Cryptococcus neoformans trehalose-6-phosphate synthase (tps1) promotes organ-specific virulence and fungal protection against multiple lines of host defenses.

Trehalose-6-phosphate synthase (TPS1) was identified as a virulence factor for Cryptococcus neoformans and a promising therapeutic target. This study reveals previously unknown roles of TPS1 in evasion of host defenses during pulmonary and disseminated phases of infection. In the pulmonary infection model, TPS1-deleted (tps1Δ) Cryptococci are rapidly cleared by mouse lungs whereas TPS1-sufficent WT (H99) and revertant (tps1Δ:TPS1) strains expand in the lungs and disseminate, causing 100% mortality. Rapid pulmonary clearance of tps1Δ mutant is T-cell independent and relies on its susceptibility to lung resident factors and innate immune factors, exemplified by tps1Δ but not H99 inhibition in a coculture with dispersed lung cells and its rapid clearance coinciding with innate leukocyte infiltration. In the disseminated model of infection, which bypasses initial lung-fungus interactions, tps1Δ strain remains highly attenuated. Specifically, tps1Δ mutant is unable to colonize the lungs from the bloodstream or expand in spleens but is capable of crossing into the brain, where it remains controlled even in the absence of T cells. In contrast, strains H99 and tps1Δ:TPS1 rapidly expand in all studied organs, leading to rapid death of the infected mice. Since the rapid pulmonary clearance of tps1Δ mutant resembles a response to acapsular strains, the effect of tps1 deletion on capsule formation in vitro and in vivo was examined. Tps1Δ cryptococci form capsules but with a substantially reduced size. In conclusion, TPS1 is an important virulence factor, allowing C. neoformans evasion of resident pulmonary and innate defense mechanisms, most likely via its role in cryptococcal capsule formation.

Cryptococcosis-a systematic review to inform the World Health Organization Fungal Priority Pathogens List.

Cryptococcosis causes a high burden of disease worldwide. This systematic review summarizes the literature on Cryptococcus neoformans and C. gattii infections to inform the World Health Organization's first Fungal Priority Pathogen List. PubMed and Web of Science were used to identify studies reporting on annual incidence, mortality, morbidity, antifungal resistance, preventability, and distribution/emergence in the past 10 years. Mortality rates due to C. neoformans were 41%-61%. Complications included acute renal impairment, raised intracranial pressure needing shunts, and blindness. There was moderate evidence of reduced susceptibility (MIC range 16-32 mg/l) of C. neoformans to fluconazole, itraconazole, ketoconazole, voriconazole, and amphotericin B. Cryptococcus gattii infections comprised 11%-33% of all cases of invasive cryptococcosis globally. The mortality rates were 10%-23% for central nervous system (CNS) and pulmonary infections, and ∼43% for bloodstream infections. Complications described included neurological sequelae (17%-27% in C. gattii infections) and immune reconstitution inflammatory syndrome. MICs were generally low for amphotericin B (MICs: 0.25-0.5 mg/l), 5-flucytosine (MIC range: 0.5-2 mg/l), itraconazole, posaconazole, and voriconazole (MIC range: 0.06-0.5 mg/l). There is a need for increased surveillance of disease phenotype and outcome, long-term disability, and drug susceptibility to inform robust estimates of disease burden.

Mucorales: A systematic review to inform the World Health Organization priority list of fungal pathogens.

The World Health Organization, in response to the growing burden of fungal disease, established a process to develop a fungal priority pathogens list (FPPL). This systematic review aimed to evaluate the epidemiology and impact of invasive fungal disease due to Mucorales. PubMed and Web of Science were searched to identify studies published between January 1, 2011 and February 23, 2021. Studies reporting on mortality, inpatient care, complications and sequelae, antifungal susceptibility, risk factors, preventability, annual incidence, global distribution, and emergence during the study time frames were selected. Overall, 24 studies were included. Mortality rates of up to 80% were reported. Antifungal susceptibility varied across agents and species, with the minimum inhibitory concentrations lowest for amphotericin B and posaconazole. Diabetes mellitus was a common risk factor, detected in 65%-85% of patients with mucormycosis, particularly in those with rhino-orbital disease (86.9%). Break-through infection was detected in 13.6%-100% on azole or echinocandin antifungal prophylaxis. The reported prevalence rates were variable, with some studies reporting stable rates in the USA of 0.094-0.117/10 000 discharges between 2011 and 2014, whereas others reported an increase in Iran from 16.8% to 24% between 2011 and 2015. Carefully designed global surveillance studies, linking laboratory and clinical data, are required to develop clinical breakpoints to guide antifungal therapy and determine accurate estimates of complications and sequelae, annual incidence, trends, and global distribution. These data will provide robust estimates of disease burden to refine interventions and better inform future FPPL.

Aspergillus fumigatus-a systematic review to inform the World Health Organization priority list of fungal pathogens.

Recognizing the growing global burden of fungal infections, the World Health Organization established a process to develop a priority list of fungal pathogens (FPPL). In this systematic review, we aimed to evaluate the epidemiology and impact of invasive infections caused by Aspergillus fumigatus to inform the first FPPL. The pre-specified criteria of mortality, inpatient care, complications and sequelae, antifungal susceptibility, risk factors, preventability, annual incidence, global distribution, and emergence were used to search for relevant articles between 1 January 2016 and 10 June 2021. Overall, 49 studies were eligible for inclusion. Azole antifungal susceptibility varied according to geographical regions. Voriconazole susceptibility rates of 22.2% were reported from the Netherlands, whereas in Brazil, Korea, India, China, and the UK, voriconazole susceptibility rates were 76%, 94.7%, 96.9%, 98.6%, and 99.7%, respectively. Cross-resistance was common with 85%, 92.8%, and 100% of voriconazole-resistant A. fumigatus isolates also resistant to itraconazole, posaconazole, and isavuconazole, respectively. The incidence of invasive aspergillosis (IA) in patients with acute leukemia was estimated at 5.84/100 patients. Six-week mortality rates in IA cases ranged from 31% to 36%. Azole resistance and hematological malignancy were poor prognostic factors. Twelve-week mortality rates were significantly higher in voriconazole-resistant than in voriconazole-susceptible IA cases (12/22 [54.5%] vs. 27/88 [30.7%]; P = .035), and hematology patients with IA had significantly higher mortality rates compared with solid-malignancy cases who had IA (65/217 [30%] vs. 14/78 [18%]; P = .04). Carefully designed surveillance studies linking laboratory and clinical data are required to better inform future FPPL.

Fusarium species,Scedosporium species, and Lomentospora prolificans: A systematic review to inform the World Health Organization priority list of fungal pathogens.

Recognizing the growing global burden of fungal infections, the World Health Organization established a process to develop a priority list of fungal pathogens (FPPL). In this systematic review, we aimed to evaluate the epidemiology and impact of infections caused by Fusarium spp., Scedosporium spp., and Lomentospora prolificans to inform the first FPPL. PubMed and Web of Sciences databases were searched to identify studies published between January 1, 2011 and February 23, 2021, reporting on mortality, complications and sequelae, antifungal susceptibility, preventability, annual incidence, and trends. Overall, 20, 11, and 9 articles were included for Fusarium spp., Scedosporium spp., and L. prolificans, respectively. Mortality rates were high in those with invasive fusariosis, scedosporiosis, and lomentosporiosis (42.9%-66.7%, 42.4%-46.9%, and 50.0%-71.4%, respectively). Antifungal susceptibility data, based on small isolate numbers, showed high minimum inhibitory concentrations (MIC)/minimum effective concentrations for most currently available antifungal agents. The median/mode MIC for itraconazole and isavuconazole were ≥16 mg/l for all three pathogens. Based on limited data, these fungi are emerging. Invasive fusariosis increased from 0.08 cases/100 000 admissions to 0.22 cases/100 000 admissions over the time periods of 2000-2009 and 2010-2015, respectively, and in lung transplant recipients, Scedosporium spp. and L. prolificans were only detected from 2014 onwards. Global surveillance to better delineate antifungal susceptibility, risk factors, sequelae, and outcomes is required.

Pichia kudriavzevii (Candida krusei): A systematic review to inform the World Health Organisation priority list of fungal pathogens.

In response to the growing global threat of fungal infections, in 2020 the World Health Organisation (WHO) established an Expert Group to identify priority fungi and develop the first WHO fungal priority pathogen list (FPPL). The aim of this systematic review was to evaluate the features and global impact of invasive infections caused by Pichia kudriavzevii (formerly known as Candida krusei). PubMed and Web of Science were used to identify studies published between 1 January 2011 and 18 February 2021 reporting on the criteria of mortality, morbidity (defined as hospitalisation and length of stay), drug resistance, preventability, yearly incidence, and distribution/emergence. Overall, 33 studies were evaluated. Mortality rates of up to 67% in adults were reported. Despite the intrinsic resistance of P. kudriavzevii to fluconazole with decreased susceptibility to amphotericin B, resistance (or non-wild-type rate) to other azoles and echinocandins was low, ranging between 0 and 5%. Risk factors for developing P. kudriavzevii infections included low birth weight, prior use of antibiotics/antifungals, and an underlying diagnosis of gastrointestinal disease or cancer. The incidence of infections caused by P. kudriavzevii is generally low (∼5% of all Candida-like blood isolates) and stable over the 10-year timeframe, although additional surveillance data are needed. Strategies targeting the identified risk factors for developing P. kudriavzevii infections should be developed and tested for effectiveness and feasibility of implementation. Studies presenting data on epidemiology and susceptibility of P. kudriavzevii were scarce, especially in low- and middle-income countries (LMICs). Thus, global surveillance systems are required to monitor the incidence, susceptibility, and morbidity of P. kudriavzevii invasive infections to inform diagnosis and treatment. Timely species-level identification and susceptibility testing should be conducted to reduce the high mortality and limit the spread of P. kudriavzevii in healthcare facilities.

The Rabbit Model of Cryptococcal Meningitis.

Cryptococcal meningitis (CM) is a fungal disease caused by the invasion of Cryptococcus yeast cells into the central nervous system. The organism is thought to enter the body through the lungs and then escape due to dysregulation of the immune response. Multiple animal species have been used to model the infection and characterize CM including mice, rats, dogs, guinea pigs, and rabbits. The rabbit model has over 40 years of data and has been used to study host-pathogen interactions and the efficacy of antifungal therapeutics. The model begins with immune suppression to eliminate the lymphocytic cell population followed by direct infection of the central nervous system via an injection of a suspension of yeast cells into the cisterna magna. The organism remains in the CNS during the course of infection, and cerebrospinal fluid can be repeatedly sampled to quantify the burden of organism, measure drug levels in the CSF, profile the immune response in the CSF, and/or characterize the yeast cells. The rabbit model of infection is a robust experimental model for better understanding CM and Cryptococcus cellular behavior.

Biolistic Transformation of Cryptococcus neoformans.

Biolistic transformation of Cryptococcus neoformans is used as a molecular tool to genetically alter or delete targeted genes. The DNA is introduced into the yeast on DNA-coated gold beads by a helium shock wave produced using a biolistic particle system. The procedure often involves insertion of a dominant selectable marker into the desired site by homologous recombination. To increase the likelihood of homologous recombination, large fragments of overlapping DNA are used. The two most used dominant selectable markers are nourseothricin and Geneticin. With the need to generate multiple gene deletions in the same strain, there are recyclable marker systems, such as the bacteriophage P1 Cre-loxP system or CRISPR that provide additional useful molecular tools. While newer strategies exist to generate deletions and introduce markers and other gene modifications, biolistic transformation has remained a viable tool to facilitate the construction of genetically modified yeast strains. This chapter provides a working protocol on how to delete and restore a gene in C. neoformans.

A ketogenic diet enhances fluconazole efficacy in murine models of systemic fungal infection.

Invasive fungal infections are a significant public health concern, with mortality rates ranging from 20% to 85% despite current treatments. Therefore, we examined whether a ketogenic diet could serve as a successful treatment intervention in murine models of Cryptococcus neoformans and Candida albicans infection in combination with fluconazole-a low-cost, readily available antifungal therapy. The ketogenic diet is a high-fat, low-carbohydrate diet that promotes fatty acid oxidation as an alternative to glycolysis through the production of ketone bodies. In this series of experiments, mice fed a ketogenic diet prior to infection with C. neoformans and treated with fluconazole had a significant decrease in fungal burden in both the brain (mean 2.66 ± 0.289 log10 reduction) and lung (mean 1.72 ± 0.399 log10 reduction) compared to fluconazole treatment on a conventional diet. During C. albicans infection, kidney fungal burden of mice in the keto-fluconazole combination group was significantly decreased compared to fluconazole alone (2.37 ± 0.770 log10-reduction). Along with higher concentrations of fluconazole in the plasma and brain tissue, fluconazole efficacy was maximized at a significantly lower concentration on a keto diet compared to a conventional diet, indicating a dramatic effect on fluconazole pharmacodynamics. Our findings indicate that a ketogenic diet potentiates the effect of fluconazole at multiple body sites during both C. neoformans and C. albicans infection and could have practical and promising treatment implications.IMPORTANCEInvasive fungal infections cause over 2.5 million deaths per year around the world. Treatments for fungal infections are limited, and there is a significant need to develop strategies to enhance antifungal efficacy, combat antifungal resistance, and mitigate treatment side effects. We determined that a high-fat, low-carbohydrate ketogenic diet significantly potentiated the therapeutic effect of fluconazole, which resulted in a substantial decrease in tissue fungal burden of both C. neoformans and C. albicans in experimental animal models. We believe this work is the first of its kind to demonstrate that diet can dramatically influence the treatment of fungal infections. These results highlight a novel strategy of antifungal drug enhancement and emphasize the need for future investigation into dietary effects on antifungal drug activity.

Hormonal steroids induce multidrug resistance and stress response genes in Neisseria gonorrhoeae by binding to MtrR.

Transcriptional regulator MtrR inhibits the expression of the multidrug efflux pump operon mtrCDE in the pathogenic bacterium Neisseria gonorrhoeae. Here, we show that MtrR binds the hormonal steroids progesterone, ß-estradiol, and testosterone, which are present at urogenital infection sites, as well as ethinyl estrogen, a component of some hormonal contraceptives. Steroid binding leads to the decreased affinity of MtrR for cognate DNA, increased mtrCDE expression, and enhanced antimicrobial resistance. Furthermore, we solve crystal structures of MtrR bound to each steroid, thus revealing their binding mechanisms and the conformational changes that induce MtrR.

Risk factors, management, and clinical outcomes of invasive Mycoplasma and Ureaplasma infections after lung transplantation.

Mollicute infections, caused by Mycoplasma and Ureaplasma species, are serious complications after lung transplantation; however, understanding of the epidemiology and outcomes of these infections remains limited. We conducted a single-center retrospective study of 1156 consecutive lung transplants performed from 2010-2019. We used log-binomial regression to identify risk factors for infection and analyzed clinical management and outcomes. In total, 27 (2.3%) recipients developed mollicute infection. Donor characteristics independently associated with recipient infection were age ≤40 years (prevalence rate ratio [PRR] 2.6, 95% CI 1.0-6.9), White race (PRR 3.1, 95% CI 1.1-8.8), and purulent secretions on donor bronchoscopy (PRR 2.3, 95% CI 1.1-5.0). Median time to diagnosis was 16 days posttransplant (IQR: 11-26 days). Mollicute-infected recipients were significantly more likely to require prolonged ventilatory support (66.7% vs 21.4%), undergo dialysis (44.4% vs 6.3%), and remain hospitalized ≥30 days (70.4% vs 27.4%) after transplant. One-year posttransplant mortality in mollicute-infected recipients was 12/27 (44%), compared to 148/1129 (13%) in those without infection (P <.0001). Hyperammonemia syndrome occurred in 5/27 (19%) mollicute-infected recipients, of whom 3 (60%) died within 10 weeks posttransplant. This study highlights the morbidity and mortality associated with mollicute infection after lung transplantation and the need for better screening and management protocols.

Description of Cryptococcosis Following SARS-CoV-2 Infection: A Disease Survey Through the Mycosis Study Group Education and Research Consortium (MSG-19).

BACKGROUND: Invasive fungal infections have been described throughout the COVID-19 pandemic. Cryptococcal disease after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been reported in several isolated case reports and 1 larger case series. We sought to describe cryptococcal infections following SARS-CoV-2 through establishing a database to investigate underlying risk factors, disease manifestations, and outcomes. METHODS: We created a crowdsourced call for cases solicited through the Mycoses Study Group Education and Research Consortium, the Centers for Disease Control and Prevention Emerging Infectious Diseases Network, and infectious diseases Twitter groups. Data were collected in a web-based and secure REDCap survey without personal identifiers. RESULTS: Sixty-nine cases were identified and submitted by 29 separate institutional sites. Cryptococcosis was diagnosed a median of 22 days (interquartile range, 9-42 days) after SARS-CoV-2 infection. Mortality among those with available follow-up was 72% (26/36) for the immunocompetent group and 48% (15/31) for the immunocompromised group (likelihood ratio, 4.01; P = .045). We observed a correlation between disease manifestation (central nervous system infection, proven/probable disseminated disease, and respiratory) and mortality (P = .002). CONCLUSIONS: The mortality rate of 59% for patients with cryptococcosis following SARS-CoV-2 is higher than that of modern Cryptococcus cohorts. There was an association between immunocompromised status and cryptococcal disease manifestations as well as mortality. Moreover, our series emphasizes the need for clinical and laboratory assessment of opportunistic infections beyond 30 days when concerning symptoms develop.

Genetic diversity and microevolution in clinical Cryptococcus isolates from Cameroon.

Cryptococcal meningitis is the second most common cause of death in people living with HIV/AIDS, yet we have a limited understanding of how cryptococcal isolates change over the course of infection. Cryptococcal infections are environmentally acquired, and the genetic diversity of these infecting isolates can also be geographically linked. Here, we employ whole genome sequences for 372 clinical Cryptococcus isolates from 341 patients with HIV-associated cryptococcal meningitis obtained via a large clinical trial, across both Malawi and Cameroon, to enable population genetic comparisons of isolates between countries. We see that isolates from Cameroon are highly clonal, when compared to those from Malawi, with differential rates of disruptive variants in genes with roles in DNA binding and energy use. For a subset of patients (22) from Cameroon, we leverage longitudinal sampling, with samples taken at days 7 and 14 post-enrollment, to interrogate the genetic changes that arise over the course of infection, and the genetic diversity of isolates within patients. We see disruptive variants arising over the course of infection in several genes, including the phagocytosis-regulating transcription factor GAT204. In addition, in 13% of patients sampled longitudinally, we see evidence for mixed infections. This approach identifies geographically linked genetic variation, signatures of microevolution, and evidence for mixed infections across a clinical cohort of patients affected by cryptococcal meningitis in Central Africa.

Cryptococcal meningitis, caused by Cryptococcus, results in approximately half a million deaths per year globally. We compare clinical Cryptococcus samples from Cameroon and Malawi to explore the genetic diversity of these isolates. We find instances of mixed-strain infections and identify genetic variants arising in Cryptococcus over disease.

Development and validation of a colorimetric antifungal susceptibility testing method for the dimorphic fungus Talaromyces marneffei.

Antifungal drug resistance is an emerging cause of treatment failure in invasive fungal infections, and antifungal susceptibility testing (AFST) may inform treatment decisions. Currently, there are no established AFST guidelines for Talaromyces marneffei (Tm) or other dimorphic fungi. We developed a colorimetric AFST method using a fluorescent redox indicator alamarBlue, which changes from blue to pink in proportion to cellular metabolic activity. We determined the optimal time for alamarBlue addition to be 24 h post-inoculation and for MIC reading to be 72 h post-inoculation. Our method allows three ways to determine minimum inhibitory concentration (MIC): visual inspection of color change, optical density, and fluorescence intensity. We validated the assay by determining the MICs for seven antifungals against 32 Tm clinical isolates and assessed the essential agreement (EA) and inter-rater reliability between our alamarBlue and the Clinical Laboratory Standard Institute (CLSI) broth microdilution methods. The MIC ranges (from low to high) were: 0.008-0.025 µg/ml for itraconazole, 0.004-0.13 µg/ml for voriconazole, 0.03-0.13 µg/ml for posaconazole, 0.06-0.5 µg/ml for flucytosine, 0.5-1 µg/ml for amphotericin B, 0.5-4 µg/ml for caspofungin, and 0.5-16 µg/ml for fluconazole. The EAs were 100% between all three MIC readouts of the alamarBlue method, and 94%-100% between the alamarBlue and CLSI methods. Our alamarBlue method had substantially higher inter-rater agreement and offers a more reliable method that can be standardized across laboratories in both high- and low-resource settings compared to the established CLSI methodology.

We developed a colorimetric alamarBlue method to determine the susceptibility of antifungal drugs against Talaromyces marneffei. We observed excellent agreement between the alamarBlue method and the Clinical Laboratory Standard Institute broth microdilution method, and the alamarBlue method had substantially higher inter-rater agreement.

HIV and fungal priority pathogens.

The burden of invasive fungal infections associated with opportunistic fungal pathogens is a persistent challenge, particularly among people with advanced HIV disease. In October, 2022, WHO published the Fungal Priority Pathogens List (FPPL)-the first global effort to systematically prioritise fungal pathogens. Of the 19 pathogens in the WHO FPPL, four opportunistic pathogens in particular cause invasive diseases in people living with HIV: Cryptococcus neoformans, Histoplasma spp, Pneumocystis jirovecii, and Talaromyces marneffei. These four fungal pathogens are major causes of illness and death in people with advanced HIV and overwhelmingly affect those in low-income and middle-income countries. Access to diagnostics, improved surveillance, targeted support for innovation, and an enhanced public health focus on these diseases are needed in the effort to reduce HIV-associated deaths.

Pharmacodynamics of ATI-2307 in a rabbit model of cryptococcal meningoencephalitis.

Cryptococcal meningoencephalitis (CM) is a devastating fungal disease with high morbidity and mortality. The current regimen that is standard-of-care involves a combination of three different drugs administered for up to one year. There is a critical need for new therapies due to both toxicity and inadequate fungicidal activity of the currently available antifungal drugs. ATI-2307 is a novel aryl amidine that disrupts the mitochondrial membrane potential and inhibits the respiratory chain complexes of fungi-it thus represents a new mechanism for direct antifungal action. Furthermore, ATI-2307 selectively targets fungal mitochondria via a fungal-specific transporter that is not present in mammalian cells. It has very potent in vitro anticryptococcal activity. In this study, the efficacy of ATI-2307 was tested in a rabbit model of CM. ATI-2307 demonstrated significant fungicidal activity at dosages between 1 and 2 mg/kg/d, and these results were superior to fluconazole and similar to amphotericin B treatment. When ATI-2307 was combined with fluconazole, the antifungal effect was greater than either therapy alone. While ATI-2307 has potent anticryptococcal activity in the subarachnoid space, its ability to reduce yeasts in the brain parenchyma was relatively less over the same study period. This new drug, with its unique mechanism of fungicidal action and ability to positively interact with an azole, has demonstrated sufficient anticryptococcal potential in this experimental setting to be further evaluated in clinical studies.

Hormonal steroids bind the Neisseria gonorrhoeae multidrug resistance regulator, MtrR, to induce a multidrug binding efflux pump and stress-response sigma factor.

Overexpression of the multidrug efflux pump MtrCDE, a critical factor of multidrug-resistance in Neisseria gonorrhoeae , the causative agent of gonorrheae, is repressed by the transcriptional regulator, MtrR (multiple transferable resistance repressor). Here, we report the results from a series of in vitro experiments to identify innate, human inducers of MtrR and to understand the biochemical and structural mechanisms of the gene regulatory function of MtrR. Isothermal titration calorimetry experiments reveal that MtrR binds the hormonal steroids progesterone, ß-estradiol, and testosterone, all of which are present at significant concentrations at urogenital infection sites as well as ethinyl estrogen, a component of some birth control pills. Binding of these steroids results in decreased affinity of MtrR for cognate DNA, as demonstrated by fluorescence polarization-based assays. The crystal structures of MtrR bound to each steroid provided insight into the flexibility of the binding pocket, elucidated specific residue-ligand interactions, and revealed the conformational consequences of the induction mechanism of MtrR. Three residues, D171, W136 and R176 are key to the specific binding of these gonadal steroids. These studies provide a molecular understanding of the transcriptional regulation by MtrR that promotes N. gonorrhoeae survival in its human host.