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

Molecular characterization of clinical and environmental isolates from the Cryptococcus neoformans/C. Gattii species complexes of Maceió, Alagoas, Brazil

Cryptococcosis is one of the major life-threatening opportunistic/systemic fungal diseases of worldwide occurrence, which can be asymptomatic or establish pneumonia and meningoencephalitis mainly in immunosuppressed patients, caused by the Cryptococcus neoformans and C. gattii species complexes. Acquisition is by inhaling fungal propagules from avian droppings, tree hollows and decaying wood, and the association of the molecular types with geographic origin, virulence and antifungal resistance have epidemiological importance. Since data on cryptococcosis in Alagoas are limited, we sought to determine the molecular types of etiological agents collected from clinical and environmental sources. We evaluated 21 isolates previously collected from cerebrospinal fluid and from environment sources (pigeon droppings and tree hollows) in Maceió-Alagoas (Brazil). Restriction fragment length polymorphism of URA5 gene was performed to characterize among the eight standard molecular types (VNI-VNIV and VGI-VGIV). Among isolates, 66.67% (14) were assigned to C. neoformans VNI - 12 of them (12/14) recovered from liquor and 2 from a tree hollow (2/14). One isolate from pigeon droppings (4.76%) corresponded to C. neoformans VNIV, while five strains from tree hollows and one from pigeon droppings (6, 28.57%) to C. gattii VGII. VNI-type was present in clinical and environmental samples and most C. neoformans infections were observed in HIV-positive patients, while types VNIV and VGII were prevalent in environmental sources in Alagoas. This is the first molecular characterization of Cryptococcus spp. in Alagoas, our study provides additional information on the ecoepidemiology of Cryptococcus spp. in Brazil, contributing to a closer view of the endemic species.

Design of a cryptococcus neoformans vaccine by subtractive proteomics combined with immunoinformatics

The emergence of Cryptococcus neoformans has posed an undeniable burden to many regions worldwide, with its strains mainly entering the lungs through the respiratory tract and spreading throughout the body. Limitations of drug regimens, such as high costs and limited options, have directed our attention toward the promising field of vaccine development. In this study, the subtractive proteomics approach was employed to select target proteins from databases that can accurately cover serotypes A and D of the Cryptococcus neoformans. Further, two multi-epitope vaccines consisting of T and B cell epitopes were demonstrated that they have good structural stability and could bind with immune receptor to induce desired immune responses in silico. After further evaluation, these vaccines show the potential for large-scale production and applicability to the majority of the population of the world. In summary, these two vaccines have been theoretically proven to combat Cryptococcus neoformans infections, awaiting further experimental validation of their actual protective effects.

Cryptococcus: History, Epidemiology and Immune Evasion

Cryptococcosis is a disease caused by the pathogenic fungi Cryptococcus neoformans and Cryptococcus gattii, both environmental fungi that cause severe pneumonia and may even lead to cryptococcal meningoencephalitis. Although C. neoformans affects more fragile individuals, such as immunocompromised hosts through opportunistic infections, C. gattii causes a serious indiscriminate primary infection in immunocompetent individuals. Typically seen in tropical and subtropical environments, C. gattii has increased its endemic area over recent years, largely due to climatic factors that favor contagion in warmer climates. It is important to point out that not only C. gattii, but the Cryptococcus species complex produces a polysaccharidic capsule with immunomodulatory properties, enabling the pathogenic species of Cryptococccus to subvert the host immune response during the establishment of cryptococcosis, facilitating its dissemination in the infected organism. C. gattii causes a more severe and difficult-to-treat infection, with few antifungals eliciting an effective response during chronic treatment. Much of the immunopathology of this cryptococcosis is still poorly understood, with most studies focusing on cryptococcosis caused by the species C. neoformans. C. gattii became more important in the epidemiological scenario with the outbreaks in the Pacific Northwest of the United States, which resulted in phylogenetic studies of the virulent variant responsible for the severe infection in the region. Since then, the study of cryptococcosis caused by C. gattii has helped researchers understand the immunopathological aspects of different variants of this pathogen.

The Sweet Side of Fungal Infections: Structural Glycan Diversity and Its Importance for Pathogenic Adaptation

Fungal infections are the most common secondary infections in debilitated individuals in a state of chronic disease or immunosuppression. Despite this, most fungal infections are neglected, mainly due to the lower frequency of their more severe clinical forms in immunocompetent individuals with a healthy background. However, over the past few years, several cases of severe fungal infections in healthy individuals have provoked a change in the epidemiological dynamics of fungal infections around the world, both due to recurrent outbreaks in previously infrequent regions and the greater emergence of more pathogenic fungal variants affecting healthy individuals, such as in the Cryptococcus genus. Therefore, before the arrival of a scenario of prevalent severe fungal infections, it is necessary to assess more carefully what are the real reasons for the increased incidence of fungal infection globally. What are the factors that are currently contributing to this new possible epidemiological dynamic? Could these be of a structural nature? Herein, we propose a discussion based on the importance of the virulence factors of glycoconjugate composition in the adaptation of pathogenic fungal species into the current scenario of increasing severity of these infections.

Early clinical and microbiological predictors of outcome in hospitalized patients with cryptococcal meningitis

Background

Cryptococcal meningitis causes high mortality in immunocompromised and immunocompetent patients. The objective of this study was to identify early predictors of clinical outcome, available at the first days of hospitalization, in patients with cryptococcal meningitis in a tertiary center in Brazil.

Methods

Ninety-six cases of cryptococcal meningitis with clinical, epidemiological and laboratory data, and identification and antifungal susceptibility of the strains were analyzed. Quantitative CSF yeast counts were performed by direct microscopic exam with a Fuchs-Rosenthal cell counting chamber using an institutional protocol. Univariable and multiple analyses using logistic regression were performed to identify predictors, available at the beginning of hospitalization, of in-hospital mortality. Moreover, we performed a secondary analysis for a composite outcome defined by hospital mortality and intensive care unit transfer.

Results

The species and the antifungal susceptibility were not associated with the outcomes evaluated. The variables significantly associated with the mortality were age (OR = 1.08, 95% CI 1.02–1.15), the cerebrospinal fluid (CSF) yeasts count (OR = 1.65, 95% CI 1.20–2.27), systemic arterial hypertension (OR = 22.63, 95% CI 1.64–312.91) and neurological impairment identified by computed tomography (OR = 41.73, 95% CI 3.10–561.65). At the secondary analysis, CSF yeast count was also associated with the composite outcome, in addition to the culture of Cryptococcus spp. from bloodstream and cerebral toxoplasmosis. The associations were consistent with survival models evaluated.

Conclusions

Age and CSF yeast count were independently associated with in-hospital mortality of patients with cryptococcal meningitis but Cryptococcus species identification and antifungal susceptibility were not associated with the outcomes. Quantitative CSF yeast counts used in this study can be evaluated and implemented in other low and middle-income settings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07118-7.

Phenotypic Plasticity in the Productions of Virulence Factors Within and Among Serotypes in the Cryptococcus neoformans Species Complex

The Cryptococcus neoformans species complex (CNSC) is a common opportunistic human fungal pathogen and the most frequent cause of fungal meningitis. There are three major serotypes in CNSC: A, D, and their hybrids AD, and they have different geographic distributions and medical significance. Melanin pigment and a polysaccharide capsule are the two major virulence factors in CNSC. However, the relationships between serotype and virulence factor production and how environmental factors might impact their relationships are not known. This study investigated the expressions of melanin and capsular polysaccharide in a genetically diverse group of CNSC strains and how their phenotypic expressions were influenced by oxidative and nitrosative stress levels. We found significant differences in melanin and capsular polysaccharide productions among serotypes and across stress conditions. Under oxidative stress, the laboratory hybrids exhibited the highest phenotypic plasticity for melanin production while serotype A showed the highest for capsular polysaccharide production. In contrast, serotype D exhibited the highest phenotypic plasticity for capsular polysaccharide production and clinical serotype AD the highest phenotypic plasticity for melanin production under nitrosative stress. These results demonstrated that different serotypes have different environmental condition-specific mechanisms to modulate the expression of virulence factors.

Cryptococcosis by Cryptococcus neoformans/Cryptococcus gattii Species Complexes in non-HIV-Infected Patients in Southeastern Brazil

INTRODUCTION:

The clinical manifestations of cryptococcosis are usually associated with the infecting agents Cryptococcus neoformans (CN) and C. gattii (CG) species complexes and the host. In this study, non-HIV-infected patients, at a university hospital in southeastern Brazil, had epidemiological and clinical data associated with cryptococcal disease and isolated Cryptococcus species: CN - 24 patients and CG - 12 patients.

METHODS:

The comparison was comprised of demographic data, predisposing factors, clinical and laboratory manifestations, and outcomes of cryptococcosis patients treated between 2000 and 2016. Immunocompetent and immunosuppressed patients were also compared, irrespective of the infecting species. Cryptococcus spp. were genotyped by PCR-RFLP analysis of the URA5 gene.

RESULTS:

Infections by the CN species complex (100% VNI genotype) were associated with drug immunosuppression and fungemia, and patients infected with the CG species complex (83% VG II and 17% VGI genotypes) had more evident environmental exposure and higher humoral response. CN and CG affected patients with or without comorbidities.

CONCLUSIONS:

Diabetes mellitus, other chronic non-infectious diseases, and alcoholism were likely predisposing factors for infection by both CN and CG species. Immunocompetent patients, independent of the infecting Cryptococcus species complexes, showed a higher occurrence of meningitis and a trend toward less fungal dissemination and longer survival than immunosuppressed hosts.

Update on Pulmonary Cryptococcosis

Pulmonary cryptococcosis is a common but underdiagnosed opportunistic fungal infection in both immunocompromised and immunocompetent patients. The causal agents include at least eight evolutionary distinct haploid lineages as well as their hybrids of the human pathogenic Cryptococcus complex. In this update, we review recent advances in epidemiology, mode of transmission, risk factors, diagnostic methods, and therapy of pulmonary cryptococcosis. Our review suggests significant challenges and opportunities for research, from bedside to benchside and back to bedside.

Cryptococcus neoformans and Cryptococcus gattii Species Complexes in Latin America: A Map of Molecular Types, Genotypic Diversity, and Antifungal Susceptibility as Reported by the Latin American Cryptococcal Study Group

Cryptococcosis, a potentially fatal mycosis, is caused by members of the Cryptococcus neoformans and Cryptococcus gattii species complexes. In Latin America, cryptococcal meningitis is still an important health threat with a significant clinical burden. Analysis of publicly available molecular data from 5686 clinical, environmental, and veterinary cryptococcal isolates from member countries of the Latin American Cryptococcal Study Group showed that, as worldwide, C. neoformans molecular type VNI is the most common cause of cryptococcosis (76.01%) in HIV-infected people, followed by C. gattii molecular type VGII (12.37%), affecting mostly otherwise healthy hosts. These two molecular types also predominate in the environment (68.60% for VNI and 20.70% for VGII). Among the scarce number of veterinary cases, VGII is the predominant molecular type (73.68%). Multilocus sequence typing analysis showed that, in Latin America, the C. neoformans population is less diverse than the C. gattii population (D of 0.7104 vs. 0.9755). Analysis of antifungal susceptibility data showed the presence of non-wild-type VNI, VGI, VGII, and VGIII isolates in the region. Overall, the data presented herein summarize the progress that has been made towards the molecular epidemiology of cryptococcal isolates in Latin America, contributing to the characterization of the genetic diversity and antifungal susceptibility of these globally spreading pathogenic yeasts.