly affected the distribution of the fungus revealing a gradual expansion of the fundamental niche from 1980 to 2009 followed by an impressive increase in the last decade (2010-2019) during which the environmental surface suitable for the fungal survival was more than doubled. In the next decade, our model predicted an increase in the area of distribution of C. gattii VGI from the coasts of the Mediterranean basin towards the more internal sub-continental areas. On the basis of these predictions, an increase of cases of cryptococcosis due to C. gattii VGI is expected in the next decade and a constant monitoring of the epidemiology of this fungal pathogen represents a crucial strategy to detect the onset of future outbreaks.

Pleiotropy and epistasis within and between signaling pathways defines the genetic architecture of fungal virulence

Cryptococcal disease is estimated to affect nearly a quarter of a million people annually. Environmental isolates of Cryptococcus deneoformans, which make up 15 to 30% of clinical infections in temperate climates such as Europe, vary in their pathogenicity, ranging from benign to hyper-virulent. Key traits that contribute to virulence, such as the production of the pigment melanin, an extracellular polysaccharide capsule, and the ability to grow at human body temperature have been identified, yet little is known about the genetic basis of variation in such traits. Here we investigate the genetic basis of melanization, capsule size, thermal tolerance, oxidative stress resistance, and antifungal drug sensitivity using quantitative trait locus (QTL) mapping in progeny derived from a cross between two divergent C. deneoformans strains. Using a "function-valued" QTL analysis framework that exploits both time-series information and growth differences across multiple environments, we identified QTL for each of these virulence traits and drug susceptibility. For three QTL we identified the underlying genes and nucleotide differences that govern variation in virulence traits. One of these genes, RIC8, which encodes a regulator of cAMP-PKA signaling, contributes to variation in four virulence traits: melanization, capsule size, thermal tolerance, and resistance to oxidative stress. Two major effect QTL for amphotericin B resistance map to the genes SSK1 and SSK2, which encode key components of the HOG pathway, a fungal-specific signal transduction network that orchestrates cellular responses to osmotic and other stresses. We also discovered complex epistatic interactions within and between genes in the HOG and cAMP-PKA pathways that regulate antifungal drug resistance and resistance to oxidative stress. Our findings advance the understanding of virulence traits among diverse lineages of Cryptococcus, and highlight the role of genetic variation in key stress-responsive signaling pathways as a major contributor to phenotypic variation.

Diverse species in the genus Cryptococcus: Pathogens and their non-pathogenic ancestors

The genus Cryptococcus comprises of more than 30 species. It consists of clinically significant pathogenic Cryptococcus neoformans/Cryptococcus gattii species complex comprising of a minimum of seven species. These pathogens cost more than 200,000 lives annually by causing cryptococcal meningoencephalitis. The evolution of the pathogenic species from closely related non-pathogenic species of the Cryptococcus amylolentus complex is of particular importance and several advances have been made to understand their phylogenetic and genomic relationships. The current review briefly describes the sexual reproduction process followed by an individual description of the members focusing on their key attributes and virulence mechanisms of the pathogenic species. A special section on phylogenetic studies is aimed at understanding the evolutionary divergence of pathogens from non-pathogens. Recent findings from our group pertaining to parameters affecting codon usage bias in six pathogenic and three non-pathogenic ancestral species and their corroboration with existing phylogenetic reports are also included in the current review.

Expansion of the Emerging Fungal Pathogen Cryptococcus bacillisporus Into America: Linking Phylogenetic Origin, Geographical Spread and Population Under Exposure Risk

In 2018 the fungal pathogen Cryptococcus bacillisporus (AFLP5/VGIII) was isolated for the first time in Chile, representing the only report in a temperate region in South America. We reconstructed the colonization process of C. bacillisporus in Chile, estimating the phylogenetic origin, the potential spread zone, and the population at risk. We performed a phylogenetic analysis of the strain and modeled the environmental niche of the pathogen projecting its potential spread zone into the new colonized region. Finally, we generated risk maps and quantified the people under potential risk. Phylogenetic analysis showed high similarity between the Chilean isolate and two clonal clusters from California, United States and Colombia in South America. The pathogen can expand into all the temperate Mediterranean zone in central Chile and western Argentina, exposing more than 12 million people to this pathogen in Chile. This study has epidemiological and public health implications for the response to a potential C. bacillisporus outbreak, optimizing budgets, routing for screening diagnosis, and treatment implementation.

Disseminated cryptococcosis in an immunocompetent patient

Cryptococcosis is an important opportunistic infection. It is the third most common invasive fungal infection in solid organ transplant recipients. The primary organ affected is the lungs, but infection of the central nervous system and other organ systems are also seen. Here we reported a case of disseminated cryptococcosis in a healthy patient who presented with severe pneumonia, a left upper lobe nodule and enlarged mediastinal lymphadenopathy on a chest computed tomography scan.

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Cryptococcosis is an important opportunistic infection.

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A case of disseminated cryptococcosis in a healthy patient was reported.

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Chest CT revealed a left upper lobe nodule and enlarged mediastinal lymphadenopathy.

Cryptococcus neoformans and Cryptococcus gattii Species Complex Isolates on the Slopes of Mount Etna, SICILY, Italy

This study investigated the presence of Cryptococcus neoformans and Cryptococcus gattii species complex isolates on olive trees growing in the Eastern part of Sicily (Italy) characterized by the presence of the volcano Etna and the ability of these fungal pathogens to sexually reproduce on medium containing volcanic soil. Samples from 124 olive trees were collected from 14 different sites around Mount Etna. Eighteen trees (14.5%) resulted colonized by C. neoformans VNI-αA isolates, one (0.8%) by VNIV-αD isolates, and two (1.6%) by C. gattii VGI-αB isolates. The ability of environmental and reference strains belonging to VNI, VNIV, and VGI molecular types to sexually reproduce on a medium containing volcanic soil was also tested. VNI and VNIV strains were able to produce filaments and basiodiospores more vigorously than on the control medium, whereas VGI strains were not fertile. In conclusion, the present study identified which C. neoformans and C. gattii species complex genotypes are circulating in Eastern Sicily and confirmed the ecological role of olive trees as environmental reservoir of these pathogens. It also showed that Cryptococcus is able to colonize and sexually reproduce in inhospitable environments such as the slopes of a volcano.

Epidemiological, Clinical and Outcome Aspects of Patients with Cryptococcosis Caused by Cryptococcus gattii from a Non-endemic Area of Brazil

Cryptococcosis by Cryptococcus gattii occurs mainly in immunocompetent hosts, however, during the last decades, a growing number of cases in immunocompromised individuals have been noticed around the world. This report presents epidemiological, clinical and outcome aspects of patients with cryptococcosis caused by this species from a non-endemic area in Brazil. Of 278 Cryptococcus spp. clinical isolates recovered during the same period, 267 (96%) were molecularly identified as Cryptococcus neoformans VNI genotype and 11 (4%) as C. gattii VGII genotype by URA-5 RFLP. Of the 11 C. gattii patients, eight were male, mean age of 47.5 years. Of these, four were HIV-infected, one was kidney transplanted, one presented low CD4⁺ T cells values of unknown cause, another presented chronic liver disease meanwhile the remaining four were apparently immunocompetent. Disseminated disease and cryptococcal meningitis were present in four patients each. Most patients received amphotericin B plus fluconazole. Seven out of the 11 patients cured and four died before or during the therapy. The increased number of individuals with cryptococcosis by this species during the last decades needs to be carefully evaluated specially those who are HIV-infected. Nevertheless, Cryptococcus species differentiation is currently relevant in order to better know their relation with geographical, clinical host preference and outcome particularities.

Hybridization and emergence of virulence in opportunistic human yeast pathogens

Hybridization between different species can result in the emergence of new lineages and adaptive phenotypes. Occasionally, hybridization in fungal organisms can drive the appearance of opportunistic lifestyles or shifts to new hosts, resulting in the emergence of novel pathogens. In recent years, an increasing number of studies have documented the existence of hybrids in diverse yeast clades, including some comprising human pathogens. Comparative and population genomics studies performed on these clades are enabling us to understand what roles hybridization may play in the evolution and emergence of a virulence potential towards humans. Here we survey recent genomic studies on several yeast pathogenic clades where hybrids have been identified, and discuss the broader implications of hybridization in the evolution and emergence of pathogenic lineages. © 2017 The Authors. Yeast published by John Wiley & Sons, Ltd.

Transcriptional Analysis Allows Genome Reannotation and Reveals that Cryptococcus gattii VGII Undergoes Nutrient Restriction during Infection

Cryptococcus gattii is a human and animal pathogen that infects healthy hosts and caused the Pacific Northwest outbreak of cryptococcosis. The inhalation of infectious propagules can lead to internalization of cryptococcal cells by alveolar macrophages, a niche in which C. gattii cells can survive and proliferate. Although the nutrient composition of macrophages is relatively unknown, the high induction of amino acid transporter genes inside the phagosome indicates a preference for amino acid uptake instead of synthesis. However, the presence of countable errors in the R265 genome annotation indicates significant inhibition of transcriptomic analysis in this hypervirulent strain. Thus, we analyzed RNA-Seq data from in vivo and in vitro cultures of C. gattii R265 to perform the reannotation of the genome. In addition, based on in vivo transcriptomic data, we identified highly expressed genes and pathways of amino acid metabolism that would enable C. gattii to survive and proliferate in vivo. Importantly, we identified high expression in three APC amino acid transporters as well as the GABA permease. The use of amino acids as carbon and nitrogen sources, releasing ammonium and generating carbohydrate metabolism intermediaries, also explains the high expression of components of several degradative pathways, since glucose starvation is an important host defense mechanism.

Yeasts

Yeasts are unicellular organisms that reproduce mostly by budding and less often by fission. Most medically important yeasts originate from Ascomycota or Basidiomycota. Here, we review taxonomy, epidemiology, disease spectrum, antifungal drug susceptibility patterns of medically important yeast, laboratory diagnosis, and diagnostic strategies.

Predominance of Cryptococcus neoformans var. grubii multilocus sequence type 5 and emergence of isolates with non-wild-type minimum inhibitory concentrations to fluconazole: a multi-centre study in China

There are few data on the molecular epidemiology of cryptococcosis in China. Here we investigated the species distribution, molecular types and antifungal susceptibilities of 312 Cryptococcus neoformans species complex isolates from ten hospitals over 5 years. Isolates were identified by internal transcribed spacer (ITS) sequencing and by two matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems. Multilocus sequence typing (MLST) was used to verify species/variety and to designate molecular types. Susceptibility to six antifungal drugs was determined by the Sensititre YeastOne™ method. Cryptococcus neoformans was the predominant species (305/312 isolates (97.8%), all were ITS type 1, serotype A), of which 89.2% (272/305) were C. neoformans var. grubii MLST sequence type (ST) 5 and 6.2% (19/305) were ST31. Other C. neoformans var. grubii STs were rare but included six novel STs. Only two strains were C. neoformans var. neoformans (both serotype AD). Cryptococcus gattii was uncommon (n = 7, four ITS types) and comprised five MLST STs including one novel ST. For C. neoformans var. grubii, the proportion of isolates with non-wild-type MICs to fluconazole significantly rose in the fourth study year (from 0% (0/56 isolates) in the first year to 23.9% (17/71) in the fourth year), including five isolates with fluconazole MICs of ≥32 mg/L. The study has provided useful data on the species epidemiology and their genetic diversity and antifungal susceptibility. The proportional increase in isolates with non-wild-type MICs to fluconazole is noted.

Environmental distribution of Cryptococcus neoformans and C. gattii around the Mediterranean basin

In order to elucidate the distribution of Cryptococcus neoformans and C. gattii in the Mediterranean basin, an extensive environmental survey was carried out during 2012-2015. A total of 302 sites located in 12 countries were sampled, 6436 samples from 3765 trees were collected and 5% of trees were found to be colonized by cryptococcal yeasts. Cryptococcus neoformans was isolated from 177 trees and C. gattii from 13. Cryptococcus neoformans colonized 27% of Ceratonia, 10% of Olea, Platanus and Prunus trees and a lower percentage of other tree genera. The 13 C. gattii isolates were collected from five Eucalyptus, four Ceratonia, two Pinus and two Olea trees. Cryptococcus neoformans was distributed all around the Mediterranean basin, whereas C. gattii was isolated in Greece, Southern Italy and Spain, in agreement with previous findings from both clinical and environmental sources. Among C. neoformans isolates, VNI was the prevalent molecular type but VNII, VNIV and VNIII hybrid strains were also isolated. With the exception of a single VGIV isolate, all C. gattii isolates were VGI. The results confirmed the presence of both Cryptococcus species in the Mediterranean environment, and showed that both carob and olive trees represent an important niche for these yeasts.

A rare cause of cerebral venous thrombosis: cryptococcal meningoencephalitis

Cryptococcal meningoencephalitis (CM) is a serious central nervous system infection caused by Cryptococcus neoformans, seen mostly in immunocompromised hosts and less in immunocompetent patients. The vast majority of cryptococcosis cases are seen as human immunodeficiency virus infections with advanced immunosuppression. Meningitis and meningoencephalitis are the most common clinical manifestations. Nevertheless, immunocompetent patients with CM are rarely reported. Cerebral venous sinus thrombosis is a rare complication of CM. Here, we report an immunocompetent patient with CM from a non-endemic area, who presented with an acute onset and atypical symptoms associated with cerebral venous thrombosis.

What makes Cryptococcus gattii a pathogen?

Cryptococcosis is an invasive fungal infection of humans and other animals, typically caused by the species Cryptococcus neoformans in patients with impaired immunity. However, there is growing recognition of the importance of the related species C. gattii in causing infections in apparently immunocompetent individuals. In particular, an ongoing outbreak of cryptococcal disease in the Pacific Northwest region, which started in 1999, has driven an intense research effort into this previously neglected pathogen. Here, we discuss some of the recent discoveries in this organism from the Pacific Northwest region and highlight areas for future investigation.

Cryptococcus gattii infections

Understanding of the taxonomy and phylogeny of Cryptococcus gattii has been advanced by modern molecular techniques. C. gattii probably diverged from Cryptococcus neoformans between 16 million and 160 million years ago, depending on the dating methods applied, and maintains diversity by recombining in nature. South America is the likely source of the virulent C. gattii VGII molecular types that have emerged in North America. C. gattii shares major virulence determinants with C. neoformans, although genomic and transcriptomic studies revealed that despite similar genomes, the VGIIa and VGIIb subtypes employ very different transcriptional circuits and manifest differences in virulence phenotypes. Preliminary evidence suggests that C. gattii VGII causes severe lung disease and death without dissemination, whereas C. neoformans disseminates readily to the central nervous system (CNS) and causes death from meningoencephalitis. Overall, currently available data indicate that the C. gattii VGI, VGII, and VGIII molecular types more commonly affect nonimmunocompromised hosts, in contrast to VGIV. New, rapid, cheap diagnostic tests and imaging modalities are assisting early diagnosis and enabling better outcomes of cerebral cryptococcosis. Complications of CNS infection include increased intracranial pressure, severe neurological sequelae, and development of immune reconstitution syndrome, although the mortality rate is low. C. gattii VGII isolates may exhibit higher fluconazole MICs than other genotypes. Optimal therapeutic regimens are yet to be determined; in most cases, initial therapy with amphotericin B and 5-flucytosine is recommended.

Cryptococcus gattii VGIII isolates causing infections in HIV/AIDS patients in Southern California: identification of the local environmental source as arboreal

Ongoing Cryptococcus gattii outbreaks in the Western United States and Canada illustrate the impact of environmental reservoirs and both clonal and recombining propagation in driving emergence and expansion of microbial pathogens. C. gattii comprises four distinct molecular types: VGI, VGII, VGIII, and VGIV, with no evidence of nuclear genetic exchange, indicating these represent distinct species. C. gattii VGII isolates are causing the Pacific Northwest outbreak, whereas VGIII isolates frequently infect HIV/AIDS patients in Southern California. VGI, VGII, and VGIII have been isolated from patients and animals in the Western US, suggesting these molecular types occur in the environment. However, only two environmental isolates of C. gattii have ever been reported from California: CBS7750 (VGII) and WM161 (VGIII). The incongruence of frequent clinical presence and uncommon environmental isolation suggests an unknown C. gattii reservoir in California. Here we report frequent isolation of C. gattii VGIII MATα and MATa isolates and infrequent isolation of VGI MATα from environmental sources in Southern California. VGIII isolates were obtained from soil debris associated with tree species not previously reported as hosts from sites near residences of infected patients. These isolates are fertile under laboratory conditions, produce abundant spores, and are part of both locally and more distantly recombining populations. MLST and whole genome sequence analysis provide compelling evidence that these environmental isolates are the source of human infections. Isolates displayed wide-ranging virulence in macrophage and animal models. When clinical and environmental isolates with indistinguishable MLST profiles were compared, environmental isolates were less virulent. Taken together, our studies reveal an environmental source and risk of C. gattii to HIV/AIDS patients with implications for the >1,000,000 cryptococcal infections occurring annually for which the causative isolate is rarely assigned species status. Thus, the C. gattii global health burden could be more substantial than currently appreciated.

The environmentally-acquired human pathogen C. gattii is responsible for ongoing and expanding outbreaks in the Western United States and Canada. C. gattii comprises four distinct molecular types: VGI, VGII, VGIII, and VGIV. Molecular types VGI, VGII, and VGIII have been isolated from patients and animals throughout the Western US. The Pacific Northwest and Canadian outbreak is primarily caused by C. gattii VGII. VGIII is responsible for ongoing infections in HIV/AIDS patients in Southern California. However, only two environmental C. gattii isolates have ever been identified from the Californian environment: CBS7750 (VGII) and WM161 (VGIII). We sought to collect environmental samples from areas that had confirmed reports of clinical or veterinary infections. Here we report the isolation of C. gattii VGI and VGIII from environmental soil and tree samples. C. gattii isolates were obtained from three novel tree species: Canary Island pine, American sweetgum, and a Pohutukawa tree. Genetic analysis provides robust evidence that these environmental isolates are the source of human infections.

The cryptic sexual strategies of human fungal pathogens

Sexual reproduction is a pervasive attribute of eukaryotic species and is now recognized to occur in many clinically important human fungal pathogens. These fungi use sexual or parasexual strategies for various purposes that can have an impact on pathogenesis, such as the formation of drug-resistant isolates, the generation of strains with increased virulence or the modulation of interactions with host cells. In this Review, we examine the mechanisms regulating fungal sex and the consequences of these programmes for human disease.

Primary cutaneous cryptococcosis in an immunocompetent patient due to Cryptococcus gattii molecular type VGI in Brazil: a case report and review of literature

Primary Cutaneous Cryptococcosis is an uncommon infection caused by the yeast Cryptococcus neoformans and C. gattii. Few case reports are available in the literature describing in detail primary cutaneous cryptococcosis due to C. gattii in immunocompetent patients. Herein, we present a case of a 68-year-old immunocompetent male patient with erythematous nodular lesions on the right forearm due to C. gattii mating-type α and molecular type VGI. The virulence factors test was performed for capsule diameter, melanin production and phospholipase activity. In vitro fluconazole testing showed the sensitivity profile of this clinical isolate. In addition, a review of the literature on this subject was carried out and verified that this is the first reported case of VGI in the south-east region of Brazil.

Isavuconazole activity against Aspergillus lentulus, Neosartorya udagawae, and Cryptococcus gattii, emerging fungal pathogens with reduced azole susceptibility

Isavuconazole is an extended-spectrum triazole with in vitro activity against a wide variety of fungal pathogens. Clinical isolates of molds Aspergillus lentulus and Neosartorya udagawae and yeast Cryptococcus gattii VGII (implicated in the outbreak in the Pacific Northwest, North America) exhibit reduced susceptibilities to several azoles but higher susceptibilities to isavuconazole.

The production of monokaryotic hyphae by Cryptococcus neoformans can be induced by high temperature arrest of the cell cycle and is independent of same-sex mating

Cryptococcus neoformans is a heterothallic fungal pathogen of humans and animals. Although the fungus grows primarily as a yeast, hyphae are produced during the sexual phase and during a process called monokaryotic fruiting, which is also believed to involve sexual reproduction, but between cells of the same mating type. Here we report a novel monokaryotic fruiting mechanism that is dependent on the cell cycle and occurs in haploid cells in the absence of sexual reproduction. Cells grown at 37°C were found to rapidly produce hyphae (∼4 hrs) and at high frequency (∼40% of the population) after inoculation onto hyphae-inducing agar. Microscopic examination of the 37°C seed culture revealed a mixture of normal-sized and enlarged cells. Micromanipulation of single cells demonstrated that only enlarged cells were able to produce hyphae and genetic analysis confirmed that hyphae did not arise from α-α mating or endoduplication. Cell cycle analysis revealed that cells grown at 37°C had an increased population of cells in G2 arrest, with the proportion correlated with the frequency of monokaryotic fruiting. Cell sorting experiments demonstrated that enlarged cells were only found in the G2-arrested population and only this population contained cells able to produce hyphae. Treatment of cells at low temperature with the G2 cell cycle arrest agent, nocodazole, induced hyphal growth, confirming the role of the cell cycle in this process. Taken together, these results reveal a mating-independent mechanism for monokaryotic fruiting, which is dependent on the cell cycle for induction of hyphal competency.

Fungi typically grow vegetatively as either yeast or hyphae. Many of the major human fungal pathogens can generate both morphologies and are referred to as the dimorphic fungi. Cryptococcus neoformans is a yeast-like fungus that has not been traditionally thought to be dimorphic since hyphae production typically occurs during the mating process between cells of opposite mating types. However, C. neoformans also can generate the hyphal state from haploid cells (called monokaryotic or haploid fruiting) in the absence of the opposite mating type. Recent studies have shown that the mechanism behind this process also involves mating, however, the mating reaction occurs between cells of the same mating type. Here we describe a unique mechanism responsible for monokaryotic fruiting that is independent of mating and does not proceed through a diploid intermediate. Instead, the key requirement for hyphal induction appears to be cell cycle arrest. Importantly, arrested cells display an enlarged cell phenotype, which has been observed in vivo in recent reports and has been hypothesized to be a novel protection strategy against host defenses. C. neoformans appears to have an extensive morphological repertoire, which likely contributes to its success as both a pathogen and a saprophyte.

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 reports of clinical and environmental isolation of C. gattii in temperate climates strongly imply C. gattii occurs world-wide. 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 suggest 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 world-wide occurrence of the primary pathogen C. gattii.

Rare Cryptococus gattii infection in an immunocompetent dairy goat following a cesarean section

A 5-year-old dairy goat was presented seven weeks post cesarean section for incomplete healing of the incision site. Cytology revealed cryptococcal organisms that were confirmed by the Centers for Disease Control as Cryptococcus gattii type VGIIa. Most cryptococcomas were surgically removed, but some penetrated deep in to the muscular layers and likely into peritoneum. The goat was treated daily with oral fluconazole for 6 months, and had a normal life for almost 2 years.

Immunotherapy of Cryptococcus infections

Despite appropriate antifungal treatment, the management of cryptococcal disease remains challenging, especially in immunocompromised patients, such as human immunodeficiency virus-infected individuals and solid organ transplant recipients. During the past two decades, our knowledge of host immune responses against Cryptococcus spp. has been greatly advanced, and the role of immunomodulation in augmenting the response to infection has been investigated. In particular, the role of 'protective' Th1 (tumour necrosis factor-α, interferon (IFN)-γ, interleukin (IL)-12, and IL-18) and Th17 (IL-23 and IL-17) and 'non-protective' Th2 (IL-4, IL-10, and IL-13) cytokines has been extensively studied in vitro and in animal models of cryptococcal infection. Immunomodulation with monoclonal antibodies against the capsular polysaccharide glucuronoxylomannan, glucosylceramides, melanin and β-glucan and, lately, with radioimmunotherapy has also yielded promising results in animal models. As a balance between sufficiently protective Th1 responses and excessive inflammation is important for optimal outcome, the effect of immunotherapy may range from beneficial to deleterious, depending on factors related to the host, the infecting organism, and the immunomodulatory regimen. Clinical evidence supporting immunomodulation in patients with cryptococcal infection remains too limited to allow firm recommendations. Limited human data suggest a role for IFN-γ. Identification of surrogate markers characterizing patients' immunological status could possibly suggest candidate patients for immunotherapy and the type of immunomodulation to be administered.

Update on the epidemiology and management of cryptococcal meningitis

Despite recent improvements in the diagnosis and treatment of cryptococcosis, cryptococcal meningitis is responsible for > 600,000 deaths/year worldwide. The aim of this work is to provide an update on the developments in its epidemiology and management. Understanding the pathogenesis of Cryptococcus has improved, and new insights for the virulence of the fungus and the host response have enabled scientists to design new ways to confront this infection. Additionally, invertebrate model hosts have greatly facilitated the research in this field. Importantly, the epidemiology of Cryptococcus gattii has continued to evolve, and the emergence of this highly virulent species in immunocompetent populations, especially in Northwestern America and British Columbia, warrants increased awareness because delayed diagnosis and inappropriate antifungal therapy is associated with high mortality. Diagnosis remains a challenge, but new techniques for early and inexpensive identification of the pathogen are under development. Management can vary, based on the patient population (HIV-seropositive, organ transplant recipients or non-transplant/non-HIV). In most patients, amphotericin B with flucytosine continues to be the most appropriate induction therapy. However, in organ transplant recipients the use of liposomal amphotericin B improves mortality compared with deoxycholate amphotericin B. Also, the combination of amphotericin B with fluconazole seems to be a reasonable alternative, while fluconazole with flucytosine is superior to fluconazole monotherapy.

Clinical, epidemiological and outcome features of patients with cryptococcosis in Uberaba, Minas Gerais, Brazil

Nearly one million of cryptococcosis cases occur yearly around the world, involving mainly HIV-infected patients who are not receiving antiretroviral therapy (ART) or present poor adherence. This study aims to evaluate epidemiological, clinical and outcome aspects of patients with cryptococcosis from 1998-2010. Patients were prospectively recruited, and their medical and laboratory records were reviewed. A total of 131 cases were included, and of these, 119 (90.83%) had AIDS, 4 received a renal transplant, 2 presented systemic lupus erythematosus and 6 (4.6%) were apparently immunocompetent. Ninety-one (69.46%) were men, and the median age was 38.7 years. Cryptococcal meningitis (CM) was diagnosed in 103 (78.62%), whereas 28 (21.38%) had cryptococcal infection in other sites. Of patients with CM, 94 (91.26%) had AIDS being cryptococcosis the first defining illness in 61 (64.9%), while 37 (60.65%) of them presented simultaneously both diagnosis. Headache, altered mental status, papilledema and seizures at admission were significatively associated with a poor outcome. Of 163 different isolates, 155 (95.09%) were Cryptococcus neoformans and eight (4.88%) Cryptococcus gattii. Antifungal therapy was warranted in 8 (87.4%) patients with CM, but 46 (51.1%) died during the first days or weeks. Of 28 patients without CM, 21 (75%) received treatment, but 6 (28.6%) died. The poor outcome among this case series was similar to that reported from other developing countries, but it is paradoxal in Brazil where the ART is at free disposal in the public health services. Despite, at least 60-70% of patients present advanced immunosuppression when they receive the AIDS diagnosis.