Browsing by Author "Dromer, Françoise"

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Open Access
Cryptococcal cell morphology affects host cell interactions and pathogenicity.
(PLoS Pathog, 2010-06-17) Okagaki, Laura H; Strain, Anna K; Nielsen, Judith N; Charlier, Caroline; Baltes, Nicholas J; Chrétien, Fabrice; Heitman, Joseph; Dromer, Françoise; Nielsen, Kirsten
Cryptococcus neoformans is a common life-threatening human fungal pathogen. The size of cryptococcal cells is typically 5 to 10 microm. Cell enlargement was observed in vivo, producing cells up to 100 microm. These morphological changes in cell size affected pathogenicity via reducing phagocytosis by host mononuclear cells, increasing resistance to oxidative and nitrosative stress, and correlated with reduced penetration of the central nervous system. Cell enlargement was stimulated by coinfection with strains of opposite mating type, and ste3aDelta pheromone receptor mutant strains had reduced cell enlargement. Finally, analysis of DNA content in this novel cell type revealed that these enlarged cells were polyploid, uninucleate, and produced daughter cells in vivo. These results describe a novel mechanism by which C. neoformans evades host phagocytosis to allow survival of a subset of the population at early stages of infection. Thus, morphological changes play unique and specialized roles during infection.
Open Access
Leave no one behind: response to new evidence and guidelines for the management of cryptococcal meningitis in low-income and middle-income countries.
(The Lancet. Infectious Diseases, 2019-04) Loyse, Angela; Burry, Jessica; Cohn, Jennifer; Ford, Nathan; Chiller, Tom; Ribeiro, Isabela; Koulla-Shiro, Sinata; Mghamba, Janneth; Ramadhani, Angela; Nyirenda, Rose; Aliyu, Sani H; Wilson, Douglas; Le, Thuy; Oladele, Rita; Lesikari, Sokoine; Muzoora, Conrad; Kalata, Newton; Temfack, Elvis; Mapoure, Yacouba; Sini, Victor; Chanda, Duncan; Shimwela, Meshack; Lakhi, Shabir; Ngoma, Jonathon; Gondwe-Chunda, Lilian; Perfect, Chase; Shroufi, Amir; Andrieux-Meyer, Isabelle; Chan, Adrienne; Schutz, Charlotte; Hosseinipour, Mina; Van der Horst, Charles; Klausner, Jeffrey D; Boulware, David R; Heyderman, Robert; Lalloo, David; Day, Jeremy; Jarvis, Joseph N; Rodrigues, Marcio; Jaffar, Shabbar; Denning, David; Migone, Chantal; Doherty, Megan; Lortholary, Olivier; Dromer, Françoise; Stack, Muirgen; Molloy, Síle F; Bicanic, Tihana; van Oosterhout, Joep; Mwaba, Peter; Kanyama, Cecilia; Kouanfack, Charles; Mfinanga, Sayoki; Govender, Nelesh; Harrison, Thomas S
In 2018, WHO issued guidelines for the diagnosis, prevention, and management of HIV-related cryptococcal disease. Two strategies are recommended to reduce the high mortality associated with HIV-related cryptococcal meningitis in low-income and middle-income countries (LMICs): optimised combination therapies for confirmed meningitis cases and cryptococcal antigen screening programmes for ambulatory people living with HIV who access care. WHO's preferred therapy for the treatment of HIV-related cryptococcal meningitis in LMICs is 1 week of amphotericin B plus flucytosine, and the alternative therapy is 2 weeks of fluconazole plus flucytosine. In the ACTA trial, 1-week (short course) amphotericin B plus flucytosine resulted in a 10-week mortality of 24% (95% CI -16 to 32) and 2 weeks of fluconazole and flucytosine resulted in a 10-week mortality of 35% (95% CI -29 to 41). However, with widely used fluconazole monotherapy, mortality because of HIV-related cryptococcal meningitis is approximately 70% in many African LMIC settings. Therefore, the potential to transform the management of HIV-related cryptococcal meningitis in resource-limited settings is substantial. Sustainable access to essential medicines, including flucytosine and amphotericin B, in LMICs is paramount and the focus of this Personal View.
Open Access
Microevolution of Serial Clinical Isolates of Cryptococcus neoformans var. grubii and C. gattii.
(MBio, 2017-03-07) Chen, Yuan; Farrer, Rhys A; Giamberardino, Charles; Sakthikumar, Sharadha; Jones, Alexander; Yang, Timothy; Tenor, Jennifer L; Wagih, Omar; Van Wyk, Marelize; Govender, Nelesh P; Mitchell, Thomas G; Litvintseva, Anastasia P; Cuomo, Christina A; Perfect, John R
The pathogenic species of Cryptococcus are a major cause of mortality owing to severe infections in immunocompromised as well as immunocompetent individuals. Although antifungal treatment is usually effective, many patients relapse after treatment, and in such cases, comparative analyses of the genomes of incident and relapse isolates may reveal evidence of determinative, microevolutionary changes within the host. Here, we analyzed serial isolates cultured from cerebrospinal fluid specimens of 18 South African patients with recurrent cryptococcal meningitis. The time between collection of the incident isolates and collection of the relapse isolates ranged from 124 days to 290 days, and the analyses revealed that, during this period within the patients, the isolates underwent several genetic and phenotypic changes. Considering the vast genetic diversity of cryptococcal isolates in sub-Saharan Africa, it was not surprising to find that the relapse isolates had acquired different genetic and correlative phenotypic changes. They exhibited various mechanisms for enhancing virulence, such as growth at 39°C, adaptation to stress, and capsule production; a remarkable amplification of ERG11 at the native and unlinked locus may provide stable resistance to fluconazole. Our data provide a deeper understanding of the microevolution of Cryptococcus species under pressure from antifungal chemotherapy and host immune responses. This investigation clearly suggests a promising strategy to identify novel targets for improved diagnosis, therapy, and prognosis.IMPORTANCE Opportunistic infections caused by species of the pathogenic yeast Cryptococcus lead to chronic meningoencephalitis and continue to ravage thousands of patients with HIV/AIDS. Despite receiving antifungal treatment, over 10% of patients develop recurrent disease. In this study, we collected isolates of Cryptococcus from cerebrospinal fluid specimens of 18 patients at the time of their diagnosis and when they relapsed several months later. We then sequenced and compared the genomic DNAs of each pair of initial and relapse isolates. We also tested the isolates for several key properties related to cryptococcal virulence as well as for their susceptibility to the antifungal drug fluconazole. These analyses revealed that the relapsing isolates manifested multiple genetic and chromosomal changes that affected a variety of genes implicated in the pathogenicity of Cryptococcus or resistance to fluconazole. This application of comparative genomics to serial clinical isolates provides a blueprint for identifying the mechanisms whereby pathogenic microbes adapt within patients to prolong disease.
Open Access
The Cryptococcus neoformans transcriptome at the site of human meningitis
(mBio, 2014-02-04) Chen, Yuan; Toffaletti, Dena L; Tenor, Jennifer L; Litvintseva, Anastasia P; Fang, Charles; Mitchell, Thomas G; McDonald, Tami R; Nielsen, Kirsten; Boulware, David R; Bicanic, Tihana; Perfect, John R
Cryptococcus neoformans is the leading cause of fungal meningitis worldwide. Previous studies have characterized the cryptococcal transcriptome under various stress conditions, but a comprehensive profile of the C. neoformans transcriptome in the human host has not been attempted. Here, we extracted RNA from yeast cells taken directly from the cerebrospinal fluid (CSF) of two AIDS patients with cryptococcal meningitis prior to antifungal therapy. The patients were infected with strains of C. neoformans var. grubii of molecular type VNI and VNII. Using RNA-seq, we compared the transcriptional profiles of these strains under three environmental conditions (in vivo CSF, ex vivo CSF, and yeast extract-peptone-dextrose [YPD]). Although we identified a number of differentially expressed genes, single nucleotide variants, and novel genes that were unique to each strain, the overall expression patterns of the two strains were similar under the same environmental conditions. Specifically, yeast cells obtained directly from each patient's CSF were more metabolically active than cells that were incubated ex vivo in CSF. Compared with growth in YPD, some genes were identified as significantly upregulated in both in vivo and ex vivo CSF, and they were associated with genes previously recognized for contributing to pathogenicity. For example, genes with known stress response functions, such as RIM101, ENA1, and CFO1, were regulated similarly in the two clinical strains. Conversely, many genes that were differentially regulated between the two strains appeared to be transporters. These findings establish a platform for further studies of how this yeast survives and produces disease. © 2014 Chen et al.