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Chang YC, Davis MJ, Kwon-Chung KJ. Determination of Ploidy Levels and Nuclear DNA Content in Cryptococcus neoformans by Flow Cytometry: Drawbacks with Variability. J Fungi (Basel) 2024; 10:296. [PMID: 38667967 PMCID: PMC11051530 DOI: 10.3390/jof10040296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 04/02/2024] [Accepted: 04/15/2024] [Indexed: 04/28/2024] Open
Abstract
Flow cytometry is commonly employed for ploidy determination and cell cycle analysis in cryptococci. The cells are subjected to fixation and staining with DNA-binding fluorescent dyes, most commonly with propidium iodide (PI), before undergoing flow cytometric analysis. In ploidy determination, cell populations are classified according to variations in DNA content, as evidenced by the fluorescence intensity of stained cells. As reported in Saccharomyces cerevisiae, we found drawbacks with PI staining that confounded the accurate analysis of ploidy by flow cytometry when the size of the cryptococci changed significantly. However, the shift in the fluorescence intensity, unrelated to ploidy changes in cells with increased size, could be accurately interpreted by applying the ImageStream system. SYTOX Green or SYBR Green I, reported to enable DNA analysis with a higher accuracy than PI in S. cerevisiae, were nonspecific for nuclear DNA staining in cryptococci. Until dyes or methods capable of reducing the variability inherent in the drastic changes in cell size or shape become available, PI appears to remain the most reliable method for cell cycle or ploidy analysis in Cryptococcus.
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Affiliation(s)
| | | | - Kyung J. Kwon-Chung
- Molecular Microbiology Section, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA; (Y.C.C.)
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2
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Kassaza K, Wasswa F, Nielsen K, Bazira J. Cryptococcus neoformans Genotypic Diversity and Disease Outcome among HIV Patients in Africa. J Fungi (Basel) 2022; 8:jof8070734. [PMID: 35887489 PMCID: PMC9325144 DOI: 10.3390/jof8070734] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 06/24/2022] [Accepted: 07/06/2022] [Indexed: 11/16/2022] Open
Abstract
Cryptococcal meningoencephalitis, a disease with poor patient outcomes, remains the most prevalent invasive fungal infection worldwide, accounting for approximately 180,000 deaths each year. In several areas of sub-Saharan Africa with the highest HIV prevalence, cryptococcal meningitis is the leading cause of community-acquired meningitis, with a high mortality among HIV-infected individuals. Recent studies show that patient disease outcomes are impacted by the genetics of the infecting isolate. Yet, there is still limited knowledge of how these genotypic variations contribute to clinical disease outcome. Further, it is unclear how the genetic heterogeneity of C. neoformans and the extensive phenotypic variation observed between and within isolates affects infection and disease. In this review, we discuss current knowledge of how various genotypes impact disease progression and patient outcome in HIV-positive populations in sub-Saharan African, a setting with a high burden of cryptococcosis.
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Affiliation(s)
- Kennedy Kassaza
- Department of Microbiology and Parasitology, Mbarara University of Science and Technology, Mbarara P.O. Box 1410, Uganda; (K.K.); (F.W.)
| | - Fredrickson Wasswa
- Department of Microbiology and Parasitology, Mbarara University of Science and Technology, Mbarara P.O. Box 1410, Uganda; (K.K.); (F.W.)
| | - Kirsten Nielsen
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN 55455, USA
- Correspondence: (K.N.); (J.B.)
| | - Joel Bazira
- Department of Microbiology and Parasitology, Mbarara University of Science and Technology, Mbarara P.O. Box 1410, Uganda; (K.K.); (F.W.)
- Correspondence: (K.N.); (J.B.)
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3
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Berguson HP, Caulfield LW, Price MS. Influence of Pathogen Carbon Metabolism on Interactions With Host Immunity. Front Cell Infect Microbiol 2022; 12:861405. [PMID: 35372116 PMCID: PMC8968422 DOI: 10.3389/fcimb.2022.861405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 02/24/2022] [Indexed: 11/22/2022] Open
Abstract
Cryptococcus neoformans is a ubiquitous opportunistic fungal pathogen typically causing disease in immunocompromised individuals and is globally responsible for about 15% of AIDS-related deaths annually. C. neoformans first causes pulmonary infection in the host and then disseminates to the brain, causing meningoencephalitis. The yeast must obtain and metabolize carbon within the host in order to survive in the central nervous system and cause disease. Communication between pathogen and host involves recognition of multiple carbon-containing compounds on the yeast surface: polysaccharide capsule, fungal cell wall, and glycosylated proteins comprising the major immune modulators. The structure and function of polysaccharide capsule has been studied for the past 70 years, emphasizing its role in virulence. While protected by the capsule, fungal cell wall has likewise been a focus of study for several decades for its role in cell integrity and host recognition. Associated with both of these major structures are glycosylated proteins, which exhibit known immunomodulatory effects. While many studies have investigated the role of carbon metabolism on virulence and survival within the host, the precise mechanism(s) affecting host-pathogen communication remain ill-defined. This review summarizes the current knowledge on mutants in carbon metabolism and their effect on the host immune response that leads to changes in pathogen recognition and virulence. Understanding these critical interactions will provide fresh perspectives on potential treatments and the natural history of cryptococcal disease.
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Affiliation(s)
- Hannah P. Berguson
- Department of Anatomical Sciences, Liberty University College of Osteopathic Medicine, Lynchburg, VA, United States
| | - Lauren W. Caulfield
- Department of Biology and Chemistry, Liberty University, Lynchburg, VA, United States
| | - Michael S. Price
- Department of Molecular and Cellular Sciences, Liberty University College of Osteopathic Medicine, Lynchburg, VA, United States
- Department of Medicine, Duke University School of Medicine, Durham, NC, United States
- *Correspondence: Michael S. Price,
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4
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Mitotic Recombination and Adaptive Genomic Changes in Human Pathogenic Fungi. Genes (Basel) 2019; 10:genes10110901. [PMID: 31703352 PMCID: PMC6895784 DOI: 10.3390/genes10110901] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 11/01/2019] [Accepted: 11/05/2019] [Indexed: 12/11/2022] Open
Abstract
Genome rearrangements and ploidy alterations are important for adaptive change in the pathogenic fungal species Candida and Cryptococcus, which propagate primarily through clonal, asexual reproduction. These changes can occur during mitotic growth and lead to enhanced virulence, drug resistance, and persistence in chronic infections. Examples of microevolution during the course of infection were described in both human infections and mouse models. Recent discoveries defining the role of sexual, parasexual, and unisexual cycles in the evolution of these pathogenic fungi further expanded our understanding of the diversity found in and between species. During mitotic growth, damage to DNA in the form of double-strand breaks (DSBs) is repaired, and genome integrity is restored by the homologous recombination and non-homologous end-joining pathways. In addition to faithful repair, these pathways can introduce minor sequence alterations at the break site or lead to more extensive genetic alterations that include loss of heterozygosity, inversions, duplications, deletions, and translocations. In particular, the prevalence of repetitive sequences in fungal genomes provides opportunities for structural rearrangements to be generated by non-allelic (ectopic) recombination. In this review, we describe DSB repair mechanisms and the types of resulting genome alterations that were documented in the model yeast Saccharomyces cerevisiae. The relevance of similar recombination events to stress- and drug-related adaptations and in generating species diversity are discussed for the human fungal pathogens Candida albicans and Cryptococcus neoformans.
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Kassi FK, Drakulovski P, Bellet V, Roger F, Chabrol A, Krasteva D, Doumbia A, Landman R, Kakou A, Reynes J, Delaporte E, Menan HEI, Bertout S. Cryptococcus genetic diversity and mixed infections in Ivorian HIV patients: A follow up study. PLoS Negl Trop Dis 2019; 13:e0007812. [PMID: 31738768 PMCID: PMC6886875 DOI: 10.1371/journal.pntd.0007812] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 12/02/2019] [Accepted: 09/26/2019] [Indexed: 01/07/2023] Open
Abstract
Genetic diversity analyses were performed by sero-genotyping and multi-locus sequence typing on 252 cryptococcal isolates from 13 HIV-positive Ivorian patients followed-up for cryptococcal meningitis. Antifungal susceptibility analyses were performed according to the CLSI M27A3 method. The majority (67.8%) of the isolates belonged to the Cryptococcus neoformans (serotype A) species complex, with 93% being VNI and 7% being VNII. Cryptococcus deuterogattii VGII (serotype B) represented 16.7% of the strains, while C. neoformans/C. deneoformans VNIII (serotype AD) hybrids accounted for 15.1% of the strains. One strain (0.4%) was not identifiable. Nine different sequence types (STs 5, 6, 23, 40, 93, 207, 311, and a new ST; 555) were identified in the C. neoformans population, while the C. deuterogattii population comprised the single ST 173. The distribution of the strains showed that, while the majority of patients (9/13) harboured a single sequence type, 4 patients showed mixed infections. These patients experienced up to 4 shifts in strain content either at the species and/or ST level during their follow-up. This evolution of diversity over time led to the co-existence of up to 3 different Cryptococcus species and 4 different ST within the same individual during the course of infection. Susceptibility testing showed that all strains were susceptible to amphotericin B while 3.6% of them had a none-wild type phenotype to 5-flucytosine. Concerning fluconazole, 2.9% of C.neoformans serotype A strains and 2.4% of C. deuterogattii had also respectively a none-wild type phenotype to this molecule. All C. neoformans x C. deneoformans serotype AD hybrids had however a wild type phenotype to fluconazole. The present study showed that mixed infections exist and could be of particular importance for care outcomes. Indeed, (i) the different Cryptococcus species are known to exhibit different virulence and different susceptibility patterns to antifungal drugs and (ii) the strains genetic diversity within the samples may influence the susceptibility to antifungal treatment.
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Affiliation(s)
- Fulgence Kondo Kassi
- Université Félix Houphouet-Boigny, Unité des Sciences Pharmaceutiques et Biologiques, Abidjan, Côte d’Ivoire
| | - Pascal Drakulovski
- Laboratoire de Parasitologie et Mycologie Médicale, IRD UMI 233, INSERM U1175, Université de Montpellier, Unité TransVIHMI, Montpellier, France
| | - Virginie Bellet
- Laboratoire de Parasitologie et Mycologie Médicale, IRD UMI 233, INSERM U1175, Université de Montpellier, Unité TransVIHMI, Montpellier, France
| | - Frédéric Roger
- Laboratoire de Parasitologie et Mycologie Médicale, IRD UMI 233, INSERM U1175, Université de Montpellier, Unité TransVIHMI, Montpellier, France
| | - Amélie Chabrol
- Service de Maladies Infectieuses et Tropicales, CH Sud Francilien, Corbeil, France
| | - Donika Krasteva
- Laboratoire de Parasitologie et Mycologie Médicale, IRD UMI 233, INSERM U1175, Université de Montpellier, Unité TransVIHMI, Montpellier, France
| | - Adama Doumbia
- Université Félix Houphouet-Boigny, Unité des Sciences Pharmaceutiques et Biologiques, Abidjan, Côte d’Ivoire
| | - Roland Landman
- Institut de Médecine et Epidémiologie Appliquée (IMEA), Fondation Léon M’Ba, Paris, France
| | - Aka Kakou
- Service des Maladies Infectieuses et Tropicales, CHU Treichville, Abidjan, Côte d’Ivoire
| | - Jacques Reynes
- CHU Gui de Chauliac, Service des Maladies Infectieuses et Tropicales, IRD UMI 233, INSERM U1175, Université de Montpellier, Unité TransVIHMI, Montpellier, France
| | - Eric Delaporte
- TransVIHMI/INSERM1175, Institut de Recherche pour le Développement (IRD) and University of Montpellier, Montpellier, France
| | - Hervé Eby Ignace Menan
- Diagnostic and Research Center on AIDS and Other Infectious Diseases (CeDReS), Abidjan, Côte d'Ivoire
| | - Sébastien Bertout
- Laboratoire de Parasitologie et Mycologie Médicale, IRD UMI 233, INSERM U1175, Université de Montpellier, Unité TransVIHMI, Montpellier, France
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6
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Buscaino A. Chromatin-Mediated Regulation of Genome Plasticity in Human Fungal Pathogens. Genes (Basel) 2019; 10:E855. [PMID: 31661931 PMCID: PMC6896017 DOI: 10.3390/genes10110855] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/18/2019] [Accepted: 10/25/2019] [Indexed: 12/20/2022] Open
Abstract
Human fungal pathogens, such as Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans, are a public health problem, causing millions of infections and killing almost half a million people annually. The ability of these pathogens to colonise almost every organ in the human body and cause life-threating infections relies on their capacity to adapt and thrive in diverse hostile host-niche environments. Stress-induced genome instability is a key adaptive strategy used by human fungal pathogens as it increases genetic diversity, thereby allowing selection of genotype(s) better adapted to a new environment. Heterochromatin represses gene expression and deleterious recombination and could play a key role in modulating genome stability in response to environmental changes. However, very little is known about heterochromatin structure and function in human fungal pathogens. In this review, I use our knowledge of heterochromatin structure and function in fungal model systems as a road map to review the role of heterochromatin in regulating genome plasticity in the most common human fungal pathogens: Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans.
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Affiliation(s)
- Alessia Buscaino
- University of Kent, School of Biosciences, Kent Fungal Group, Canterbury Kent CT2 7NJ, UK.
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7
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Bravo Ruiz G, Ross ZK, Holmes E, Schelenz S, Gow NAR, Lorenz A. Rapid and extensive karyotype diversification in haploid clinical Candida auris isolates. Curr Genet 2019; 65:1217-1228. [PMID: 31020384 PMCID: PMC6744574 DOI: 10.1007/s00294-019-00976-w] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 04/09/2019] [Accepted: 04/15/2019] [Indexed: 11/30/2022]
Abstract
Candida auris is a newly emerged pathogenic microbe, having been identified as a medically relevant fungus as recently as 2009. It is one of the most drug-resistant yeast species known to date and its emergence and population structure are unusual. Because of its recent emergence, we are largely ignorant about fundamental aspects of its general biology, life cycle, and population dynamics. Here, we report the karyotype variability of 26 C. auris strains representing the four main clades. We demonstrate that all strains are haploid and have a highly plastic karyotype containing five to seven chromosomes, which can undergo marked alterations within a short time frame when the fungus is put under genotoxic, heat, or osmotic stress. No simple correlation was found between karyotype pattern, drug resistance, and clade affiliation indicating that karyotype heterogeneity is rapidly evolving. As with other Candida species, these marked karyotype differences between isolates are likely to have an important impact on pathogenic traits of C. auris.
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Affiliation(s)
- Gustavo Bravo Ruiz
- Institute of Medical Sciences (IMS), University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Zoe K Ross
- Institute of Medical Sciences (IMS), University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
- MRC Centre for Medical Mycology, University of Aberdeen, Aberdeen, UK
| | - Eilidh Holmes
- Institute of Medical Sciences (IMS), University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Silke Schelenz
- Department of Microbiology, Royal Brompton Hospital, London, UK
| | - Neil A R Gow
- Institute of Medical Sciences (IMS), University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
- MRC Centre for Medical Mycology, University of Aberdeen, Aberdeen, UK
- School of Biosciences, University of Exeter, Exeter, UK
| | - Alexander Lorenz
- Institute of Medical Sciences (IMS), University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
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8
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Wertheimer NB, Stone N, Berman J. Ploidy dynamics and evolvability in fungi. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0461. [PMID: 28080987 PMCID: PMC5095540 DOI: 10.1098/rstb.2015.0461] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2016] [Indexed: 12/12/2022] Open
Abstract
Rapid responses to acute stresses are essential for stress survival and are critical to the ability of fungal pathogens to adapt to new environments or hosts. The rapid emergence of drug resistance is used as a model for how fungi adapt and survive stress conditions that inhibit the growth of progenitor cells. Aneuploidy and loss of heterozygosity (LOH), which are large-scale genome shifts involving whole chromosomes or chromosome arms, occur at higher frequency than point mutations and have the potential to mediate stress survival. Furthermore, the stress of exposure to an antifungal drug can induce elevated levels of LOH and can promote the formation of aneuploids. This occurs via mitotic defects that first produce tetraploid progeny with extra spindles, followed by chromosome mis-segregation. Thus, drug exposure induces elevated levels of aneuploidy, which can alter the copy number of genes that improve survival in a given stress or drug. Selection then acts to increase the proportion of adaptive aneuploids in the population. Because aneuploidy is a common property of many pathogenic fungi, including those posing emerging threats to plants, animals and humans, we propose that aneuploid formation and LOH often accompanying it contribute to the rapid generation of diversity that can facilitate the emergence of fungal pathogens to new environmental niches and/or new hosts, as well as promote antifungal drug resistance that makes emerging fungal infections ever more difficult to contain.This article is part of the themed issue 'Tackling emerging fungal threats to animal health, food security and ecosystem resilience'.
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Affiliation(s)
- Noa Blutraich Wertheimer
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Britannia 418, Ramat Aviv, Israel
| | - Neil Stone
- Institute of Infection and Immunity, St George's, University of London, London SW17 0RE, UK
| | - Judith Berman
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Britannia 418, Ramat Aviv, Israel
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9
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Arras SDM, Chitty JL, Wizrah MSI, Erpf PE, Schulz BL, Tanurdzic M, Fraser JA. Sirtuins in the phylum Basidiomycota: A role in virulence in Cryptococcus neoformans. Sci Rep 2017; 7:46567. [PMID: 28429797 PMCID: PMC5399365 DOI: 10.1038/srep46567] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 03/17/2017] [Indexed: 02/07/2023] Open
Abstract
Virulence of Cryptococcus neoformans is regulated by a range of transcription factors, and is also influenced by the acquisition of adaptive mutations during infection. Beyond the temporal regulation of virulence factor production by transcription factors and these permanent microevolutionary changes, heritable epigenetic modifications such as histone deacetylation may also play a role during infection. Here we describe the first comprehensive analysis of the sirtuin class of NAD+ dependent histone deacetylases in the phylum Basidiomycota, identifying five sirtuins encoded in the C. neoformans genome. Each sirtuin gene was deleted and a wide range of phenotypic tests performed to gain insight into the potential roles they play. Given the pleiotropic nature of sirtuins in other species, it was surprising that only two of the five deletion strains revealed mutant phenotypes in vitro. However, cryptic consequences of the loss of each sirtuin were identified through whole cell proteomics, and mouse infections revealed a role in virulence for SIR2, HST3 and HST4. The most intriguing phenotype was the repeated inability to complement mutant phenotypes through the reintroduction of the wild-type gene. These data support the model that regulation of sirtuin activity may be employed to enable a drastic alteration of the epigenetic landscape and virulence of C. neoformans.
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Affiliation(s)
- Samantha D M Arras
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Jessica L Chitty
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Maha S I Wizrah
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Paige E Erpf
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Benjamin L Schulz
- School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Milos Tanurdzic
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - James A Fraser
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
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Microevolution of Serial Clinical Isolates of Cryptococcus neoformans var. grubii and C. gattii. mBio 2017; 8:mBio.00166-17. [PMID: 28270580 PMCID: PMC5340869 DOI: 10.1128/mbio.00166-17] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
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. 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.
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11
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Bouklas T, Fries BC. Aging: an emergent phenotypic trait that contributes to the virulence of Cryptococcus neoformans. Future Microbiol 2015; 10:191-7. [PMID: 25689531 DOI: 10.2217/fmb.14.124] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The pathogenic fungus, Cryptococcus neoformans, is known to undergo phenotypic variation, which affects its virulence in the host. Recent investigations on C. neoformans cells in humans have validated the concept that phenotypic variation is present and relevant for the outcome of chronic cryptococcosis. The C. neoformans capsule is not the only trait that varies among strains. An emerging variant is the "old cell phenotype" generated when C. neoformans undergoes replicative aging. This phenotype, which other than larger size also exhibits a thickened cell wall, inhibits phagocytosis and killing by antifungals in vitro. In concert with the finding that old cells accumulate in vivo, this emergent trait could have significant impact on cryptococcal virulence and infection, and contribute to treatment failure.
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Affiliation(s)
- Tejas Bouklas
- Division of Infectious Diseases, Department of Medicine, Health Sciences Center T15-080, Stony Brook University Medical Center, Stony Brook, NY 11794-8153, USA
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12
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Beardsley J, Thanh LT, Day J. A Model CNS Fungal Infection: Cryptococcal Meningitis. CURRENT CLINICAL MICROBIOLOGY REPORTS 2015. [DOI: 10.1007/s40588-015-0016-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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13
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Affiliation(s)
- Rebecca S. Shapiro
- The Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- Institute of Medical Engineering and Science, Department of Biological Engineering, and Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Department of Biomedical Engineering and Center of Synthetic Biology, Boston University, Boston, Massachusetts, United States of America
- * E-mail:
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14
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Chitty JL, Fraser JA. Rethinking the targets for antifungal development. MICROBIOLOGY AUSTRALIA 2015. [DOI: 10.1071/ma15028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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15
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Bouklas T, Fries BC. Aging as an emergent factor that contributes to phenotypic variation in Cryptococcus neoformans. Fungal Genet Biol 2014; 78:59-64. [PMID: 25307541 DOI: 10.1016/j.fgb.2014.10.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 09/26/2014] [Accepted: 10/02/2014] [Indexed: 12/15/2022]
Abstract
Cryptococcus neoformans, similar to other eukaryotes, undergoes replicative aging. Replicative life spans have been determined for clinical C. neoformans strains, and although they are a reproducible trait, life spans vary considerably among strains. C. neoformans has been proposed as an ideal model organism to investigate the contribution of replicative aging in a fungal pathogen population to emerging phenotypic variation during chronic cryptococcal infections. C. neoformans cells of advanced generational age manifest a distinct phenotype; specifically, a larger cell size, a thicker cell wall, drug resistance, as well as resistance to hydrogen peroxide-mediated killing. Consequently, old cells are selected in the host environment during chronic infection and aging could be an unanticipated mechanism of pathogen adaptation that contributes to persistent disease. Aging as a natural process of phenotypic variation should be further studied as it likely is also relevant for other eukaryotic pathogen populations that undergo asymmetric replicative aging.
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Affiliation(s)
- Tejas Bouklas
- Department of Medicine (Division of Infectious Diseases), Stony Brook University, Stony Brook, NY, USA
| | - Bettina C Fries
- Department of Medicine (Division of Infectious Diseases), Stony Brook University, Stony Brook, NY, USA; Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA.
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