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Ahmady L, Gothwal M, Mukkoli MM, Bari VK. Antifungal drug resistance in Candida: a special emphasis on amphotericin B. APMIS 2024; 132:291-316. [PMID: 38465406 DOI: 10.1111/apm.13389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 02/12/2024] [Indexed: 03/12/2024]
Abstract
Invasive fungal infections in humans caused by several Candida species, increased considerably in immunocompromised or critically ill patients, resulting in substantial morbidity and mortality. Candida albicans is the most prevalent species, although the frequency of these organisms varies greatly according to geographic region. Infections with C. albicans and non-albicans Candida species have become more common, especially in the past 20 years, as a result of aging, immunosuppressive medication use, endocrine disorders, malnourishment, extended use of medical equipment, and an increase in immunogenic diseases. Despite C. albicans being the species most frequently associated with human infections, C. glabrata, C. parapsilosis, C. tropicalis, and C. krusei also have been identified. Several antifungal drugs with different modes of action are approved for use in clinical settings to treat fungal infections. However, due to the common eukaryotic structure of humans and fungi, only a limited number of antifungal drugs are available for therapeutic use. Furthermore, drug resistance in Candida species has emerged as a result of the growing use of currently available antifungal drugs against fungal infections. Amphotericin B (AmB), a polyene class of antifungal drugs, is mainly used for the treatment of serious systemic fungal infections. AmB interacts with fungal plasma membrane ergosterol, triggering cellular ion leakage via pore formation, or extracting the ergosterol from the plasma membrane inducing cellular death. AmB resistance is primarily caused by changes in the content or structure of ergosterol. This review summarizes the antifungal drug resistance exhibited by Candida species, with a special focus on AmB.
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Affiliation(s)
- Lailema Ahmady
- Department of Biochemistry, School of Basic Sciences, Central University of Punjab, Bathinda, India
| | - Manisha Gothwal
- Department of Biochemistry, School of Basic Sciences, Central University of Punjab, Bathinda, India
| | | | - Vinay Kumar Bari
- Department of Biochemistry, School of Basic Sciences, Central University of Punjab, Bathinda, India
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Czajka KM, Venkataraman K, Brabant-Kirwan D, Santi SA, Verschoor C, Appanna VD, Singh R, Saunders DP, Tharmalingam S. Molecular Mechanisms Associated with Antifungal Resistance in Pathogenic Candida Species. Cells 2023; 12:2655. [PMID: 37998390 PMCID: PMC10670235 DOI: 10.3390/cells12222655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 11/14/2023] [Accepted: 11/17/2023] [Indexed: 11/25/2023] Open
Abstract
Candidiasis is a highly pervasive infection posing major health risks, especially for immunocompromised populations. Pathogenic Candida species have evolved intrinsic and acquired resistance to a variety of antifungal medications. The primary goal of this literature review is to summarize the molecular mechanisms associated with antifungal resistance in Candida species. Resistance can be conferred via gain-of-function mutations in target pathway genes or their transcriptional regulators. Therefore, an overview of the known gene mutations is presented for the following antifungals: azoles (fluconazole, voriconazole, posaconazole and itraconazole), echinocandins (caspofungin, anidulafungin and micafungin), polyenes (amphotericin B and nystatin) and 5-fluorocytosine (5-FC). The following mutation hot spots were identified: (1) ergosterol biosynthesis pathway mutations (ERG11 and UPC2), resulting in azole resistance; (2) overexpression of the efflux pumps, promoting azole resistance (transcription factor genes: tac1 and mrr1; transporter genes: CDR1, CDR2, MDR1, PDR16 and SNQ2); (3) cell wall biosynthesis mutations (FKS1, FKS2 and PDR1), conferring resistance to echinocandins; (4) mutations of nucleic acid synthesis/repair genes (FCY1, FCY2 and FUR1), resulting in 5-FC resistance; and (5) biofilm production, promoting general antifungal resistance. This review also provides a summary of standardized inhibitory breakpoints obtained from international guidelines for prominent Candida species. Notably, N. glabrata, P. kudriavzevii and C. auris demonstrate fluconazole resistance.
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Affiliation(s)
- Karolina M. Czajka
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (K.M.C.); (K.V.); (C.V.); (R.S.); (D.P.S.)
| | - Krishnan Venkataraman
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (K.M.C.); (K.V.); (C.V.); (R.S.); (D.P.S.)
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada;
| | | | - Stacey A. Santi
- Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada; (D.B.-K.); (S.A.S.)
| | - Chris Verschoor
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (K.M.C.); (K.V.); (C.V.); (R.S.); (D.P.S.)
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada;
- Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada; (D.B.-K.); (S.A.S.)
| | - Vasu D. Appanna
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada;
| | - Ravi Singh
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (K.M.C.); (K.V.); (C.V.); (R.S.); (D.P.S.)
- Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada; (D.B.-K.); (S.A.S.)
| | - Deborah P. Saunders
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (K.M.C.); (K.V.); (C.V.); (R.S.); (D.P.S.)
- Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada; (D.B.-K.); (S.A.S.)
| | - Sujeenthar Tharmalingam
- Medical Sciences Division, NOSM University, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada; (K.M.C.); (K.V.); (C.V.); (R.S.); (D.P.S.)
- School of Natural Sciences, Laurentian University, Sudbury, ON P3E 2C6, Canada;
- Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada; (D.B.-K.); (S.A.S.)
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Durand R, Jalbert-Ross J, Fijarczyk A, Dubé AK, Landry CR. Cross-feeding affects the target of resistance evolution to an antifungal drug. PLoS Genet 2023; 19:e1011002. [PMID: 37856537 PMCID: PMC10617708 DOI: 10.1371/journal.pgen.1011002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 10/31/2023] [Accepted: 10/02/2023] [Indexed: 10/21/2023] Open
Abstract
Pathogenic fungi are a cause of growing concern. Developing an efficient and safe antifungal is challenging because of the similar biological properties of fungal and host cells. Consequently, there is an urgent need to better understand the mechanisms underlying antifungal resistance to prolong the efficacy of current molecules. A major step in this direction would be to be able to predict or even prevent the acquisition of resistance. We leverage the power of experimental evolution to quantify the diversity of paths to resistance to the antifungal 5-fluorocytosine (5-FC), commercially known as flucytosine. We generated hundreds of independent 5-FC resistant mutants derived from two genetic backgrounds from wild isolates of Saccharomyces cerevisiae. Through automated pin-spotting, whole-genome and amplicon sequencing, we identified the most likely causes of resistance for most strains. Approximately a third of all resistant mutants evolved resistance through a pleiotropic drug response, a potentially novel mechanism in response to 5-FC, marked by cross-resistance to fluconazole. These cross-resistant mutants are characterized by a loss of respiration and a strong tradeoff in drug-free media. For the majority of the remaining two thirds, resistance was acquired through loss-of-function mutations in FUR1, which encodes an important enzyme in the metabolism of 5-FC. We describe conditions in which mutations affecting this particular step of the metabolic pathway are favored over known resistance mutations affecting a step upstream, such as the well-known target cytosine deaminase encoded by FCY1. This observation suggests that ecological interactions may dictate the identity of resistance hotspots.
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Affiliation(s)
- Romain Durand
- Département de Biochimie, de Microbiologie et de Bio-informatique, Faculté des Sciences et de Génie, Université Laval, Canada
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Canada
- PROTEO, Le regroupement québécois de recherche sur la fonction, l’ingénierie et les applications des protéines, Université Laval, Québec, Canada
- Centre de Recherche sur les Données Massives (CRDM), Université Laval, Québec, Canada
- Département de Biologie, Faculté des Sciences et de Génie, Université Laval, Québec, Canada
| | - Jordan Jalbert-Ross
- Département de Biochimie, de Microbiologie et de Bio-informatique, Faculté des Sciences et de Génie, Université Laval, Canada
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Canada
- PROTEO, Le regroupement québécois de recherche sur la fonction, l’ingénierie et les applications des protéines, Université Laval, Québec, Canada
- Centre de Recherche sur les Données Massives (CRDM), Université Laval, Québec, Canada
| | - Anna Fijarczyk
- Département de Biochimie, de Microbiologie et de Bio-informatique, Faculté des Sciences et de Génie, Université Laval, Canada
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Canada
- PROTEO, Le regroupement québécois de recherche sur la fonction, l’ingénierie et les applications des protéines, Université Laval, Québec, Canada
- Centre de Recherche sur les Données Massives (CRDM), Université Laval, Québec, Canada
- Département de Biologie, Faculté des Sciences et de Génie, Université Laval, Québec, Canada
| | - Alexandre K. Dubé
- Département de Biochimie, de Microbiologie et de Bio-informatique, Faculté des Sciences et de Génie, Université Laval, Canada
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Canada
- PROTEO, Le regroupement québécois de recherche sur la fonction, l’ingénierie et les applications des protéines, Université Laval, Québec, Canada
- Centre de Recherche sur les Données Massives (CRDM), Université Laval, Québec, Canada
- Département de Biologie, Faculté des Sciences et de Génie, Université Laval, Québec, Canada
| | - Christian R. Landry
- Département de Biochimie, de Microbiologie et de Bio-informatique, Faculté des Sciences et de Génie, Université Laval, Canada
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Canada
- PROTEO, Le regroupement québécois de recherche sur la fonction, l’ingénierie et les applications des protéines, Université Laval, Québec, Canada
- Centre de Recherche sur les Données Massives (CRDM), Université Laval, Québec, Canada
- Département de Biologie, Faculté des Sciences et de Génie, Université Laval, Québec, Canada
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Zhang J, Wang Z, Chen Y, Zhou Z, Yang Q, Fu Y, Zhao F, Li X, Chen Q, Fang L, Jiang Y, Yu Y. Antifungal susceptibility and molecular characteristics of Cryptococcus spp. based on whole-genome sequencing in Zhejiang Province, China. Front Microbiol 2022; 13:991703. [PMID: 36466641 PMCID: PMC9712201 DOI: 10.3389/fmicb.2022.991703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 10/31/2022] [Indexed: 06/05/2024] Open
Abstract
Cryptococcus spp. is a complex species that often causes cryptococcosis, which is one of the most common opportunistic infections in adults living with HIV and has very high morbidity and mortality rates. This study aimed to investigate the antifungal susceptibility profiles and epidemiological characteristics of the Cryptococcus neoformans species complex (CNSC) and the Cryptococcus gattii species complex (CGSC) in Zhejiang Province, China. A total of 177 CNSC and 3 CGSC isolates were collected, and antifungal susceptibility was tested by FUNGUS 3 and verified with an E-test. Moreover, multiple classification methods and genomic analyses were performed. The majority of the isolates (96.11%) were C. neoformans (formerly C. neoformans var. grubii) (ST5-VNI-A-α). Our study highlights that most of the patients with cryptococcosis were non-HIV patients in China, and nearly half of them did not have underlying diseases that led to immune insufficiency. Most of the Cryptococcus spp. isolates in this study were sensitive to common antifungal drugs. Two 5-flucytosine (5-FC)-resistant strains were identified, and FUR1 mutation was detected in the 5-FC-resistant isolates. Typing based on whole-genome sequencing (WGS) showed better discrimination than that achieved with multilocus sequence typing (MLST) and indicated a clear population structure. A phylogenetic analysis based on WGS included more genomic information than traditional classification methods.
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Affiliation(s)
- Junli Zhang
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
| | - Zhengan Wang
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
| | - Yan Chen
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
| | - Zhihui Zhou
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
| | - Qing Yang
- Department of Clinical Laboratory, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Ying Fu
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
- Department of Clinical Laboratory, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Feng Zhao
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
- Department of Clinical Laboratory, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Xi Li
- Department of Clinical Laboratory, Zhejiang Provincial People's Hospital, Hangzhou, China
| | - Qiong Chen
- Department of Clinical Laboratory, Affiliated Hangzhou First People’s Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Li Fang
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
| | - Yan Jiang
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
| | - Yunsong Yu
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, China
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Candida auris Pan-Drug-Resistant to Four Classes of Antifungal Agents. Antimicrob Agents Chemother 2022; 66:e0005322. [PMID: 35770999 PMCID: PMC9295560 DOI: 10.1128/aac.00053-22] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Candida auris is an urgent antimicrobial resistance threat due to its global emergence, high mortality, and persistent transmissions. Nearly half of C. auris clinical and surveillance cases in the United States are from the New York and New Jersey Metropolitan area. We performed genome, and drug-resistance analysis of C. auris isolates from a patient who underwent multi-visceral transplantation. Whole-genome comparisons of 19 isolates, collected over 72 days, revealed closed similarity (Average Nucleotide Identity > 0.9996; Aligned Percentage > 0.9764) and a distinct subcluster of NY C. auris South Asia Clade I. All isolates had azole-linked resistance in ERG11(K143R) and CDR1(V704L). Echinocandin resistance first appeared with FKS1(S639Y) mutation and then a unique FKS1(F635C) mutation. Flucytosine-resistant isolates had mutations in FCY1, FUR1, and ADE17. Two pan-drug-resistant C. auris isolates had uracil phosphoribosyltransferase deletion (FUR1[1Δ33]) and the elimination of FUR1 expression, confirmed by a qPCR test developed in this study. Besides ERG11 mutations, four amphotericin B-resistant isolates showed no distinct nonsynonymous variants suggesting unknown genetic elements driving the resistance. Pan-drug-resistant C. auris isolates were not susceptible to two-drug antifungal combinations tested by checkerboard, Etest, and time-kill methods. The fungal population pattern, discerned from SNP phylogenetic analysis, was consistent with in-hospital or inpatient evolution of C. auris isolates circulating locally and not indicative of a recent introduction from elsewhere. The emergence of pan-drug-resistance to four major classes of antifungals in C. auris is alarming. Patients at high risk for drug-resistant C. auris might require novel therapeutic strategies and targeted pre-and/or posttransplant surveillance.
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Delma FZ, Al-Hatmi AMS, Brüggemann RJM, Melchers WJG, de Hoog S, Verweij PE, Buil JB. Molecular Mechanisms of 5-Fluorocytosine Resistance in Yeasts and Filamentous Fungi. J Fungi (Basel) 2021; 7:jof7110909. [PMID: 34829198 PMCID: PMC8623157 DOI: 10.3390/jof7110909] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 10/19/2021] [Accepted: 10/23/2021] [Indexed: 12/30/2022] Open
Abstract
Effective management and treatment of fungal diseases is hampered by poor diagnosis, limited options for antifungal therapy, and the emergence of antifungal drug resistance. An understanding of molecular mechanisms contributing to resistance is essential to optimize the efficacy of currently available antifungals. In this perspective, one of the oldest antifungals, 5-fluorocytosine (5-FC), has been the focus of recent studies applying advanced genomic and transcriptomic techniques to decipher the order of events at the molecular level that lead to resistance. These studies have highlighted the complexity of resistance and provided new insights that are reviewed in the present paper.
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Affiliation(s)
- Fatima Zohra Delma
- Department of Medical Microbiology, Radboud University Medical Centre, 6252 AG Nijmegen, The Netherlands; (F.Z.D.); (W.J.G.M.); (P.E.V.)
| | - Abdullah M. S. Al-Hatmi
- Natural & Medical Sciences Research Center, University of Nizwa, Nizwa 616, Oman;
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
- Foundation Atlas of Clinical Fungi, 1214 GP Hilversum, The Netherlands
| | - Roger J. M. Brüggemann
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
- Department of Pharmacy, Radboud University Medical Center, 6252 AG Nijmegen, The Netherlands
| | - Willem J. G. Melchers
- Department of Medical Microbiology, Radboud University Medical Centre, 6252 AG Nijmegen, The Netherlands; (F.Z.D.); (W.J.G.M.); (P.E.V.)
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
| | - Sybren de Hoog
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
- Foundation Atlas of Clinical Fungi, 1214 GP Hilversum, The Netherlands
| | - Paul E. Verweij
- Department of Medical Microbiology, Radboud University Medical Centre, 6252 AG Nijmegen, The Netherlands; (F.Z.D.); (W.J.G.M.); (P.E.V.)
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
| | - Jochem B. Buil
- Department of Medical Microbiology, Radboud University Medical Centre, 6252 AG Nijmegen, The Netherlands; (F.Z.D.); (W.J.G.M.); (P.E.V.)
- Centre of Expertise in Mycology Radboudumc/CWZ, Radboudumc Center for Infectious Diseases (RCI), 6252 AG Nijmegen, The Netherlands; (R.J.M.B.); (S.d.H.)
- Correspondence: ; Tel.: +31-24-361-4356
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Striking Back against Fungal Infections: The Utilization of Nanosystems for Antifungal Strategies. Int J Mol Sci 2021; 22:ijms221810104. [PMID: 34576268 PMCID: PMC8466259 DOI: 10.3390/ijms221810104] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/13/2021] [Accepted: 09/15/2021] [Indexed: 12/19/2022] Open
Abstract
Fungal infections have become a major health concern, given that invasive infections by Candida, Cryptococcus, and Aspergillus species have led to millions of mortalities. Conventional antifungal drugs including polyenes, echinocandins, azoles, allylamins, and antimetabolites have been used for decades, but their limitations include off-target toxicity, drug-resistance, poor water solubility, low bioavailability, and weak tissue penetration, which cannot be ignored. These drawbacks have led to the emergence of novel antifungal therapies. In this review, we discuss the nanosystems that are currently utilized for drug delivery and the application of antifungal therapies.
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Galocha M, Costa IV, Teixeira MC. Carrier-Mediated Drug Uptake in Fungal Pathogens. Genes (Basel) 2020; 11:genes11111324. [PMID: 33182427 PMCID: PMC7697741 DOI: 10.3390/genes11111324] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 11/03/2020] [Accepted: 11/07/2020] [Indexed: 12/22/2022] Open
Abstract
Candida, Aspergillus, and Cryptococcus species are the most frequent cause of severe human fungal infections. Clinically relevant antifungal drugs are scarce, and their effectiveness are hampered by the ability of fungal cells to develop drug resistance mechanisms. Drug effectiveness and drug resistance in human pathogens is very often affected by their “transportome”. Many studies have covered a panoply of drug resistance mechanisms that depend on drug efflux pumps belonging to the ATP-Binding Cassette and Major Facilitator Superfamily. However, the study of drug uptake mechanisms has been, to some extent, overlooked in pathogenic fungi. This review focuses on discussing current knowledge on drug uptake systems in fungal pathogens, highlighting the need for further studies on this topic of great importance. The following subjects are covered: (i) drugs imported by known transporter(s) in pathogenic fungi; and (ii) drugs imported by known transporter(s) in the model yeast Saccharomyces cerevisiae or in human parasites, aimed at the identification of their homologs in pathogenic fungi. Besides its contribution to increase the understanding of drug-pathogen interactions, the practical implications of identifying drug importers in human pathogens are discussed, particularly focusing on drug development strategies.
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Affiliation(s)
- Mónica Galocha
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (M.G.); (I.V.C.)
- Biological Sciences Research Group, iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Inês Vieira Costa
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (M.G.); (I.V.C.)
- Biological Sciences Research Group, iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Miguel Cacho Teixeira
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; (M.G.); (I.V.C.)
- Biological Sciences Research Group, iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
- Correspondence: ; Tel.: +351-21-841-7772; Fax: +351-21-841-9199
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Billmyre RB, Applen Clancey S, Li LX, Doering TL, Heitman J. 5-fluorocytosine resistance is associated with hypermutation and alterations in capsule biosynthesis in Cryptococcus. Nat Commun 2020; 11:127. [PMID: 31913284 PMCID: PMC6949227 DOI: 10.1038/s41467-019-13890-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/29/2019] [Indexed: 12/27/2022] Open
Abstract
Patients infected with the fungal pathogen Cryptococcus are most effectively treated with a combination of 5-fluorocytosine (5FC) and amphotericin B. 5FC acts as a prodrug, which is converted into toxic 5-fluorouracil (5FU) upon uptake into fungal cells. However, the pathogen frequently develops resistance through unclear mechanisms. Here we show that resistance to 5FC in Cryptococcus deuterogattii is acquired more frequently in isolates with defects in DNA mismatch repair that confer an elevated mutation rate. We use whole genome sequencing of 16 independent isolates to identify mutations associated with 5FC resistance in vitro. We find mutations in known resistance genes (FUR1 and FCY2) and in a gene UXS1, previously shown to encode an enzyme that converts UDP-glucuronic acid to UDP-xylose for capsule biosynthesis, but not known to play a role in 5FC metabolism. Mutations in UXS1 lead to accumulation of UDP-glucuronic acid and alterations in nucleotide metabolism, which appear to suppress toxicity of both 5FC and its toxic derivative 5FU. The authors show that resistance to the antifungal 5-fluorocytosine in Cryptococcus deuterogattii is acquired more frequently in isolates with elevated mutation rate, and is associated with alterations in capsule biosynthesis and nucleotide metabolism.
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Affiliation(s)
- R Blake Billmyre
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA.,Stowers Institute for Medical Research, 1000 E 50th St., Kansas City, MO, 64110, USA
| | - Shelly Applen Clancey
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | - Lucy X Li
- Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Tamara L Doering
- Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA.
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Abstract
Antifungal resistance is an inevitable phenomenon when fungal pathogens are exposed to antifungal drugs. These drugs can be grouped in four distinct classes (azoles, candins, polyenes, and pyrimidine analogs) and are used in different clinical settings. Failures in therapy implicate the sequential or combined use of these different drug classes, which can result in some cases in the development of multidrug resistance (MDR). MDR is particularly challenging in the clinic since it drastically reduces possible treatment alternatives. In this study, we report the rapid development of MDR in Candida lusitaniae in a patient, which became resistant to all known antifungal agents used until now in medicine. To understand how MDR developed in C. lusitaniae, whole-genome sequencing followed by comparative genome analysis was undertaken in sequential MDR isolates. This helped to detect all specific mutations linked to drug resistance and explained the different MDR patterns exhibited by the clinical isolates. Multidrug resistance (MDR) has emerged in hospitals due to the use of several agents administered in combination or sequentially to the same individual. We reported earlier MDR in Candida lusitaniae during therapy with amphotericin B (AmB), azoles, and candins. Here, we used comparative genomic approaches between the initial susceptible isolate and 4 other isolates with different MDR profiles. From a total of 18 nonsynonymous single nucleotide polymorphisms (NSS) in genome comparisons with the initial isolate, six could be associated with MDR. One of the single nucleotide polymorphisms (SNPs) occurred in a putative transcriptional activator (MRR1) resulting in a V668G substitution in isolates resistant to azoles and 5-fluorocytosine (5-FC). We demonstrated by genome editing that MRR1 acted by upregulation of MFS7 (a multidrug transporter) in the presence of the V668G substitution. MFS7 itself mediated not only azole resistance but also 5-FC resistance, which represents a novel resistance mechanism for this drug class. Three other distinct NSS occurred in FKS1 (a glucan synthase gene that is targeted by candins) in three candin-resistant isolates. Last, two other NSS in ERG3 and ERG4 (ergosterol biosynthesis) resulting in nonsense mutations were revealed in AmB-resistant isolates, one of which accumulated the two ERG NSS. AmB-resistant isolates lacked ergosterol and exhibited sterol profiles, consistent with ERG3 and ERG4 defects. In conclusion, this genome analysis combined with genetics and metabolomics helped decipher the resistance profiles identified in this clinical case. MDR isolates accumulated six different mutations conferring resistance to all antifungal agents used in medicine. This case study illustrates the capacity of C. lusitaniae to rapidly adapt under drug pressure within the host.
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11
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Hashemi SE, Shokohi T, Abastabar M, Aslani N, Ghadamzadeh M, Haghani I. Species distribution and susceptibility profiles of Candida species isolated from vulvovaginal candidiasis, emergence of C. lusitaniae. Curr Med Mycol 2019; 5:26-34. [PMID: 32104741 PMCID: PMC7034787 DOI: 10.18502/cmm.5.4.2062] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Background and Purpose: The aim of the current study was to investigate the epidemiology of vulvovaginal candidiasis (VVC) and recurrent VVC (RVVC), as well as the antifungal susceptibility patterns of Candida species isolates. Materials and Methods: A cross-sectional study was carried out on 260 women suspected of VVC from February 2017 to January 2018. In order to identify Candida species isolated from the genital tracts, the isolates were subjected to polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) using enzymes Msp I and sequencing. Moreover, antifungal susceptibility testing was performed according to the Clinical and Laboratory Standards Institute guidelines (M27-A3). Results: Out of 250 subjects, 75 (28.8%) patients were affected by VVC, out of whom 15 (20%) cases had RVVC. Among the Candida species, C. albicans was the most common species (42/95; 44.21%), followed by C. lusitaniae (18/95; 18.95%), C. parapsilosis (13/95; 13.69%), C. glabrata (8/95; 8.42%), C. kefyr (6/95; 6.31%), C. famata (5/95; 5.26%), C. africana (2/95; 2.11%), and C. orthopsilosis (1/95; 1.05%), respectively. Multiple Candida species were observed in 28% (21/75) of the patients. Nystatin showed the narrowest range of minimum inhibitory concentration (MIC) (0.25-16 μg/ml) against all Candida strains, whereas fluconazole (0.063-64 μg/ml) demonstrated the widest MIC range. In the current study, C. lusitaniae, as the second most common causative agent of VVC, was susceptible to all antifungal agents. Furthermore, 61.1% of C. lusitaniae isolates were inhibited at a concentration of ≤ 2 μg/ml, while 38.9% (n=7) of them exhibited fluconazole MICs above the epidemiologic cutoff values (ECV). Candida species showed the highest overall resistance against fluconazole (61.3%), followed by itraconazole (45.2%) and caspofungin (23.7%). All of C. albicans strains were resistant to itraconazole with a MIC value of ≥ 1 μg/ml; in addition, 87.5% of them were resistant to fluconazole. Moreover, 100% and 87.5% of C. glabrata strains were resistant to caspofungin and fluconazole, respectively. Conclusion: As the findings revealed, the majority of VVC cases were caused by non-albicans Candida species which were often more resistant to antifungal agents. Candida lusitaniae generally had fluconazole MICs above the ECV. Given the propensity of C. lusitaniae to develop resistance under drug pressure, antifungals should be administered with caution. The emergence of these species justify the epidemiological surveillance surveys to watch out the distribution of yeast species.
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Affiliation(s)
- Seyed Ebrahim Hashemi
- Student Research Committee, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
| | - Tahereh Shokohi
- Invasive Fungi Research Centre (IFRC), Mazandaran University of Medical Sciences, Sari, Iran.,Department of Medical Mycology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
| | - Mahdi Abastabar
- Invasive Fungi Research Centre (IFRC), Mazandaran University of Medical Sciences, Sari, Iran.,Department of Medical Mycology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
| | - Narges Aslani
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mahbobeh Ghadamzadeh
- Gynecology and Obstetrics Department of Hazrat-e- Zainab Hospital, Babolsar, Iran
| | - Iman Haghani
- Department of Medical Mycology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
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12
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Vu K, Thompson GR, Roe CC, Sykes JE, Dreibe EM, Lockhart SR, Meyer W, Engelthaler DM, Gelli A. Flucytosine resistance in Cryptococcus gattii is indirectly mediated by the FCY2-FCY1-FUR1 pathway. Med Mycol 2018; 56:857-867. [PMID: 29554336 PMCID: PMC10905989 DOI: 10.1093/mmy/myx135] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 10/12/2017] [Indexed: 11/14/2022] Open
Abstract
Cryptococcosis is an opportunistic fungal infection caused by members of the two sibling species complexes: Cryptococcus neoformans and Cryptococcus gattii. Flucytosine (5FC) is one of the most widely used antifungals against Cryptococcus spp., yet very few studies have looked at the molecular mechanisms responsible for 5FC resistance in this pathogen. In this study, we examined 11 C. gattii clinical isolates of the major molecular type VGIII based on differential 5FC susceptibility and asked whether there were genomic changes in the key genes involved in flucytosine metabolism. Susceptibility assays and sequencing analysis revealed an association between a point mutation in the cytosine deaminase gene (FCY1) and 5FC resistance in two of the studied 5FC resistant C. gattii VGIII clinical isolates, B9322 and JS5. This mutation results in the replacement of arginine for histidine at position 29 and occurs within a variable stretch of amino acids. Heterologous expression of FCY1 and spot sensitivity assays, however, demonstrated that this point mutation did not have any effect on FCY1 activities and was not responsible for 5FC resistance. Comparative sequence analysis further showed that no changes in the amino acid sequence and no genomic alterations were observed within 1 kb of the upstream and downstream sequences of either cytosine permeases (FCY2-4) or uracil phosphoribosyltransferase (FUR1) genes in 5FC resistant and 5FC susceptible C. gattii VGIII isolates. The herein obtained results suggest that the observed 5FC resistance in the isolates B9322 and JS5 is due to changes in unknown protein(s) or pathway(s) that regulate flucytosine metabolism.
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Affiliation(s)
- Kiem Vu
- Department of Pharmacology, University of California, Davis, California, USA
| | - George R Thompson
- Department of Medical Microbiology and Immunology, University of California, Davis, California, USA
- Department of Internal Medicine, Division of Infectious Diseases, University of California Davis Medical Center, Davis, California, USA
| | - Chandler C Roe
- Translational Genomics Research Institute, Flagstaff, Arizona, USA
| | - Jane E Sykes
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | | | - Shawn R Lockhart
- Mycotic Diseases Branch, Centers for Disease Control and Prevention, Atlanta, Georgia USA
| | - Wieland Meyer
- Molecular Mycology Research Laboratory, Center for Infectious Diseases and Microbiology, Marie Bashir Institute for Emerging Infectious Diseases and Biosecurity, Westmead Clinical School, Sydney Medical School, Westmead Hospital, The University of Sydney, Westmead Institute for Medical Research, Sydney, Australia
| | | | - Angie Gelli
- Department of Pharmacology, University of California, Davis, California, USA
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13
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Mechanistic Basis of pH-Dependent 5-Flucytosine Resistance in Aspergillus fumigatus. Antimicrob Agents Chemother 2018; 62:AAC.02593-17. [PMID: 29610197 DOI: 10.1128/aac.02593-17] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 03/16/2018] [Indexed: 12/21/2022] Open
Abstract
The antifungal drug 5-flucytosine (5FC), a derivative of the nucleobase cytosine, is licensed for the treatment of fungal diseases; however, it is rarely used as a monotherapeutic to treat Aspergillus infection. Despite being potent against other fungal pathogens, 5FC has limited activity against Aspergillus fumigatus when standard in vitro assays are used to determine susceptibility. However, in modified in vitro assays where the pH is set to pH 5, the activity of 5FC increases significantly. Here we provide evidence that fcyB, a gene that encodes a purine-cytosine permease orthologous to known 5FC importers, is downregulated at pH 7 and is the primary factor responsible for the low efficacy of 5FC at pH 7. We also uncover two transcriptional regulators that are responsible for the repression of fcyB and, consequently, mediators of 5FC resistance, the CCAAT binding complex (CBC) and the pH regulatory protein PacC. We propose that the activity of 5FC might be enhanced by the perturbation of factors that repress fcyB expression, such as PacC or other components of the pH-sensing machinery.
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14
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Morio F, Jensen RH, Le Pape P, Arendrup MC. Molecular basis of antifungal drug resistance in yeasts. Int J Antimicrob Agents 2017; 50:599-606. [DOI: 10.1016/j.ijantimicag.2017.05.012] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 05/04/2017] [Accepted: 05/06/2017] [Indexed: 01/05/2023]
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15
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Biswas C, Chen SCA, Halliday C, Kennedy K, Playford EG, Marriott DJ, Slavin MA, Sorrell TC, Sintchenko V. Identification of genetic markers of resistance to echinocandins, azoles and 5-fluorocytosine in Candida glabrata by next-generation sequencing: a feasibility study. Clin Microbiol Infect 2017; 23:676.e7-676.e10. [PMID: 28344162 DOI: 10.1016/j.cmi.2017.03.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 03/03/2017] [Accepted: 03/18/2017] [Indexed: 01/05/2023]
Abstract
OBJECTIVES Multi-antifungal drug resistance in Candida glabrata is increasing. We examined the feasibility of next-generation sequencing (NGS) to investigate the presence of antifungal drug resistance markers in C. glabrata. METHODS The antifungal susceptibility of 12 clinical isolates and one ATCC strain of C. glabrata was determined using the Sensititre YeastOne® YO10 assay. These included three isolate pairs where the second isolate of each pair had developed a rise in drug MICs. Single nucleotide polymorphisms (SNPs) in genes known to be linked to echinocandin, azole and 5-fluorocytosine resistance were analysed in all isolates through NGS. RESULTS High-quality non-synonymous SNPs in antifungal resistance genes such as FKS1, FKS2, CgCDR1, CgPDR1 and FCY2 were identified. For two of three isolate pairs, there was a >60-fold rise in MICs to all echinocandins in the second isolate from each pair; one echinocandin-resistant isolate harboured a mutation in FKS1 (S629P) and the other in FKS2 (S663P). Of the third pair, both the 5-fluorocytosine-susceptible, and resistant isolates had a mutation in FCY2 (A237T). SNPs in CgPDR1 were found in pan-azole-resistant isolates. SNPs in other genes linked to azole resistance (CgCDR1, ERG9 and CgFLR1) were present in both azole-susceptible and azole-resistant isolates. SNPs were also identified in Candida adhesin genes EPA1, EPA6, PWP2 and PWP5 but their presence was not associated with higher drug MICs. CONCLUSIONS Genome-wide analysis of antifungal resistance markers was feasible and simultaneously revealed mutation patterns of genes implicated in resistance to different antifungal drug classes.
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Affiliation(s)
- C Biswas
- Centre for Infectious Diseases and Microbiology Laboratory Services, Westmead Hospital, Sydney, Australia; Centre for Infectious Diseases and Microbiology-Public Health, Westmead Hospital, Sydney, Australia.
| | - S C-A Chen
- Centre for Infectious Diseases and Microbiology Laboratory Services, Westmead Hospital, Sydney, Australia; Centre for Infectious Diseases and Microbiology-Public Health, Westmead Hospital, Sydney, Australia; Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Sydney, Australia
| | - C Halliday
- Centre for Infectious Diseases and Microbiology Laboratory Services, Westmead Hospital, Sydney, Australia
| | - K Kennedy
- Department of Infectious Diseases and Microbiology, Canberra Hospital, Australian National University Medical School, Canberra, Australia
| | - E G Playford
- Infection Management Services, Princess Alexandra Hospital, Brisbane, Australia
| | - D J Marriott
- Department of Microbiology and Infectious Diseases, St Vincent's Hospital, Sydney, Australia
| | - M A Slavin
- Department of Infectious Diseases, Peter MacCallum Cancer Centre, Melbourne, Australia
| | - T C Sorrell
- Centre for Infectious Diseases and Microbiology-Public Health, Westmead Hospital, Sydney, Australia; Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Sydney, Australia
| | - V Sintchenko
- Centre for Infectious Diseases and Microbiology Laboratory Services, Westmead Hospital, Sydney, Australia; Centre for Infectious Diseases and Microbiology-Public Health, Westmead Hospital, Sydney, Australia; Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Sydney, Australia
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16
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Acquired Multidrug Antifungal Resistance in Candida lusitaniae during Therapy. Antimicrob Agents Chemother 2015; 59:7715-22. [PMID: 26438490 DOI: 10.1128/aac.02204-15] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 09/26/2015] [Indexed: 12/20/2022] Open
Abstract
Candida lusitaniae is usually susceptible to echinocandins. Beta-1,3-glucan synthase encoded by FKS genes is the target of echinocandins. A few missense mutations in the C. lusitaniae FKS1 hot spot 1 (HS1) have been reported. We report here the rapid emergence of antifungal resistance in C. lusitaniae isolated during therapy with amphotericin B (AMB), caspofungin (CAS), and azoles for treatment of persistent candidemia in an immunocompromised child with severe enterocolitis and visceral adenoviral disease. As documented from restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis, the five C. lusitaniae isolates examined were related to each other. From antifungal susceptibility and molecular analyses, 5 different profiles (P) were obtained. These profiles included the following: profile 1 (P1) (CAS MIC [μg/ml], 0.5; fluconazole [FLC] MIC, 0.25), determined while the patient was being treated with liposomal AMB for 3 months; P2 (FLC MIC [μg/ml], 0.25; CAS MIC, 4), while the patient was being treated with CAS for 2 weeks; P3 (CAS MIC [μg/ml], 0.5; FLC MIC, 32), while the patient was being treated with azoles and CAS initially followed by azoles alone for a week; P4 (CAS MIC [μg/ml], 8; FLC MIC, 8), while the patient was being treated with both drugs for 3 weeks; and P5 (AMB MIC [μg/ml], 0.125; CAS MIC, 8), while the patient was being treated with AMB and FLC for 2 weeks. CAS resistance was associated with resistance not only to micafungin and anidulafungin but also to AMB. Analysis of CAS resistance revealed 3 novel FKS1 mutations in CAS-resistant isolates (S638Y in P2; S631Y in P4; S638P in P5). While S638Y and -P are within HS1, S631Y is in close proximity to this domain but was confirmed to confer candin resistance using a site-directed mutagenesis approach. FLC resistance could be linked with overexpression of major facilitator gene 7 (MFS7) in C. lusitaniae P2 and P4 and was associated with resistance to 5-flurocytosine. This clinical report describes resistance of C. lusitaniae to all common antifungals. While candins or azole resistance followed monotherapy, multidrug antifungal resistance emerged during combined therapy.
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17
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Maubon D, Garnaud C, Calandra T, Sanglard D, Cornet M. Resistance of Candida spp. to antifungal drugs in the ICU: where are we now? Intensive Care Med 2014; 40:1241-55. [PMID: 25091787 DOI: 10.1007/s00134-014-3404-7] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 07/10/2014] [Indexed: 12/11/2022]
Abstract
Current increases in antifungal drug resistance in Candida spp. and clinical treatment failures are of concern, as invasive candidiasis is a significant cause of mortality in intensive care units (ICUs). This trend reflects the large and expanding use of newer broad-spectrum antifungal agents, such as triazoles and echinocandins. In this review, we firstly present an overview of the mechanisms of action of the drugs and of resistance in pathogenic yeasts, subsequently focusing on recent changes in the epidemiology of antifungal resistance in ICU. Then, we emphasize the clinical impacts of these current trends. The emergence of clinical treatment failures due to resistant isolates is described. We also consider the clinical usefulness of recent advances in the interpretation of antifungal susceptibility testing and in molecular detection of the mutations underlying acquired resistance. We pay particular attention to practical issues relating to ICU patient management, taking into account the growing threat of antifungal drug resistance.
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Affiliation(s)
- Danièle Maubon
- Parasitologie-Mycologie, Institut de Biologie et de Pathologie, CHU de Grenoble, Grenoble, France,
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18
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Deletion of the uracil permease gene confers cross-resistance to 5-fluorouracil and azoles in Candida lusitaniae and highlights antagonistic interaction between fluorinated nucleotides and fluconazole. Antimicrob Agents Chemother 2014; 58:4476-85. [PMID: 24867971 DOI: 10.1128/aac.00009-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We characterized two additional membrane transporters (Fur4p and Dal4p) of the nucleobase cation symporter 1 (NCS1) family involved in the uptake transport of pyrimidines and related molecules in the opportunistic pathogenic yeast Candida lusitaniae. Simple and multiple null mutants were constructed by gene deletion and genetic crosses. The function of each transporter was characterized by supplementation experiments, and the kinetic parameters of the uptake transport of uracil were measured using radiolabeled substrate. Fur4p specifically transports uracil and 5-fluorouracil. Dal4p is very close to Fur4p and transports allantoin (glyoxyldiureide). Deletion of the FUR4 gene confers resistance to 5-fluorouracil as well as cross-resistance to triazoles and imidazole antifungals when they are used simultaneously with 5-fluorouracil. However, the nucleobase transporters are not involved in azole uptake. Only fluorinated pyrimidines, not pyrimidines themselves, are able to promote cross-resistance to azoles by both the salvage and the de novo pathway of pyrimidine synthesis. A reinterpretation of the data previously obtained led us to show that subinhibitory doses of 5-fluorocytosine, 5-fluorouracil, and 5-fluorouridine also were able to trigger resistance to fluconazole in susceptible wild-type strains of C. lusitaniae and of different Candida species. Our results suggest that intracellular fluorinated nucleotides play a key role in azole resistance, either by preventing azoles from targeting the lanosterol 14-alpha-demethylase or its catalytic site or by acting as a molecular switch for the triggering of efflux transport.
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Abstract
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. Cryptococcus neoformans, an environmental, opportunistic yeast, is annually responsible for an estimated million cases of meningitis and over 600,000 deaths, mostly among HIV-infected patients in sub-Saharan Africa and Asia. Using RNA-seq, we analyzed the gene expression of two strains of C. neoformans obtained from the cerebrospinal fluid (CSF) of infected patients, thus creating a comprehensive snapshot of the yeasts’ genetic responses within the human body. By comparing the gene expression of each clinical strain under three conditions (in vivo CSF, ex vivo CSF, and laboratory culture), we identified genes and pathways that were uniquely regulated by exposure to CSF and likely crucial for the survival of C. neoformans in the central nervous system. Further analyses revealed genetic diversity between the strains, providing evidence for cryptococcal evolution and strain specificity. This ability to characterize transcription in vivo enables the elucidation of specific genetic responses that promote disease production and progression.
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Montibus M, Ducos C, Bonnin-Verdal MN, Bormann J, Ponts N, Richard-Forget F, Barreau C. The bZIP transcription factor Fgap1 mediates oxidative stress response and trichothecene biosynthesis but not virulence in Fusarium graminearum. PLoS One 2013; 8:e83377. [PMID: 24349499 PMCID: PMC3861502 DOI: 10.1371/journal.pone.0083377] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 11/01/2013] [Indexed: 11/22/2022] Open
Abstract
Redox sensing is of primary importance for fungi to cope with oxidant compounds found in their environment. Plant pathogens are particularly subject to the oxidative burst during the primary steps of infection. In the budding yeast Saccharomyces cerevisiae, it is the transcription factor Yap1 that mediates the response to oxidative stress via activation of genes coding for detoxification enzymes. In the cereal pathogen Fusarium graminearum, Fgap1 a homologue of Yap1 was identified and its role was investigated. During infection, this pathogen produces mycotoxins belonging to the trichothecenes family that accumulate in the grains. The global regulation of toxin biosynthesis is not completely understood. However, it is now clearly established that an oxidative stress activates the production of toxins by F. graminearum. The involvement of Fgap1 in this activation was investigated. A deleted mutant and a strain expressing a truncated constitutive form of Fgap1 were constructed. None of the mutants was affected in pathogenicity. The deleted mutant showed higher level of trichothecenes production associated with overexpression of Tri genes. Moreover activation of toxin accumulation in response to oxidative stress was no longer observed. Regarding the mutant with the truncated constitutive form of Fgap1, toxin production was strongly reduced. Expression of oxidative stress response genes was not activated in the deleted mutant and expression of the gene encoding the mitochondrial superoxide dismutase MnSOD1 was up-regulated in the mutant with the truncated constitutive form of Fgap1. Our results demonstrate that Fgap1 plays a key role in the link between oxidative stress response and F. graminearum secondary metabolism.
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Affiliation(s)
- Mathilde Montibus
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
- * E-mail:
| | - Christine Ducos
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
| | | | - Jorg Bormann
- University of Hamburg, Biocenter Klein Flottbek, Department of Molecular Phytopathology and Genetics, Hamburg, Germany
| | - Nadia Ponts
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
| | - Florence Richard-Forget
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
| | - Christian Barreau
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
- Centre National de la Recherche Scientifique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
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Kabir MA, Ahmad Z. Candida infections and their prevention. ISRN PREVENTIVE MEDICINE 2012; 2013:763628. [PMID: 24977092 PMCID: PMC4062852 DOI: 10.5402/2013/763628] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 10/04/2012] [Indexed: 12/15/2022]
Abstract
Infections caused by Candida species have been increased dramatically worldwide due to the increase in immunocompromised patients. For the prevention and cure of candidiasis, several strategies have been adopted at clinical level. Candida infected patients are commonly treated with a variety of antifungal drugs such as fluconazole, amphotericin B, nystatin, and flucytosine. Moreover, early detection and speciation of the fungal agents will play a crucial role for administering appropriate drugs for antifungal therapy. Many modern technologies like MALDI-TOF-MS, real-time PCR, and DNA microarray are being applied for accurate and fast detection of the strains. However, during prolonged use of these drugs, many fungal pathogens become resistant and antifungal therapy suffers. In this regard, combination of two or more antifungal drugs is thought to be an alternative to counter the rising drug resistance. Also, many inhibitors of efflux pumps have been designed and tested in different models to effectively treat candidiasis. However, most of the synthetic drugs have side effects and biomedicines like antibodies and polysaccharide-peptide conjugates could be better alternatives and safe options to prevent and cure the diseases. Furthermore, availability of genome sequences of Candida
albicans and other non-albicans strains has made it feasible to analyze the genes for their roles in adherence, penetration, and establishment of diseases. Understanding the biology of Candida species by applying different modern and advanced technology will definitely help us in preventing and curing the diseases caused by fungal pathogens.
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Affiliation(s)
- M Anaul Kabir
- Molecular Genetics Laboratory, School of Biotechnology, National Institute of Technology Calicut, Calicut 673601, India
| | - Zulfiqar Ahmad
- Department of Biological and Environmental Sciences, Alabama A&M University, Normal, AL 35762, USA
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Kabir MA, Hussain MA, Ahmad Z. Candida albicans: A Model Organism for Studying Fungal Pathogens. ISRN MICROBIOLOGY 2012; 2012:538694. [PMID: 23762753 PMCID: PMC3671685 DOI: 10.5402/2012/538694] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Accepted: 08/30/2012] [Indexed: 01/12/2023]
Abstract
Candida albicans is an opportunistic human fungal pathogen that causes candidiasis. As healthcare has been improved worldwide, the number of immunocompromised patients has been increased to a greater extent and they are highly susceptible to various pathogenic microbes and C. albicans has been prominent among the fungal pathogens. The complete genome sequence of this pathogen is now available and has been extremely useful for the identification of repertoire of genes present in this pathogen. The major challenge is now to assign the functions to these genes of which 13% are specific to C. albicans. Due to its close relationship with yeast Saccharomyces cerevisiae, an edge over other fungal pathogens because most of the technologies can be directly transferred to C. albicans from S. cerevisiae and it is amenable to mutation, gene disruption, and transformation. The last two decades have witnessed enormous amount of research activities on this pathogen that leads to the understanding of host-parasite interaction, infections, and disease propagation. Clearly, C. albicans has emerged as a model organism for studying fungal pathogens along with other two fungi Aspergillus fumigatus and Cryptococcus neoformans. Understanding its complete life style of C. albicans will undoubtedly be useful for developing potential antifungal drugs and tackling Candida infections. This will also shed light on the functioning of other fungal pathogens.
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Affiliation(s)
- M Anaul Kabir
- Molecular Genetics Laboratory, School of Biotechnology, National Institute of Technology Calicut, Calicut 673601, Kerala, India
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Progress in antifungal susceptibility testing of Candida spp. by use of Clinical and Laboratory Standards Institute broth microdilution methods, 2010 to 2012. J Clin Microbiol 2012; 50:2846-56. [PMID: 22740712 DOI: 10.1128/jcm.00937-12] [Citation(s) in RCA: 353] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antifungal susceptibility testing of Candida has been standardized and refined and now may play a useful role in managing Candida infections. Important new developments include validation of 24-h reading times for all antifungal agents and the establishment of species-specific epidemiological cutoff values (ECVs) for the systemically active antifungal agents and both common and uncommon species of Candida. The clinical breakpoints (CBPs) for fluconazole, voriconazole, and the echinocandins have been revised to provide species-specific interpretive criteria for the six most common species. The revised CBPs not only are predictive of clinical outcome but also provide a more sensitive means of identifying those strains with acquired or mutational resistance mechanisms. This brief review serves as an update on the new developments in the antifungal susceptibility testing of Candida spp. using Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BMD) methods.
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Pfaller MA, Castanheira M, Jones RN. Advances in Antifungal Susceptibility Testing of Candida, 2010–2012. CURRENT FUNGAL INFECTION REPORTS 2012. [DOI: 10.1007/s12281-012-0092-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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A TRP5/5-fluoroanthranilic acid counter-selection system for gene disruption in Candida guilliermondii. Curr Genet 2012; 58:245-54. [DOI: 10.1007/s00294-012-0377-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 05/02/2012] [Accepted: 05/06/2012] [Indexed: 10/28/2022]
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Wild-type MIC distributions and epidemiological cutoff values for amphotericin B, flucytosine, and itraconazole and Candida spp. as determined by CLSI broth microdilution. J Clin Microbiol 2012; 50:2040-6. [PMID: 22461672 DOI: 10.1128/jcm.00248-12] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clinical breakpoints (CBPs) and epidemiological cutoff values (ECVs) have been established for several Candida spp. and the newer triazoles and echinocandins but are not yet available for older antifungal agents, such as amphotericin B, flucytosine, or itraconazole. We determined species-specific ECVs for amphotericin B (AMB), flucytosine (FC) and itraconazole (ITR) for eight Candida spp. (30,221 strains) using isolates from 16 different laboratories in Brazil, Canada, Europe, and the United States, all tested by the CLSI reference microdilution method. The calculated 24- and 48-h ECVs expressed in μg/ml (and the percentages of isolates that had MICs less than or equal to the ECV) for AMB, FC, and ITR, respectively, were 2 (99.8)/2 (99.2), 0.5 (94.2)/1 (91.4), and 0.12 (95.0)/0.12 (92.9) for C. albicans; 2 (99.6)/2 (98.7), 0.5 (98.0)/0.5 (97.5), and 2 (95.2)/4 (93.5) for C. glabrata; 2 (99.7)/2 (97.3), 0.5 (98.7)/0.5 (97.8), and 05. (99.7)/0.5 (98.5) for C. parapsilosis; 2 (99.8)/2 (99.2), 0.5 (93.0)/1 (90.5), and 0.5 (97.8)/0.5 (93.9) for C. tropicalis; 2 (99.3)/4 (100.0), 32 (99.4)/32 (99.3), and 1 (99.0)/2 (100.0) for C. krusei; 2 (100.0)/4 (100.0), 0.5 (95.3)/1 (92.9), and 0.5 (95.8)/0.5 (98.1) for C. lusitaniae; -/2 (100.0), 0.5 (98.8)/0.5 (97.7), and 0.25 (97.6)/0.25 (96.9) for C. dubliniensis; and 2 (100.0)/2 (100.0), 1 (92.7)/-, and 1 (100.0)/2 (100.0) for C. guilliermondii. In the absence of species-specific CBP values, these wild-type (WT) MIC distributions and ECVs will be useful for monitoring the emergence of reduced susceptibility to these well-established antifungal agents.
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Chen YN, Lo HJ, Wu CC, Ko HC, Chang TP, Yang YL. Loss of heterozygosity of FCY2 leading to the development of flucytosine resistance in Candida tropicalis. Antimicrob Agents Chemother 2011; 55:2506-14. [PMID: 21422221 PMCID: PMC3101439 DOI: 10.1128/aac.01777-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 01/28/2011] [Accepted: 03/03/2011] [Indexed: 11/20/2022] Open
Abstract
As fluconazole resistance becomes an emerging issue for treating infections caused by Candida tropicalis, searching for alternative becomes a prominent task. In the present study, 97 clinical isolates of C. tropicalis were tested for the susceptibilities to flucytosine (5FC) with the Etest method. Although only one isolate was resistant to 5FC, 30 susceptible isolates could produce resistant progeny after exposure to the drug. Interestingly, 22 of these 30 clinical isolates had a heterozygous G/T at the 145th position on FCY2, encoding purine-cytosine permease, whereas their progeny recovered from within the inhibitory ellipses had homozygous T/T, resulting in null alleles for both copies of the gene and produced only truncated proteins, effecting the 5FC resistance. Furthermore, we found that two major fluconazole-resistant clinical clones, diploid sequence type 98 (DST98) and DST140, had a homozygous G/G at the 145th position, and neither was able to produce 5FC-resistant progeny within the inhibitory ellipses. Hence, strains of C. tropicalis containing heterozygous alleles may develop 5FC resistance readily, whereas those with homozygous G/G wild-type alleles can be treated with 5FC. Subsequently, a combination of 5FC and another antifungal drug is applicable for treating infections of C. tropicalis.
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Affiliation(s)
- Yen-Ning Chen
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu
| | - Hsiu-Jung Lo
- Division of Infectious Diseases, National Health Research Institutes, Miaoli
| | - Chia-Chen Wu
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan
| | - Hui-Ching Ko
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan
| | - Te-Pin Chang
- Division of Infectious Diseases, National Health Research Institutes, Miaoli
| | - Yun-Liang Yang
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan
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Development of echinocandin resistance in Clavispora lusitaniae during caspofungin treatment. J Clin Microbiol 2011; 49:2304-6. [PMID: 21490186 DOI: 10.1128/jcm.00325-11] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clavispora lusitaniae is an opportunistic human pathogen responsible for 0.6 to 2% of candidemia. This species is intrinsically susceptible to echinocandins. Nevertheless, in this study, development of echinocandin resistance in C. lusitaniae isolates was observed during caspofungin treatment. This resistance resulted from missense mutation in the echinocandin target Fks1 gene.
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El-Kirat-Chatel S, Dementhon K, Noël T. A two-step cloning-free PCR-based method for the deletion of genes in the opportunistic pathogenic yeast Candida lusitaniae. Yeast 2011; 28:321-30. [PMID: 21456057 DOI: 10.1002/yea.1836] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 11/18/2010] [Indexed: 11/07/2022] Open
Abstract
We describe a new cloning-free strategy to delete genes in the opportunistic pathogenic yeast Candida lusitaniae. We first constructed two ura3 Δ strains in C. lusitaniae for their use in transformation experiments. One was deleted for the entire URA3 coding sequence; the other possessed a partial deletion within the coding region, which was used to determine the minimum amount of homology required for efficient homologous recombination by double crossing-over of a linear DNA fragment restoring URA3 expression. This amount was estimated to 200 bp on each side of the DNA fragment. These data constituted the basis of the development of a strategy to construct DNA cassettes for gene deletion by a cloning-free overlapping PCR method. Two cassettes were necessary in two successive transformation steps for the complete removal of a gene of interest. As an example, we report here the deletion of the LEU2 gene. The first cassette was constituted by the URA3 gene flanked by two large fragments (500 bp) homologous to the 5' and 3' non-coding regions of LEU2. After transformation of an ura3 Δ recipient strain and integration of the cassette at the LEU2 locus, the URA3 gene was removed by a second transformation round with a DNA cassette made by the fusion between the 5' and 3' non-coding regions of the LEU2 gene. The overall procedure takes less than 2 weeks and allows the creation of a clean null mutant that retains no foreign DNA sequence integrated in its genome.
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Affiliation(s)
- Sofiane El-Kirat-Chatel
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, University of Bordeaux 2, CNRS UMR5234, Bordeaux, France
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Coleman DC, Moran GP, McManus BA, Sullivan DJ. Mechanisms of antifungal drug resistance in Candida dubliniensis. Future Microbiol 2010; 5:935-49. [PMID: 20521937 DOI: 10.2217/fmb.10.51] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Candida dubliniensis was first described in 1995 and is the most closely related species to the predominant human fungal pathogen Candida albicans. C. dubliniensis is significantly less prevalent and less pathogenic than C. albicans and is primarily associated with infections in HIV-infected individuals and other immunocompromised cohorts. The population structure of C. dubliniensis consists of three well-defined major clades and is significantly less diverse than C. albicans. The majority of C. dubliniensis isolates are susceptible to antifungal drugs commonly used to treat Candida infections. To date only two major patterns of antifungal drug resistance have been identified and the molecular mechanisms of these are very similar to the resistance mechanisms that have been described previously in C. albicans. However, significant differences are evident in the predominant antifungal drug mechanisms employed by C. dubliniensis, differences that reflect its more clonal nature, its lower prevalence and characteristics of its genome, the complete sequence of which has only recently been determined.
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Affiliation(s)
- David C Coleman
- Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, University of Dublin, Trinity College Dublin, Dublin 2, Republic of Ireland.
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Mutational analysis of flucytosine resistance in Candida glabrata. Antimicrob Agents Chemother 2010; 54:4733-8. [PMID: 20823283 DOI: 10.1128/aac.00605-10] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The antifungal flucytosine (5-fluorocytosine [5FC]) is a prodrug metabolized to its toxic form, 5-fluorouracil (5FU), only by organisms expressing cytosine deaminase. One such organism is Candida glabrata, which has emerged as the second most common agent of bloodstream and mucosal candidiasis. This emergence has been attributed to the high rate at which C. glabrata develops resistance to azole antifungals. As an oral agent, 5FC represents an attractive alternative or complement to azoles; however, the frequency of 5FC resistance mutations and the mechanisms by which these mutations confer resistance have been explored only minimally. On RPMI 1640 medium containing 1 μg/ml 5FC (32-fold above the MIC, but less than 1/10 of typical serum levels), resistant mutants occurred at a relatively low frequency (2 × 10⁻⁷). Three of six mutants characterized were 5FU cross-resistant, suggesting a mutation downstream of the Fcy1 gene (cytosine deaminase), which was confirmed by sequence analysis of the Fur1 gene (uracil phosphoribosyl transferase). The remaining three mutants had Fcy1 mutations. To ascertain the effects of 5FC resistance mutations on enzyme function, mutants were isolated in ura3 strains. Three of seven mutants harbored Fcy1 mutations and failed to grow in uridine-free, cytosine-supplemented medium, consistent with inactive Fcy1. The remainder grew in this medium and had wild-type Fcy1; further analysis revealed these to be mutated in the Fcy2L homolog of S. cerevisiae Fcy2 (purine-cytosine transporter). Based on this analysis, we characterized three 5FC-resistant clinical isolates, and mutations were identified in Fur1 and Fcy1. These data provide a framework for understanding 5FC resistance in C. glabrata and potentially in other fungal pathogens.
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Morschhäuser J. Regulation of multidrug resistance in pathogenic fungi. Fungal Genet Biol 2010; 47:94-106. [DOI: 10.1016/j.fgb.2009.08.002] [Citation(s) in RCA: 215] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 07/21/2009] [Accepted: 08/02/2009] [Indexed: 12/21/2022]
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A Ser29Leu substitution in the cytosine deaminase Fca1p is responsible for clade-specific flucytosine resistance in Candida dubliniensis. Antimicrob Agents Chemother 2009; 53:4678-85. [PMID: 19704126 DOI: 10.1128/aac.00607-09] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The population structure of the opportunistic yeast pathogen Candida dubliniensis is composed of three main multilocus sequence typing clades (clades C1 to C3), and clade C3 predominantly consists of isolates from the Middle East that exhibit high-level resistance (MIC(50) > or = 128 microg/ml) to the fungicidal agent flucytosine (5FC). The close relative of C. dubliniensis, C. albicans, also exhibits clade-specific resistance to 5FC, and resistance is most commonly mediated by an Arg101Cys substitution in the FUR1 gene encoding uracil phosphoribosyltransferase. Broth microdilution assays with fluorouracil (5FU), the toxic deaminated form of 5FC, showed that both 5FC-resistant and 5FC-susceptible C. dubliniensis isolates exhibited similar 5FU MICs, suggesting that the C. dubliniensis cytosine deaminase (Fca1p) encoded by C. dubliniensis FCA1 (CdFCA1) may play a role in mediating C. dubliniensis clade-specific 5FC resistance. Amino acid sequence analysis of the CdFCA1 open reading frame (ORF) identified a homozygous Ser29Leu substitution in all 12 5FC-resistant isolates investigated which was not present in any of the 9 5FC-susceptible isolates examined. The tetracycline-inducible expression of the CdFCA1 ORF from a 5FC-susceptible C. dubliniensis isolate in two separate 5FC-resistant clade C3 isolates restored susceptibility to 5FC, demonstrating that the Ser29Leu substitution was responsible for the clade-specific 5FC resistance and that the 5FC resistance encoded by FCA1 genes with the Ser29Leu transition is recessive. Quantitative real-time PCR analysis showed no significant difference in CdFCA1 expression between 5FC-susceptible and 5FC-resistant isolates in either the presence or the absence of subinhibitory concentrations of 5FC, suggesting that the Ser29Leu substitution in the CdFCA1 ORF is the sole cause of 5FC resistance in clade C3 C. dubliniensis isolates.
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