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Yang F, Berman J. Beyond resistance: antifungal heteroresistance and antifungal tolerance in fungal pathogens. Curr Opin Microbiol 2024; 78:102439. [PMID: 38401284 DOI: 10.1016/j.mib.2024.102439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 09/18/2023] [Accepted: 02/05/2024] [Indexed: 02/26/2024]
Abstract
Fungal infections are increasing globally, causing alarmingly high mortality and economic burden. In addition to antifungal resistance, other more subtle drug responses appear to increase the likelihood of treatment failures. These responses include heteroresistance and tolerance, terms that are more well-defined for antibacterial drugs, but are also evident in pathogenic fungi. Here, we compare these antifungal responses with similarly named antibacterial responses, and we review recent advances in how we understand the routes by which antifungal heteroresistance and tolerance emerge.
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Affiliation(s)
- Feng Yang
- Department of Pharmacy, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Judith Berman
- Shmunis School of Biomedical and Cancer Research, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
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2
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Feng Y, Lu H, Whiteway M, Jiang Y. Understanding fluconazole tolerance in Candida albicans: implications for effective treatment of candidiasis and combating invasive fungal infections. J Glob Antimicrob Resist 2023; 35:314-321. [PMID: 37918789 DOI: 10.1016/j.jgar.2023.10.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 10/07/2023] [Accepted: 10/22/2023] [Indexed: 11/04/2023] Open
Abstract
OBJECTIVES Fluconazole (FLC) tolerant phenotypes in Candida species contribute to persistent candidemia and the emergence of FLC resistance. Therefore, making FLC fungicidal and eliminating FLC tolerance are important for treating invasive fungal diseases (IFDs) caused by Candida species. However, the mechanisms of FLC tolerance in Candida species remain to be fully explored. METHODS This review discusses the high incidence of FLC tolerance in Candida species and the importance of successfully clearing FLC tolerance in treating candidiasis. We further define and characterize FLC tolerance in C. albicans. RESULTS This review identifies global factors affecting FLC tolerance and suggest that FLC tolerance is a strategy of C. albicans response to FLC damage whose mechanism differs from FLC resistance. CONCLUSIONS This review highlights the significance of the cell membrane and cell wall integrity in FLC tolerance, guiding approaches to combat IFDs caused by Candida species..
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Affiliation(s)
- Yanru Feng
- Department of Pharmacy, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Hui Lu
- Department of Pharmacy, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | | | - Yuanying Jiang
- Department of Pharmacy, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China.
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3
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Dumeaux V, Massahi S, Bettauer V, Mottola A, Dukovny A, Khurdia SS, Costa ACBP, Omran RP, Simpson S, Xie JL, Whiteway M, Berman J, Hallett MT. Candida albicans exhibits heterogeneous and adaptive cytoprotective responses to antifungal compounds. eLife 2023; 12:e81406. [PMID: 37888959 PMCID: PMC10699808 DOI: 10.7554/elife.81406] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Accepted: 10/26/2023] [Indexed: 10/28/2023] Open
Abstract
Candida albicans, an opportunistic human pathogen, poses a significant threat to human health and is associated with significant socio-economic burden. Current antifungal treatments fail, at least in part, because C. albicans can initiate a strong drug tolerance response that allows some cells to grow at drug concentrations above their minimal inhibitory concentration. To better characterize this cytoprotective tolerance program at the molecular single-cell level, we used a nanoliter droplet-based transcriptomics platform to profile thousands of individual fungal cells and establish their subpopulation characteristics in the absence and presence of antifungal drugs. Profiles of untreated cells exhibit heterogeneous expression that correlates with cell cycle stage with distinct metabolic and stress responses. At 2 days post-fluconazole exposure (a time when tolerance is measurable), surviving cells bifurcate into two major subpopulations: one characterized by the upregulation of genes encoding ribosomal proteins, rRNA processing machinery, and mitochondrial cellular respiration capacity, termed the Ribo-dominant (Rd) state; and the other enriched for genes encoding stress responses and related processes, termed the Stress-dominant (Sd) state. This bifurcation persists at 3 and 6 days post-treatment. We provide evidence that the ribosome assembly stress response (RASTR) is activated in these subpopulations and may facilitate cell survival.
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Affiliation(s)
- Vanessa Dumeaux
- Department of Anatomy and Cell Biology, Western University, London, Canada
| | - Samira Massahi
- Department of Biology, Concordia University, Montreal, Canada
| | - Van Bettauer
- Department of Computer Science and Software Engineering, Concordia University, Montreal, Canada
| | - Austin Mottola
- Shmunis School of Biomedical and Cancer Research, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv-Yafo, Israel
| | - Anna Dukovny
- Shmunis School of Biomedical and Cancer Research, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv-Yafo, Israel
| | | | | | | | - Shawn Simpson
- Department of Computer Science and Software Engineering, Concordia University, Montreal, Canada
| | - Jinglin Lucy Xie
- Department of Chemical and Systems Biology, Stanford University, Stanford, United States
| | | | - Judith Berman
- Shmunis School of Biomedical and Cancer Research, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv-Yafo, Israel
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4
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Chauvel M, Bachellier-Bassi S, Guérout AM, Lee KK, Maufrais C, Permal E, Da Fonseca JP, Znaidi S, Mazel D, Munro CA, d'Enfert C, Legrand M. High-throughput functional profiling of the human fungal pathogen Candida albicans genome. Res Microbiol 2023; 174:104025. [PMID: 36587858 DOI: 10.1016/j.resmic.2022.104025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 12/23/2022] [Accepted: 12/26/2022] [Indexed: 12/31/2022]
Abstract
Candida albicans is a major fungal pathogen of humans. Although its genome has been sequenced more than two decades ago, there are still over 4300 uncharacterized C. albicans genes. We previously generated an ORFeome as well as a collection of destination vectors to facilitate overexpression of C. albicans ORFs. Here, we report the construction of ∼2500 overexpression mutants and their evaluation by in vitro spotting on rich medium and in a liquid pool experiment in rich medium, allowing the identification of genes whose overexpression has a fitness cost. The candidates were further validated at the individual strain level. This new resource allows large-scale screens in different growth conditions to be performed routinely. Altogether, based on the concept of identifying functionally related genes by cluster analysis, the availability of this overexpression mutant collection will facilitate the characterization of gene functions in C. albicans.
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Affiliation(s)
- Murielle Chauvel
- Institut Pasteur, Université Paris Cité, INRAE USC2019, Unité Biologie et Pathogénicité Fongiques, F-75015 Paris, France.
| | - Sophie Bachellier-Bassi
- Institut Pasteur, Université Paris Cité, INRAE USC2019, Unité Biologie et Pathogénicité Fongiques, F-75015 Paris, France.
| | - Anne-Marie Guérout
- Institut Pasteur, Université Paris Cité, UMR3525 CNRS, Unité Plasticité du Génome Bactérien, F-75015 Paris, France.
| | - Keunsook K Lee
- Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK; NGeneBio, 307 Daerung Post-tower 1, 288 Digital-ro, Guro-gu, Seoul 08390, Republic of Korea.
| | - Corinne Maufrais
- Institut Pasteur, Université Paris Cité, INRAE USC2019, Unité Biologie et Pathogénicité Fongiques, F-75015 Paris, France; Institut Pasteur, Université Paris Cité, Hub de Bioinformatique, F-75015 Paris, France.
| | - Emmanuelle Permal
- Institut Pasteur, Université Paris Cité, INRAE USC2019, Unité Biologie et Pathogénicité Fongiques, F-75015 Paris, France; Institut Pasteur, Université Paris Cité, UMR3525 CNRS, Unité Plasticité du Génome Bactérien, F-75015 Paris, France; Institut Pasteur, Université Paris Cité, Hub de Bioinformatique, F-75015 Paris, France.
| | - Juliana Pipoli Da Fonseca
- Institut Pasteur, Université Paris Cité, Plate-forme Technologique Biomics, Centre de Ressources et Recherches Technologiques (C2RT), F-75015 Paris, France.
| | - Sadri Znaidi
- Institut Pasteur, Université Paris Cité, INRAE USC2019, Unité Biologie et Pathogénicité Fongiques, F-75015 Paris, France; Laboratoire de Microbiologie Moléculaire, Vaccinologie et Développement Biotechnologique, Institut Pasteur de Tunis, University of Tunis El Manar, Tunis-Belvédère, Tunisia.
| | - Didier Mazel
- Institut Pasteur, Université Paris Cité, UMR3525 CNRS, Unité Plasticité du Génome Bactérien, F-75015 Paris, France.
| | - Carol A Munro
- Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK.
| | - Christophe d'Enfert
- Institut Pasteur, Université Paris Cité, INRAE USC2019, Unité Biologie et Pathogénicité Fongiques, F-75015 Paris, France.
| | - Melanie Legrand
- Institut Pasteur, Université Paris Cité, INRAE USC2019, Unité Biologie et Pathogénicité Fongiques, F-75015 Paris, France.
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5
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Gervais NC, La Bella AA, Wensing LF, Sharma J, Acquaviva V, Best M, Cadena López RO, Fogal M, Uthayakumar D, Chavez A, Santiago-Tirado F, Flores-Mireles AL, Shapiro RS. Development and applications of a CRISPR activation system for facile genetic overexpression in Candida albicans. G3 (BETHESDA, MD.) 2023; 13:jkac301. [PMID: 36450451 PMCID: PMC9911074 DOI: 10.1093/g3journal/jkac301] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 11/02/2021] [Accepted: 11/04/2022] [Indexed: 12/02/2022]
Abstract
For the fungal pathogen Candida albicans, genetic overexpression readily occurs via a diversity of genomic alterations, such as aneuploidy and gain-of-function mutations, with important consequences for host adaptation, virulence, and evolution of antifungal drug resistance. Given the important role of overexpression on C. albicans biology, it is critical to develop and harness tools that enable the analysis of genes expressed at high levels in the fungal cell. Here, we describe the development, optimization, and application of a novel, single-plasmid-based CRISPR activation (CRISPRa) platform for targeted genetic overexpression in C. albicans, which employs a guide RNA to target an activator complex to the promoter region of a gene of interest, thus driving transcriptional expression of that gene. Using this system, we demonstrate the ability of CRISPRa to drive high levels of gene expression in C. albicans, and we assess optimal guide RNA targeting for robust and constitutive overexpression. We further demonstrate the specificity of the system via RNA sequencing. We highlight the application of CRISPR activation to overexpress genes involved in pathogenesis and drug susceptibility, and contribute toward the identification of novel phenotypes. Consequently, this tool will facilitate a broad range of applications for the study of C. albicans genetic overexpression.
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Affiliation(s)
- Nicholas C Gervais
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1H 5N4, Canada
| | - Alyssa A La Bella
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Lauren F Wensing
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1H 5N4, Canada
| | - Jehoshua Sharma
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1H 5N4, Canada
| | - Victoria Acquaviva
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1H 5N4, Canada
| | - Madison Best
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1H 5N4, Canada
| | | | - Meea Fogal
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1H 5N4, Canada
| | - Deeva Uthayakumar
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1H 5N4, Canada
- Present address: Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Alejandro Chavez
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
| | | | - Ana L Flores-Mireles
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Rebecca S Shapiro
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1H 5N4, Canada
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6
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Gow NAR, Johnson C, Berman J, Coste AT, Cuomo CA, Perlin DS, Bicanic T, Harrison TS, Wiederhold N, Bromley M, Chiller T, Edgar K. The importance of antimicrobial resistance in medical mycology. Nat Commun 2022; 13:5352. [PMID: 36097014 PMCID: PMC9466305 DOI: 10.1038/s41467-022-32249-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 07/22/2022] [Indexed: 01/08/2023] Open
Abstract
Prior to the SARS-CoV-2 pandemic, antibiotic resistance was listed as the major global health care priority. Some analyses, including the O'Neill report, have predicted that deaths due to drug-resistant bacterial infections may eclipse the total number of cancer deaths by 2050. Although fungal infections remain in the shadow of public awareness, total attributable annual deaths are similar to, or exceeds, global mortalities due to malaria, tuberculosis or HIV. The impact of fungal infections has been exacerbated by the steady rise of antifungal drug resistant strains and species which reflects the widespread use of antifungals for prophylaxis and therapy, and in the case of azole resistance in Aspergillus, has been linked to the widespread agricultural use of antifungals. This review, based on a workshop hosted by the Medical Research Council and the University of Exeter, illuminates the problem of antifungal resistance and suggests how this growing threat might be mitigated.
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Affiliation(s)
- Neil A R Gow
- MRC Centre for Medical Mycology, School of Biosciences, University of Exeter, Geoffrey Pope Building, Exeter, EX4 4QD, UK.
| | - Carolyn Johnson
- Medical Research Council, Polaris House, Swindon, SN2 1FL, UK.
| | - Judith Berman
- Shmunis School of Biomedical and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, 418 Britannia Building, Ramat Aviv, 69978, Israel
| | - Alix T Coste
- Microbiology Institute, University Hospital Lausanne, rue du Bugnon 48, 1011, Lausanne, Switzerland
| | - Christina A Cuomo
- (CAC) Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
| | - David S Perlin
- Center for Discovery and Innovation, Hackensack Meridian health, Nutley, NJ, 07110, USA
| | - Tihana Bicanic
- Institute of Infection and Immunity, St George's University of London, London, SW17 0RE, UK
- Clinical Academic Group in Infection, St George's University Hospitals NHS Foundation Trust, London, SW17 0QT, UK
| | - Thomas S Harrison
- MRC Centre for Medical Mycology, School of Biosciences, University of Exeter, Geoffrey Pope Building, Exeter, EX4 4QD, UK
- Institute of Infection and Immunity, St George's University of London, London, SW17 0RE, UK
- Clinical Academic Group in Infection, St George's University Hospitals NHS Foundation Trust, London, SW17 0QT, UK
| | - Nathan Wiederhold
- Department of Pathology and Laboratory Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Mike Bromley
- Manchester Fungal Infection Group, Division of Evolution, Infection, and Genomics, Faculty of Biology, Medicine and Health, University of Manchester, CTF Building, 46 Grafton Street, Manchester, M13 9NT, UK
| | - Tom Chiller
- Center for Disease Control and Prevention Mycotic Disease Branch 1600 Clifton Rd, MSC-09, Atlanta, 30333, GA, USA
| | - Keegan Edgar
- Center for Disease Control and Prevention Mycotic Disease Branch 1600 Clifton Rd, MSC-09, Atlanta, 30333, GA, USA
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7
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Kukurudz RJ, Chapel M, Wonitowy Q, Adamu Bukari AR, Sidney B, Sierhuis R, Gerstein AC. Acquisition of cross-azole tolerance and aneuploidy in Candida albicans strains evolved to posaconazole. G3 (BETHESDA, MD.) 2022; 12:jkac156. [PMID: 35881695 PMCID: PMC9434289 DOI: 10.1093/g3journal/jkac156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 06/13/2022] [Indexed: 12/30/2022]
Abstract
A number of in vitro studies have examined the acquisition of drug resistance to the triazole fluconazole, a first-line treatment for many Candida infections. Much less is known about posaconazole, a newer triazole. We conducted the first in vitro experimental evolution of replicates from 8 diverse strains of Candida albicans in a high level of the fungistatic drug posaconazole. Approximately half of the 132 evolved replicates survived 50 generations of evolution, biased toward some of the strain backgrounds. We found that although increases in drug resistance were rare, increases in drug tolerance (the slow growth of a subpopulation of cells in a level of drug above the resistance level) were common across strains. We also found that adaptation to posaconazole resulted in widespread cross-tolerance to other azole drugs. Widespread aneuploidy was observed in evolved replicates from some strain backgrounds. Trisomy of at least one of chromosomes 3, 6, and R was identified in 11 of 12 whole-genome sequenced evolved SC5314 replicates. These findings document rampant evolved cross-tolerance among triazoles and highlight that increases in drug tolerance can evolve independently of drug resistance in a diversity of C. albicans strain backgrounds.
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Affiliation(s)
- Rebekah J Kukurudz
- Department of Microbiology, The University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Madison Chapel
- Department of Microbiology, The University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Quinn Wonitowy
- Department of Microbiology, The University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | | | - Brooke Sidney
- Department of Microbiology, The University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Riley Sierhuis
- Department of Microbiology, The University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Aleeza C Gerstein
- Department of Microbiology, The University of Manitoba, Winnipeg, MB R3T 2N2, Canada
- Department of Statistics, The University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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8
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Response and regulatory mechanisms of heat resistance in pathogenic fungi. Appl Microbiol Biotechnol 2022; 106:5415-5431. [PMID: 35941254 PMCID: PMC9360699 DOI: 10.1007/s00253-022-12119-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 08/01/2022] [Accepted: 08/02/2022] [Indexed: 12/03/2022]
Abstract
Abstract Both the increasing environmental temperature in nature and the defensive body temperature response to pathogenic fungi during mammalian infection cause heat stress during the fungal existence, reproduction, and pathogenic infection. To adapt and respond to the changing environment, fungi initiate a series of actions through a perfect thermal response system, conservative signaling pathways, corresponding transcriptional regulatory system, corresponding physiological and biochemical processes, and phenotypic changes. However, until now, accurate response and regulatory mechanisms have remained a challenge. Additionally, at present, the latest research progress on the heat resistance mechanism of pathogenic fungi has not been summarized. In this review, recent research investigating temperature sensing, transcriptional regulation, and physiological, biochemical, and morphological responses of fungi in response to heat stress is discussed. Moreover, the specificity thermal adaptation mechanism of pathogenic fungi in vivo is highlighted. These data will provide valuable knowledge to further understand the fungal heat adaptation and response mechanism, especially in pathogenic heat-resistant fungi. Key points • Mechanisms of fungal perception of heat pressure are reviewed. • The regulatory mechanism of fungal resistance to heat stress is discussed. • The thermal adaptation mechanism of pathogenic fungi in the human body is highlighted.
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9
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Aspergillus terreus and the Interplay with Amphotericin B: from Resistance to Tolerance? Antimicrob Agents Chemother 2022; 66:e0227421. [PMID: 35254091 PMCID: PMC9017323 DOI: 10.1128/aac.02274-21] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Aspergillus terreus is an opportunistic causative agent of invasive aspergillosis and, in most cases, it is refractory to amphotericin B (AMB) therapy. Notably, AMB-susceptible Aspergillus terreus sensu stricto (s.s.) representatives exist which are also associated with poor clinical outcomes. Such findings may be attributable to drug tolerance, which is not detectable by antifungal susceptibility testing. Here, we tested in vitro antifungal susceptibility (AFST) and the fungicidal activity of AMB against 100 clinical isolates of A. terreus species complex in RPMI 1640 and antibiotic medium 3 (AM3). MICs ranged from 0.5 to 16 μg/mL for RPMI 1640 and from 1 to >16 mg/L for AM3. AMB showed medium-dependent activity, with fungicidal effects only in antibiotic medium 3, not in RPMI 1640. Furthermore, the presence of AMB-tolerant phenotypes of A. terreus has been examined by assessing the minimum duration for killing 99% of the population (MDK99) and evaluating the data obtained in a Galleria mellonella infection model. A time-kill curve analysis revealed that A. terreus with AMB MICs of ≤1 mg/L (susceptible range) displayed AMB-tolerant phenotypes, exhibiting MDK99s at 18 and 36 h, respectively. Survival rates of infected G. mellonella highlighted that AMB was effective against susceptible A. terreus isolates, but not against tolerant or resistant isolates. Our analysis reveals that A. terreus isolates which are defined as susceptible based on MIC may comprise tolerant phenotypes, which may, in turn, explain the worse outcome of AMB therapy for phenotypically susceptible isolates.
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10
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Murphy SE, Bicanic T. Drug Resistance and Novel Therapeutic Approaches in Invasive Candidiasis. Front Cell Infect Microbiol 2022; 11:759408. [PMID: 34970504 PMCID: PMC8713075 DOI: 10.3389/fcimb.2021.759408] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 11/08/2021] [Indexed: 12/12/2022] Open
Abstract
Candida species are the leading cause of invasive fungal infections worldwide and are associated with acute mortality rates of ~50%. Mortality rates are further augmented in the context of host immunosuppression and infection with drug-resistant Candida species. In this review, we outline antifungal drugs already in clinical use for invasive candidiasis and candidaemia, their targets and mechanisms of resistance in clinically relevant Candida species, encompassing not only classical resistance, but also heteroresistance and tolerance. We describe novel antifungal agents and targets in pre-clinical and clinical development, including their spectrum of activity, antifungal target, clinical trial data and potential in treatment of drug-resistant Candida. Lastly, we discuss the use of combination therapy between conventional and repurposed agents as a potential strategy to combat the threat of emerging resistance in Candida.
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Affiliation(s)
- Sarah E Murphy
- Institute of Infection & Immunity, St George's University of London, London, United Kingdom
| | - Tihana Bicanic
- Institute of Infection & Immunity, St George's University of London, London, United Kingdom.,Clinical Academic Group in Infection and Immunity, St. George's University Hospital National Health Service (NHS) Foundation Trust, London, United Kingdom
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11
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Rai LS, van Wijlick L, Chauvel M, d'Enfert C, Legrand M, Bachellier-Bassi S. Overexpression approaches to advance understanding of Candida albicans. Mol Microbiol 2021; 117:589-599. [PMID: 34569668 PMCID: PMC9298300 DOI: 10.1111/mmi.14818] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 09/23/2021] [Indexed: 12/15/2022]
Abstract
Candida albicans is an opportunistic fungal pathogen that is responsible for infections linked to high mortality. Loss‐of‐function approaches, taking advantage of gene knockouts or inducible down‐regulation, have been successfully used in this species in order to understand gene function. However, overexpression of a gene provides an alternative, powerful tool to elucidate gene function and identify novel phenotypes. Notably, overexpression can identify pathway components that might remain undetected using loss‐of‐function approaches. Several repressible or inducible promoters have been developed which allow to shut off or turn on the expression of a gene in C. albicans upon growth in the presence of a repressor or inducer. In this review, we summarize recent overexpression approaches used to study different aspects of C. albicans biology, including morphogenesis, biofilm formation, drug tolerance, and commensalism.
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Affiliation(s)
- Laxmi Shanker Rai
- Unité Biologie et Pathogénicité Fongiques, Institut Pasteur, Université de Paris, INRAE, USC2019, Paris, France
| | - Lasse van Wijlick
- Unité Biologie et Pathogénicité Fongiques, Institut Pasteur, Université de Paris, INRAE, USC2019, Paris, France
| | - Murielle Chauvel
- Unité Biologie et Pathogénicité Fongiques, Institut Pasteur, Université de Paris, INRAE, USC2019, Paris, France
| | - Christophe d'Enfert
- Unité Biologie et Pathogénicité Fongiques, Institut Pasteur, Université de Paris, INRAE, USC2019, Paris, France
| | - Mélanie Legrand
- Unité Biologie et Pathogénicité Fongiques, Institut Pasteur, Université de Paris, INRAE, USC2019, Paris, France
| | - Sophie Bachellier-Bassi
- Unité Biologie et Pathogénicité Fongiques, Institut Pasteur, Université de Paris, INRAE, USC2019, Paris, France
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12
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Abstract
Candida albicans is a prevalent opportunistic human fungal pathogen for which treatment is limited to only four main classes of antifungal drugs, with the azole and echinocandin classes being used most frequently. Drug tolerance, the ability of some cells to grow slowly in supra-MIC drug concentrations, decreases the number of available treatment options. Here, we investigated factors affecting tolerance and resistance to ketoconazole in C. albicans. We found both temperature and the composition of growth medium significantly affected tolerance with little effect on resistance. In deletion analysis of known efflux pump genes, CDR1 was partially required for azole tolerance, while CDR2 and MDR1 were dispensable. Tolerance also required Hsp90 and calcineurin components; CRZ1, which encodes a transcription factor downstream of calcineurin, was required only partially. Deletion of VMA11, which encodes a vacuolar ATPase subunit, and concanamycin A, a V-ATPase inhibitor, abolished tolerance, indicating the importance of vacuolar energy transactions in tolerance. Thus, tolerance to ketoconazole is regulated by multiple factors, including physiological and genetic mechanisms. IMPORTANCE Due to the ever-expanding range of invasive medical procedures and treatments, invasive fungal infections now pose a serious global threat to many people living in an immunocompromised status. Like humans, fungi are eukaryotic, which significantly limits the number of unique antifungal targets; the current arsenal of antifungal agents is limited to just three frontline drug classes. Additional treatment complexities result from the development of drug tolerance and resistance, which further narrows therapeutic options; however, the difference between tolerance and resistance remains largely unknown. This study demonstrates that tolerance and resistance are regulated by multiple genetic and physiological factors. It is prudent to note that some factors affect tolerance only, while other factors affect both tolerance and resistance. The complex underlying mechanisms of these drug responses are highlighted by the fact that there are both shared and distinct mechanisms that regulate tolerance and resistance.
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