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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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Takei S, Teramoto K, Fujimura J, Fujiwara M, Suzuki M, Fukui Y, Sekiguchi Y, Kawakami T, Chonan M, Wakita M, Horiuchi Y, Miida T, Naito T, Kirikae T, Tada T, Tabe Y. Isolation and identification of Wickerhamiella tropicalis from blood culture by MALDI-MS. Front Cell Infect Microbiol 2024; 14:1361432. [PMID: 38510957 PMCID: PMC10953818 DOI: 10.3389/fcimb.2024.1361432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Accepted: 02/20/2024] [Indexed: 03/22/2024] Open
Abstract
Wickerhamiella is a genus of budding yeast that is mainly isolated from environmental samples, and 40 species have been detected. The yeast isolated from human clinical samples usually only contain three species: W. infanticola, W. pararugosa and W. sorbophila. In this study, we isolated W. tropicalis from a blood sample of a six-year-old female with a history of B-cell precursor lymphoblastic leukemia in Japan in 2022. Though the strain was morphologically identified as Candida species by routine microbiological examinations, it was subsequently identified as W. tropicalis by sequencing the internal transcribed spacer (ITS) of ribosomal DNA (rDNA). The isolate had amino acid substitutions in ERG11 and FKS1 associated with azole and echinocandin resistance, respectively, in Candida species and showed intermediate-resistant to fluconazole and micafungin. The patient was successfully treated with micafungin. Furthermore, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) detected three novel peaks that are specific for W. tropicalis, indicating that MALDI-MS analysis is useful for rapid detection of Wickerhamiella species in routine microbiological examinations.
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Affiliation(s)
- Satomi Takei
- Department of Clinical Laboratory Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Department of MALDI-TOF MS Practical Application Research, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Kanae Teramoto
- Department of MALDI-TOF MS Practical Application Research, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Analytical & Measurement Instruments Division, Shimadzu Corporation, Kyoto, Japan
| | - Junya Fujimura
- Department of Pediatrics, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Megumi Fujiwara
- Department of Pediatrics, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Mai Suzuki
- Department of General Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yukiko Fukui
- Department of General Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yuji Sekiguchi
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
| | - Takaaki Kawakami
- Department of Clinical Laboratory, Juntendo University Hospital, Tokyo, Japan
| | - Masayoshi Chonan
- Department of Clinical Laboratory, Juntendo University Hospital, Tokyo, Japan
| | - Mitsuru Wakita
- Department of Clinical Laboratory, Juntendo University Hospital, Tokyo, Japan
| | - Yuki Horiuchi
- Department of Clinical Laboratory Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Takashi Miida
- Department of Clinical Laboratory Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Toshio Naito
- Department of MALDI-TOF MS Practical Application Research, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Department of General Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Teruo Kirikae
- Department of MALDI-TOF MS Practical Application Research, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Department of Microbiome Research, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Tatsuya Tada
- Department of Microbiology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yoko Tabe
- Department of Clinical Laboratory Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Department of MALDI-TOF MS Practical Application Research, Juntendo University Graduate School of Medicine, Tokyo, Japan
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Moreau J, Noël T, Point K, Tewes F, Deroche L, Clarhaut J, Fitton-Ouhabi V, Perraud E, Marchand S, Buyck JM, Brunet K. Pan-azole-resistant Meyerozyma guilliermondii clonal isolates harbouring a double F126L and L505F mutation in Erg11. Mycoses 2024; 67:e13704. [PMID: 38429226 DOI: 10.1111/myc.13704] [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: 11/16/2023] [Revised: 01/29/2024] [Accepted: 02/02/2024] [Indexed: 03/03/2024]
Abstract
BACKGROUND Meyerozyma guilliermondii is a yeast species responsible for invasive fungal infections. It has high minimum inhibitory concentrations (MICs) to echinocandins, the first-line treatment of candidemia. In this context, azole antifungal agents are frequently used. However, in recent years, a number of azole-resistant strains have been described. Their mechanisms of resistance are currently poorly studied. OBJECTIVE The aim of this study was consequently to understand the mechanisms of azole resistance in several clinical isolates of M. guilliermondii. METHODS Ten isolates of M. guilliermondii and the ATCC 6260 reference strain were studied. MICs of azoles were determined first. Whole genome sequencing of the isolates was then carried out and the mutations identified in ERG11 were expressed in a CTG clade yeast model (C. lusitaniae). RNA expression of ERG11, MDR1 and CDR1 was evaluated by quantitative PCR. A phylogenic analysis was developed and performed on M. guilliermondii isolates. Lastly, in vitro experiments on fitness cost and virulence were carried out. RESULTS Of the ten isolates tested, three showed pan-azole resistance. A combination of F126L and L505F mutations in Erg11 was highlighted in these three isolates. Interestingly, a combination of these two mutations was necessary to confer azole resistance. An overexpression of the Cdr1 efflux pump was also evidenced in one strain. Moreover, the three pan-azole-resistant isolates were shown to be genetically related and not associated with a fitness cost or a lower virulence, suggesting a possible clonal transmission. CONCLUSION In conclusion, this study identified an original combination of ERG11 mutations responsible for pan-azole-resistance in M. guilliermondii. Moreover, we proposed a new MLST analysis for M. guilliermondii that identified possible clonal transmission of pan-azole-resistant strains. Future studies are needed to investigate the distribution of this clone in hospital environment and should lead to the reconsideration of the treatment for this species.
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Affiliation(s)
- Jérémy Moreau
- Université de Poitiers, INSERM U1070 PHAR2, Poitiers, France
| | - Thierry Noël
- Université de Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Kévin Point
- Université de Poitiers, INSERM U1070 PHAR2, Poitiers, France
| | - Frédéric Tewes
- Université de Poitiers, INSERM U1070 PHAR2, Poitiers, France
| | - Luc Deroche
- CHU de Poitiers, Service de Virologie, Poitiers, France
| | - Jonathan Clarhaut
- Université de Poitiers, INSERM U1070 PHAR2, Poitiers, France
- CHU de Poitiers, Service de Toxicologie-Pharmacocinétique, Poitiers, France
| | - Valérie Fitton-Ouhabi
- Université de Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Estelle Perraud
- CHU de Poitiers, Service de Parasitologie et Mycologie Médicale, Poitiers, France
| | - Sandrine Marchand
- Université de Poitiers, INSERM U1070 PHAR2, Poitiers, France
- CHU de Poitiers, Service de Toxicologie-Pharmacocinétique, Poitiers, France
| | - Julien M Buyck
- Université de Poitiers, INSERM U1070 PHAR2, Poitiers, France
| | - Kévin Brunet
- Université de Poitiers, INSERM U1070 PHAR2, Poitiers, France
- CHU de Poitiers, Service de Parasitologie et Mycologie Médicale, Poitiers, France
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Tsybruk TV, Kaluzhskiy LA, Mezentsev YV, Makarieva TN, Tabakmaher KM, Ivanchina NV, Dmitrenok PS, Baranovsky AV, Gilep AA, Ivanov AS. Molecular Cloning, Heterologous Expression, Purification, and Evaluation of Protein-Ligand Interactions of CYP51 of Candida krusei Azole-Resistant Fungal Strain. Biomedicines 2023; 11:2873. [PMID: 38001874 PMCID: PMC10668980 DOI: 10.3390/biomedicines11112873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 10/17/2023] [Accepted: 10/19/2023] [Indexed: 11/26/2023] Open
Abstract
Due to the increasing prevalence of fungal diseases caused by fungi of the genus Candida and the development of pathogen resistance to available drugs, the need to find new effective antifungal agents has increased. Azole antifungals, which are inhibitors of sterol-14α-demethylase or CYP51, have been widely used in the treatment of fungal infections over the past two decades. Of special interest is the study of C. krusei CYP51, since this fungus exhibit resistance not only to azoles, but also to other antifungal drugs and there is no available information about the ligand-binding properties of CYP51 of this pathogen. We expressed recombinant C. krusei CYP51 in E. coli cells and obtained a highly purified protein. Application of the method of spectrophotometric titration allowed us to study the interaction of C. krusei CYP51 with various ligands. In the present work, the interaction of C. krusei CYP51 with azole inhibitors, and natural and synthesized steroid derivatives was evaluated. The obtained data indicate that the resistance of C. krusei to azoles is not due to the structural features of CYP51 of this microorganism, but rather to another mechanism. Promising ligands that demonstrated sufficiently strong binding in the micromolar range to C. krusei CYP51 were identified, including compounds 99 (Kd = 1.02 ± 0.14 µM) and Ch-4 (Kd = 6.95 ± 0.80 µM). The revealed structural features of the interaction of ligands with the active site of C. krusei CYP51 can be taken into account in the further development of new selective modulators of the activity of this enzyme.
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Affiliation(s)
- Tatsiana V. Tsybruk
- Institute of Bioorganic Chemistry NASB, 5 Building 2, V.F. Kuprevich Street, 220084 Minsk, Belarus; (A.V.B.); (A.A.G.)
| | - Leonid A. Kaluzhskiy
- Institute of Biomedical Chemistry, Pogodinskaya Str. 10 Building 8, 119121 Moscow, Russia; (L.A.K.); (Y.V.M.)
| | - Yuri V. Mezentsev
- Institute of Biomedical Chemistry, Pogodinskaya Str. 10 Building 8, 119121 Moscow, Russia; (L.A.K.); (Y.V.M.)
| | - Tatyana N. Makarieva
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Pr. 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (T.N.M.); (K.M.T.); (N.V.I.); (P.S.D.)
| | - Kseniya M. Tabakmaher
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Pr. 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (T.N.M.); (K.M.T.); (N.V.I.); (P.S.D.)
| | - Natalia V. Ivanchina
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Pr. 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (T.N.M.); (K.M.T.); (N.V.I.); (P.S.D.)
| | - Pavel S. Dmitrenok
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Pr. 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (T.N.M.); (K.M.T.); (N.V.I.); (P.S.D.)
| | - Alexander V. Baranovsky
- Institute of Bioorganic Chemistry NASB, 5 Building 2, V.F. Kuprevich Street, 220084 Minsk, Belarus; (A.V.B.); (A.A.G.)
| | - Andrei A. Gilep
- Institute of Bioorganic Chemistry NASB, 5 Building 2, V.F. Kuprevich Street, 220084 Minsk, Belarus; (A.V.B.); (A.A.G.)
- Institute of Biomedical Chemistry, Pogodinskaya Str. 10 Building 8, 119121 Moscow, Russia; (L.A.K.); (Y.V.M.)
| | - Alexis S. Ivanov
- Institute of Biomedical Chemistry, Pogodinskaya Str. 10 Building 8, 119121 Moscow, Russia; (L.A.K.); (Y.V.M.)
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Structural Insights into the Azole Resistance of the Candida albicans Darlington Strain Using Saccharomyces cerevisiae Lanosterol 14α-Demethylase as a Surrogate. J Fungi (Basel) 2021; 7:jof7110897. [PMID: 34829185 PMCID: PMC8621857 DOI: 10.3390/jof7110897] [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: 09/14/2021] [Revised: 10/15/2021] [Accepted: 10/19/2021] [Indexed: 11/17/2022] Open
Abstract
Target-based azole resistance in Candida albicans involves overexpression of the ERG11 gene encoding lanosterol 14α-demethylase (LDM), and/or the presence of single or multiple mutations in this enzyme. Overexpression of Candida albicans LDM (CaLDM) Y132H I471T by the Darlington strain strongly increased resistance to the short-tailed azoles fluconazole and voriconazole, and weakly increased resistance to the longer-tailed azoles VT-1161, itraconazole and posaconazole. We have used, as surrogates, structurally aligned mutations in recombinant hexahistidine-tagged full-length Saccharomyces cerevisiae LDM6×His (ScLDM6×His) to elucidate how differential susceptibility to azole drugs is conferred by LDM of the C. albicans Darlington strain. The mutations Y140H and I471T were introduced, either alone or in combination, into ScLDM6×His via overexpression of the recombinant enzyme from the PDR5 locus of an azole hypersensitive strain of S. cerevisiae. Phenotypes and high-resolution X-ray crystal structures were determined for the surrogate enzymes in complex with representative short-tailed (voriconazole) and long-tailed (itraconazole) triazoles. The preferential high-level resistance to short-tailed azoles conferred by the ScLDM Y140H I471T mutant required both mutations, despite the I471T mutation conferring only a slight increase in resistance. Crystal structures did not detect changes in the position/tilt of the heme co-factor of wild-type ScLDM, I471T and Y140H single mutants, or the Y140H I471T double-mutant. The mutant threonine sidechain in the Darlington strain CaLDM perturbs the environment of the neighboring C-helix, affects the electronic environment of the heme, and may, via differences in closure of the neck of the substrate entry channel, increase preferential competition between lanosterol and short-tailed azole drugs.
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Sitterlé E, Coste AT, Obadia T, Maufrais C, Chauvel M, Sertour N, Sanglard D, Puel A, D'Enfert C, Bougnoux ME. Large-scale genome mining allows identification of neutral polymorphisms and novel resistance mutations in genes involved in Candida albicans resistance to azoles and echinocandins. J Antimicrob Chemother 2021; 75:835-848. [PMID: 31923309 DOI: 10.1093/jac/dkz537] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/22/2019] [Accepted: 12/01/2019] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND The genome of Candida albicans displays significant polymorphism. Point mutations in genes involved in resistance to antifungals may either confer phenotypic resistance or be devoid of phenotypic consequences. OBJECTIVES To catalogue polymorphisms in azole and echinocandin resistance genes occurring in susceptible strains in order to rapidly pinpoint relevant mutations in resistant strains. METHODS Genome sequences from 151 unrelated C. albicans strains susceptible to fluconazole and caspofungin were used to create a catalogue of non-synonymous polymorphisms in genes involved in resistance to azoles (ERG11, TAC1, MRR1 and UPC2) or echinocandins (FKS1). The potential of this catalogue to reveal putative resistance mutations was tested in 10 azole-resistant isolates, including 1 intermediate to caspofungin. Selected mutations were analysed by mutagenesis experiments or mutational prediction effect. RESULTS In the susceptible strains, we identified 126 amino acid substitutions constituting the catalogue of phenotypically neutral polymorphisms. By excluding these neutral substitutions, we identified 22 additional substitutions in the 10 resistant strains. Among these substitutions, 10 had already been associated with resistance. The remaining 12 were in Tac1p (n = 6), Upc2p (n = 2) and Erg11p (n = 4). Four out of the six homozygous substitutions in Tac1p (H263Y, A790V, H839Y and P971S) conferred increases in azole MICs, while no effects were observed for those in Upc2p. Additionally, two homozygous substitutions (Y64H and P236S) had a predicted conformation effect on Erg11p. CONCLUSIONS By establishing a catalogue of neutral polymorphisms occurring in genes involved in resistance to antifungal drugs, we provide a useful resource for rapid identification of mutations possibly responsible for phenotypic resistance in C. albicans.
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Affiliation(s)
- Emilie Sitterlé
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Paris, France.,Unité de Parasitologie-Mycologie, Service de Microbiologie clinique, Hôpital Necker-Enfants-Malades, Assistance Publique des Hôpitaux de Paris (APHP), Paris, France
| | - Alix T Coste
- Institut de Microbiologie, Université de Lausanne et Centre Hospitalo-Universitaire, Lausanne, Switzerland
| | - Thomas Obadia
- Hub de Bioinformatique et Biostatistique, Département Biologie Computationnelle, Institut Pasteur, USR 3756 CNRS, Paris, France.,Unité Malaria: parasites et hôtes, Département Parasites et Insectes Vecteurs, Institut Pasteur, Paris, France
| | - Corinne Maufrais
- Hub de Bioinformatique et Biostatistique, Département Biologie Computationnelle, Institut Pasteur, USR 3756 CNRS, Paris, France
| | - Murielle Chauvel
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France
| | - Natacha Sertour
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France
| | - Dominique Sanglard
- Institut de Microbiologie, Université de Lausanne et Centre Hospitalo-Universitaire, Lausanne, Switzerland
| | - Anne Puel
- Laboratoire de génétique humaine des maladies infectieuses, Necker, INSERM U1163, Paris, France.,Université Paris Descartes, Institut Imagine, Paris, France
| | - Christophe D'Enfert
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France
| | - Marie-Elisabeth Bougnoux
- Unité Biologie et Pathogénicité Fongiques, Département de Mycologie, Institut Pasteur, USC2019 INRA, Paris, France.,Unité de Parasitologie-Mycologie, Service de Microbiologie clinique, Hôpital Necker-Enfants-Malades, Assistance Publique des Hôpitaux de Paris (APHP), Paris, France.,Université de Paris, Paris, France
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Howard KC, Dennis EK, Watt DS, Garneau-Tsodikova S. A comprehensive overview of the medicinal chemistry of antifungal drugs: perspectives and promise. Chem Soc Rev 2020; 49:2426-2480. [PMID: 32140691 DOI: 10.1039/c9cs00556k] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The emergence of new fungal pathogens makes the development of new antifungal drugs a medical imperative that in recent years motivates the talents of numerous investigators across the world. Understanding not only the structural families of these drugs but also their biological targets provides a rational means for evaluating the merits and selectivity of new agents for fungal pathogens and normal cells. An equally important aspect of modern antifungal drug development takes a balanced look at the problems of drug potency and drug resistance. The future development of new antifungal agents will rest with those who employ synthetic and semisynthetic methodology as well as natural product isolation to tackle these problems and with those who possess a clear understanding of fungal cell architecture and drug resistance mechanisms. This review endeavors to provide an introduction to a growing and increasingly important literature, including coverage of the new developments in medicinal chemistry since 2015, and also endeavors to spark the curiosity of investigators who might enter this fascinatingly complex fungal landscape.
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Affiliation(s)
- Kaitlind C Howard
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536-0596, USA.
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The Impact of Gene Dosage and Heterozygosity on The Diploid Pathobiont Candida albicans. J Fungi (Basel) 2019; 6:jof6010010. [PMID: 31892130 PMCID: PMC7151161 DOI: 10.3390/jof6010010] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 12/14/2019] [Accepted: 12/18/2019] [Indexed: 12/29/2022] Open
Abstract
Candida albicans is a fungal species that can colonize multiple niches in the human host where it can grow either as a commensal or as an opportunistic pathogen. The genome of C. albicans has long been of considerable interest, given that it is highly plastic and can undergo a wide variety of alterations. These changes play a fundamental role in determining C. albicans traits and have been shown to enable adaptation both to the host and to antifungal drugs. C. albicans isolates contain a heterozygous diploid genome that displays variation from the level of single nucleotides to largescale rearrangements and aneuploidy. The heterozygous nature of the genome is now increasingly recognized as being central to C. albicans biology, as the relative fitness of isolates has been shown to correlate with higher levels of overall heterozygosity. Moreover, loss of heterozygosity (LOH) events can arise frequently, either at single polymorphisms or at a chromosomal level, and both can alter the behavior of C. albicans cells during infection or can modulate drug resistance. In this review, we examine genome plasticity in this pathobiont focusing on how gene dosage variation and loss of heterozygosity events can arise and how these modulate C. albicans behavior.
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Can Saccharomyces cerevisiae keep up as a model system in fungal azole susceptibility research? Drug Resist Updat 2019; 42:22-34. [PMID: 30822675 DOI: 10.1016/j.drup.2019.02.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 01/30/2019] [Accepted: 02/11/2019] [Indexed: 12/14/2022]
Abstract
The difficulty of manipulation and limited availability of genetic tools for use in many pathogenic fungi hamper fast and adequate investigation of cellular metabolism and consequent possibilities for antifungal therapies. S. cerevisiae is a model organism that is used to study many eukaryotic systems. In this review, we analyse the potency and relevance of this model system in investigating fungal susceptibility to azole drugs. Although many of the concepts apply to multiple pathogenic fungi, for the sake of simplicity, we will focus on the validity of using S. cerevisiae as a model organism for two Candida species, C. albicans and C. glabrata. Apart from the general benefits, we explore how S. cerevisiae can specifically be used to improve our knowledge on azole drug resistance and enables fast and efficient screening for novel drug targets in combinatorial therapy. We consider the shortcomings of the model system, yet conclude that it is still opportune to use S. cerevisiae as a model system for pathogenic fungi in this era.
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Spettel K, Barousch W, Makristathis A, Zeller I, Nehr M, Selitsch B, Lackner M, Rath PM, Steinmann J, Willinger B. Analysis of antifungal resistance genes in Candida albicans and Candida glabrata using next generation sequencing. PLoS One 2019; 14:e0210397. [PMID: 30629653 PMCID: PMC6328131 DOI: 10.1371/journal.pone.0210397] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 12/21/2018] [Indexed: 12/13/2022] Open
Abstract
Introduction/Objectives An increase in antifungal resistant Candida strains has been reported in recent years. The aim of this study was to detect mutations in resistance genes of azole-resistant, echinocandin-resistant or multi-resistant strains using next generation sequencing technology, which allows the analysis of multiple resistance mechanisms in a high throughput setting. Methods Forty clinical Candida isolates (16 C. albicans and 24 C. glabrata strains) with MICs for azoles and echinocandins above the clinical EUCAST breakpoint were examined. The genes ERG11, ERG3, TAC1 and GSC1 (FKS1) in C. albicans, as well as ERG11, CgPDR1, FKS1 and FKS2 in C. glabrata were sequenced. Results Fifty-four different missense mutations were identified, 13 of which have not been reported before. All nine echinocandin-resistant Candida isolates showed mutations in the hot spot (HS) regions of FKS1, FKS2 or GSC1. In ERG3 two homozygous premature stop codons were identified in two highly azole-resistant and moderately echinocandin-resistant C. albicans strains. Seven point mutations in ERG11 were determined in azole-resistant C. albicans whereas in azole-resistant C. glabrata, no ERG11 mutations were detected. In 10 out of 13 azole-resistant C. glabrata, 12 different potential gain-of-function mutations in the transcription factor CgPDR1 were verified, which are associated with an overexpression of the efflux pumps CDR1/2. Conclusion This study showed that next generation sequencing allows the thorough investigation of a large number of isolates more cost efficient and faster than conventional Sanger sequencing. Targeting different resistance genes and a large sample size of highly resistant strains allows a better determination of the relevance of the different mutations, and to differentiate between causal mutations and polymorphisms.
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Affiliation(s)
- Kathrin Spettel
- Department of Laboratory Medicine, Division of Clinical Microbiology, Medical University of Vienna, Vienna, Austria
| | - Wolfgang Barousch
- Department of Laboratory Medicine, Division of Clinical Microbiology, Medical University of Vienna, Vienna, Austria
| | - Athanasios Makristathis
- Department of Laboratory Medicine, Division of Clinical Microbiology, Medical University of Vienna, Vienna, Austria
| | - Iris Zeller
- Department of Laboratory Medicine, Division of Clinical Microbiology, Medical University of Vienna, Vienna, Austria
| | - Marion Nehr
- Department of Laboratory Medicine, Division of Clinical Microbiology, Medical University of Vienna, Vienna, Austria
| | - Brigitte Selitsch
- Department of Laboratory Medicine, Division of Clinical Microbiology, Medical University of Vienna, Vienna, Austria
| | - Michaela Lackner
- Division of Hygiene and Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Peter-Michael Rath
- Institute of Medical Microbiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Joerg Steinmann
- Institute of Medical Microbiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
- Institute of Clinical Hygiene, Medical Microbiology and Infectiology, Paracelsus Medical University, Nuremberg, Germany
| | - Birgit Willinger
- Department of Laboratory Medicine, Division of Clinical Microbiology, Medical University of Vienna, Vienna, Austria
- * E-mail:
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A Transcriptomics Approach To Unveiling the Mechanisms of In Vitro Evolution towards Fluconazole Resistance of a Candida glabrata Clinical Isolate. Antimicrob Agents Chemother 2018; 63:AAC.00995-18. [PMID: 30348666 PMCID: PMC6325195 DOI: 10.1128/aac.00995-18] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 10/14/2018] [Indexed: 01/05/2023] Open
Abstract
Candida glabrata is an emerging fungal pathogen. Its increased prevalence is associated with its ability to rapidly develop antifungal drug resistance, particularly to azoles. Candida glabrata is an emerging fungal pathogen. Its increased prevalence is associated with its ability to rapidly develop antifungal drug resistance, particularly to azoles. In order to unravel new molecular mechanisms behind azole resistance, a transcriptomics analysis of the evolution of a C. glabrata clinical isolate (isolate 044) from azole susceptibility to posaconazole resistance (21st day), clotrimazole resistance (31st day), and fluconazole and voriconazole resistance (45th day), induced by longstanding incubation with fluconazole, was carried out. All the evolved strains were found to accumulate lower concentrations of azole drugs than the parental strain, while the ergosterol concentration remained mostly constant. However, only the population displaying resistance to all azoles was found to have a gain-of-function mutation in the C. glabrataPDR1 gene, leading to the upregulation of genes encoding multidrug resistance transporters. Intermediate strains, exhibiting posaconazole/clotrimazole resistance and increased fluconazole/voriconazole MIC levels, were found to display alternative ways to resist azole drugs. Particularly, posaconazole/clotrimazole resistance after 31 days was correlated with increased expression of adhesin genes. This finding led us to identify the Epa3 adhesin as a new determinant of azole resistance. Besides being required for biofilm formation, Epa3 expression was found to decrease the intracellular accumulation of azole antifungal drugs. Altogether, this work provides a glimpse of the transcriptomics evolution of a C. glabrata population toward multiazole resistance, highlighting the multifactorial nature of the acquisition of azole resistance and pointing out a new player in azole resistance.
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12
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Ali EM, Amiri A. Selection Pressure Pathways and Mechanisms of Resistance to the Demethylation Inhibitor-Difenoconazole in Penicillium expansum. Front Microbiol 2018; 9:2472. [PMID: 30429831 PMCID: PMC6220093 DOI: 10.3389/fmicb.2018.02472] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 09/27/2018] [Indexed: 11/13/2022] Open
Abstract
Penicillium expansum causes blue mold, the most economically important postharvest disease of pome fruit worldwide. Beside sanitation practices, the disease is managed through fungicide applications at harvest. Difenoconazole (DIF) is a new demethylation inhibitor (DMI) fungicide registered recently to manage postharvest diseases of pome fruit. Herein, we evaluated the sensitivity of 130 P. expansum baseline isolates never exposed to DIF and determined the effective concentration (EC50) necessary to inhibit 50% germination, germ tube length, and mycelial growth. The respective mean EC50 values of 0.32, 0.26, and 0.18 μg/ml indicate a high sensitivity of P. expansum baseline isolates to DIF. We also found full and extended control efficacy in vivo after 6 months of storage at 1°C. We conducted a risk assessment for DIF-resistance development using ultraviolet excitation combined with or without DIF-selection pressure to generate and characterize lab mutants. Fifteen DIF-resistant mutants were selected and showed EC50 values of 0.92 to 1.4 μg/ml and 1.7 to 3.8 μg/ml without and with a DIF selection pressure, respectively. Resistance to DIF was stable in vitro over a 10-week period without selection pressure. Alignment of the full CYP51 gene sequences from the three wild-type and 15 mutant isolates revealed a tyrosine to phenylalanine mutation at codon 126 (Y126F) in all of the 15 mutants but not in the wild-type parental isolates. Resistance factors increased 5 to 15-fold in the mutants compared to the wild-type-isolates. DIF-resistant mutants also displayed enhanced CYP51 expression by 2 to 14-fold and was positively correlated with the EC50 values (R 2 = 0.8264). Cross resistance between DIF and fludioxonil, the mixing-partner in the commercial product, was not observed. Our findings suggest P. expansum resistance to DIF is likely to emerge in commercial packinghouse when used frequently. Future studies will determine whether resistance to DIF is qualitative or quantitative which will be determinant in the speed at which resistance will develop and spread in commercial packinghouses and to develop appropriate strategies to extend the lifespan of this new fungicide.
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Affiliation(s)
| | - Achour Amiri
- Department of Plant Pathology, Tree Fruit Research and Extension Center, Washington State University, Wenatchee, WA, United States
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13
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Matowane RG, Wieteska L, Bamal HD, Kgosiemang IKR, Van Wyk M, Manume NA, Abdalla SMH, Mashele SS, Gront D, Syed K. In silico analysis of cytochrome P450 monooxygenases in chronic granulomatous infectious fungus Sporothrix schenckii: Special focus on CYP51. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1866:166-177. [PMID: 28989052 DOI: 10.1016/j.bbapap.2017.10.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 09/29/2017] [Accepted: 10/02/2017] [Indexed: 01/19/2023]
Abstract
Sporotrichosis is an emerging chronic, granulomatous, subcutaneous, mycotic infection caused by Sporothrix species. Sporotrichosis is treated with the azole drug itraconazole as ketoconazole is ineffective. It is a well-known fact that azole drugs act by inhibiting cytochrome P450 monooxygenases (P450s), heme-thiolate proteins. To date, nothing is known about P450s in Sporothrix schenckii and the molecular basis of its resistance to ketoconazole. Here we present genome-wide identification, annotation, phylogenetic analysis and comprehensive P450 family-level comparative analysis of S. schenckii P450s with pathogenic fungi P450s, along with a rationale for ketoconazole resistance by S. schenckii based on in silico structural analysis of CYP51. Genome data-mining of S. schenckii revealed 40 P450s in its genome that can be grouped into 32 P450 families and 39 P450 subfamilies. Comprehensive comparative analysis of P450s revealed that S. schenckii shares 11 P450 families with plant pathogenic fungi and has three unique P450 families: CYP5077, CYP5386 and CYP5696 (novel family). Among P450s, CYP51, the main target of azole drugs was also found in S. schenckii. 3D modeling of S. schenckii CYP51 revealed the presence of characteristic P450 motifs with exceptionally large reductase interaction site 2. In silico analysis revealed number of mutations that can be associated with ketoconazole resistance, especially at the channel entrance to the active site. One of possible reason for better stabilization of itraconazole, compared to ketoconazole, is that the more extended molecule of itraconazole may form a hydrogen bond with ASN-230. This in turn may explain its effectiveness against S. schenckii vis-a-vis resistant to ketoconazole. This article is part of a Special Issue entitled: Cytochrome P450 biodiversity and biotechnology, edited by Erika Plettner, Gianfranco Gilardi, Luet Wong, Vlada Urlacher, Jared Goldstone.
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Affiliation(s)
- Retshedisitswe Godfrey Matowane
- Unit for Drug Discovery Research, Department of Health Sciences, Faculty of Health and Environmental Sciences, Central University of Technology, Bloemfontein 9300, Free State, South Africa
| | - Lukasz Wieteska
- Laboratory of Theory of Biopolymers, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
| | - Hans Denis Bamal
- Unit for Drug Discovery Research, Department of Health Sciences, Faculty of Health and Environmental Sciences, Central University of Technology, Bloemfontein 9300, Free State, South Africa
| | - Ipeleng Kopano Rosinah Kgosiemang
- Unit for Drug Discovery Research, Department of Health Sciences, Faculty of Health and Environmental Sciences, Central University of Technology, Bloemfontein 9300, Free State, South Africa
| | - Mari Van Wyk
- Unit for Drug Discovery Research, Department of Health Sciences, Faculty of Health and Environmental Sciences, Central University of Technology, Bloemfontein 9300, Free State, South Africa
| | - Nessie Agnes Manume
- Unit for Drug Discovery Research, Department of Health Sciences, Faculty of Health and Environmental Sciences, Central University of Technology, Bloemfontein 9300, Free State, South Africa
| | - Sara Mohamed Hasaan Abdalla
- Unit for Drug Discovery Research, Department of Health Sciences, Faculty of Health and Environmental Sciences, Central University of Technology, Bloemfontein 9300, Free State, South Africa
| | - Samson Sitheni Mashele
- Unit for Drug Discovery Research, Department of Health Sciences, Faculty of Health and Environmental Sciences, Central University of Technology, Bloemfontein 9300, Free State, South Africa
| | - Dominik Gront
- Laboratory of Theory of Biopolymers, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
| | - Khajamohiddin Syed
- Unit for Drug Discovery Research, Department of Health Sciences, Faculty of Health and Environmental Sciences, Central University of Technology, Bloemfontein 9300, Free State, South Africa.
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14
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Chen SN, Luo CX, Hu MJ, Schnabel G. Sensitivity of Colletotrichum Species, Including C. fioriniae and C. nymphaeae, from Peach to Demethylation Inhibitor Fungicides. PLANT DISEASE 2016; 100:2434-2441. [PMID: 30686167 DOI: 10.1094/pdis-04-16-0574-re] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Few fungicides are effective against anthracnose, caused by Colletotrichum spp., and emerging resistance makes the search for chemical alternatives more relevant. Isolates of the Colletotrichum acutatum species complex were collected from South Carolina and Georgia peach orchards and phylogenetic analysis of the combined internal transcribed spacer region, glyceraldehyde-3-phosphate dehydrogenase, and β-tubulin gene sequences separated the isolates into C. nymphaeae and C. fioriniae. The sensitivity of these and three other previously reported Colletotrichum spp. from peach, including C. fructicola, C. siamense, and C. truncatum, to demethylation inhibitor (DMI) fungicides difenoconazole, propiconazole, tebuconazole, metconazole, flutriafol, and fenbuconazole was determined based upon mycelial growth inhibition. C. truncatum was resistant to tebuconazole, metconazole, flutriafol, and fenbuconazole and C. nymphaeae was resistant to flutriafol and fenbuconazole based on 50% effective concentration (EC50) values >100 μg/ml. C. fructicola and C. siamense were sensitive to all DMI fungicides (EC50 values of 0.2 to 13.1 μg/ml). C. fioriniae subgroup 2 isolates were less sensitive to DMI fungicides (EC50 values of 0.5 to 16.2 μg/ml) compared with C. fioriniae subgroup 1 (EC50 values of 0.03 to 2.1 μg/ml). Difenoconazole and propiconazole provided the best control efficacy in vitro to all five species, with EC50 values of 0.2 to 2.7 μg/ml. Tebuconazole and metconazole were effective against all Colletotrichum spp., except for C. truncatum. The strong in vitro activity of some DMI fungicides against Colletotrichum spp. may be exploited for improved anthracnose disease management of peach.
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Affiliation(s)
- S N Chen
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - C X Luo
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - M J Hu
- Department of Agricultural and Environmental Sciences, Clemson University, Clemson, SC 29634
| | - G Schnabel
- Department of Agricultural and Environmental Sciences, Clemson University, Clemson, SC 29634
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15
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Alvarez-Rueda N, Fleury A, Logé C, Pagniez F, Robert E, Morio F, Le Pape P. The amino acid substitution N136Y in Candida albicans sterol 14alpha-demethylase is involved in fluconazole resistance. Med Mycol 2016; 54:764-775. [PMID: 27143634 DOI: 10.1093/mmy/myw023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 03/24/2016] [Indexed: 12/22/2022] Open
Abstract
Resistance to fluconazole antifungal is an ongoing impediment to a successful treatment of Candida albicans infections. One of the most prevalent mechanisms leading to azole resistance is genetic alterations of the 14α-demethylase, the target of azole antifungals, through point mutations. Site-directed mutagenesis and molecular modeling of 14α-demethylase rationalize biological data about the role of protein substitutions in the azole treatment failure. In this work, we investigated the role of N136Y substitution by site-directed mutagenesis into Pichia pastoris guided by structural analysis. Single amino acid substitutions were created by site-directed mutagenesis into P. pastoris with C. albicans ERG11 gene as template. In vitro susceptibility of P. pastoris transformants expressing wild-type and mutants to azole compounds was determined by CLSI M27-A2 and spot agar methods. The fluconazole effect on ergosterol biosynthesis was analyzed by gas chromatography-mass spectrometry. By microdilution and spot tests, N136Y transformants showed a reduced in vitro susceptibility to fluconazole compared to wild-type controls. As expected, ergosterol/lanosterol ratios were higher in N136Y transformants compared to the wild-type controls after treatment with fluconazole. Molecular modeling suggests that residue Asn136 located within the first mutation hot spot, could play a role during heme and azole binding. These results provide new insights into the structural basis for 14α-demethylase-azole interaction and could guide the design of novel azole antifungals.
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Affiliation(s)
| | - Audrey Fleury
- Département de Parasitologie et de Mycologie Médicale
| | - Cédric Logé
- Laboratoire de Chimie Thérapeutique, Université de Nantes, Nantes Atlantique Universités, EA1155 - IICiMed, UFR des Sciences Pharmaceutiques et Biologiques, France
| | | | | | - Florent Morio
- Département de Parasitologie et de Mycologie Médicale.,Laboratoire de Parasitologie-Mycologie, CHU de Nantes, Nantes, France
| | - Patrice Le Pape
- Département de Parasitologie et de Mycologie Médicale.,Laboratoire de Parasitologie-Mycologie, CHU de Nantes, Nantes, France
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16
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The development of fluconazole resistance in Candida albicans – an example of microevolution of a fungal pathogen. J Microbiol 2016; 54:192-201. [DOI: 10.1007/s12275-016-5628-4] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 01/08/2016] [Accepted: 01/08/2016] [Indexed: 01/13/2023]
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17
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Shrestha SK, Fosso MY, Garneau-Tsodikova S. A combination approach to treating fungal infections. Sci Rep 2015; 5:17070. [PMID: 26594050 PMCID: PMC4655404 DOI: 10.1038/srep17070] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/23/2015] [Indexed: 12/11/2022] Open
Abstract
Azoles are antifungal drugs used to treat fungal infections such as candidiasis in humans. Their extensive use has led to the emergence of drug resistance, complicating antifungal therapy for yeast infections in critically ill patients. Combination therapy has become popular in clinical practice as a potential strategy to fight resistant fungal isolates. Recently, amphiphilic tobramycin analogues, C12 and C14, were shown to display antifungal activities. Herein, the antifungal synergy of C12 and C14 with four azoles, fluconazole (FLC), itraconazole (ITC), posaconazole (POS), and voriconazole (VOR), was examined against seven Candida albicans strains. All tested strains were synergistically inhibited by C12 when combined with azoles, with the exception of C. albicans 64124 and MYA-2876 by FLC and VOR. Likewise, when combined with POS and ITC, C14 exhibited synergistic growth inhibition of all C. albicans strains, except C. albicans MYA-2876 by ITC. The combinations of FLC-C14 and VOR-C14 showed synergistic antifungal effect against three C. albicans and four C. albicans strains, respectively. Finally, synergism between C12/C14 and POS were confirmed by time-kill and disk diffusion assays. These results suggest the possibility of combining C12 or C14 with azoles to treat invasive fungal infections at lower administration doses or with a higher efficiency.
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Affiliation(s)
- Sanjib K Shrestha
- Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY, 40536-0596, USA
| | - Marina Y Fosso
- Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY, 40536-0596, USA
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18
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Amphiphilic Tobramycin Analogues as Antibacterial and Antifungal Agents. Antimicrob Agents Chemother 2015; 59:4861-9. [PMID: 26033722 DOI: 10.1128/aac.00229-15] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 05/28/2015] [Indexed: 01/08/2023] Open
Abstract
In this study, we investigated the in vitro antifungal activities, cytotoxicities, and membrane-disruptive actions of amphiphilic tobramycin (TOB) analogues. The antifungal activities were established by determination of MIC values and in time-kill studies. Cytotoxicity was evaluated in mammalian cell lines. The fungal membrane-disruptive action of these analogues was studied by using the membrane-impermeable dye propidium iodide. TOB analogues bearing a linear alkyl chain at their 6″-position in a thioether linkage exhibited chain length-dependent antifungal activities. Analogues with C12 and C14 chains showed promising antifungal activities against tested fungal strains, with MIC values ranging from 1.95 to 62.5 mg/liter and 1.95 to 7.8 mg/liter, respectively. However, C4, C6, and C8 TOB analogues and TOB itself exhibited little to no antifungal activity. Fifty percent inhibitory concentrations (IC50s) for the most potent TOB analogues (C12 and C14) against A549 and Beas 2B cells were 4- to 64-fold and 32- to 64-fold higher, respectively, than their antifungal MIC values against various fungi. Unlike conventional aminoglycoside antibiotics, TOB analogues with alkyl chain lengths of C12 and C14 appear to inhibit fungi by inducing apoptosis and disrupting the fungal membrane as a novel mechanism of action. Amphiphilic TOB analogues showed broad-spectrum antifungal activities with minimal mammalian cell cytotoxicity. This study provides novel lead compounds for the development of antifungal drugs.
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Abstract
Invasive fungal infections remain a major source of global morbidity and mortality, especially among patients with underlying immune suppression. Successful patient management requires antifungal therapy. Yet, treatment choices are restricted due to limited classes of antifungal agents and the emergence of antifungal drug resistance. In some settings, the evolution of multidrug-resistant strains insensitive to several classes of antifungal agents is a major concern. The resistance mechanisms responsible for acquired resistance are well characterized and include changes in drug target affinity and abundance, and reduction in the intracellular level of drug by biofilms and efflux pumps. The development of high-level and multidrug resistance occurs through a stepwise evolution of diverse mechanisms. The genetic factors that influence these mechanisms are emerging and they form a complex symphony of cellular interactions that enable the cell to adapt and/or overcome drug-induced stress. Drivers of resistance involve a complex blend of host and microbial factors. Understanding these mechanisms will facilitate development of better diagnostics and therapeutic strategies to overcome and prevent antifungal resistance.
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Affiliation(s)
- David S Perlin
- Public Health Research Institute, Rutgers Biomedical and Health Sciences, New Jersey Medical School, 185 S Orange Ave, Newark, NJ 07103, USA
| | - Erika Shor
- Public Health Research Institute, Rutgers Biomedical and Health Sciences, New Jersey Medical School, 185 S Orange Ave, Newark, NJ 07103, USA
| | - Yanan Zhao
- Public Health Research Institute, Rutgers Biomedical and Health Sciences, New Jersey Medical School, 185 S Orange Ave, Newark, NJ 07103, USA
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21
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Contribution of clinically derived mutations in ERG11 to azole resistance in Candida albicans. Antimicrob Agents Chemother 2014; 59:450-60. [PMID: 25385095 DOI: 10.1128/aac.03470-14] [Citation(s) in RCA: 175] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Candida albicans, the ERG11 gene encodes lanosterol demethylase, the target of the azole antifungals. Mutations in ERG11 that result in an amino acid substitution alter the abilities of the azoles to bind to and inhibit Erg11, resulting in resistance. Although ERG11 mutations have been observed in clinical isolates, the specific contributions of individual ERG11 mutations to azole resistance in C. albicans have not been widely explored. We sequenced ERG11 in 63 fluconazole (FLC)-resistant clinical isolates. Fifty-five isolates carried at least one mutation in ERG11, and we observed 26 distinct positions in which amino acid substitutions occurred. We mapped the 26 distinct variant positions in these alleles to four regions in the predicted structure for Erg11, including its predicted catalytic site, extended fungus-specific external loop, proximal surface, and proximal surface-to-heme region. In total, 31 distinct ERG11 alleles were recovered, with 10 ERG11 alleles containing a single amino acid substitution. We then characterized 19 distinct ERG11 alleles by introducing them into the wild-type azole-susceptible C. albicans SC5314 strain and testing them for susceptibilities to FLC, itraconazole (ITC), and voriconazole (VRC). The strains that were homozygous for the single amino acid substitutions Y132F, K143R, F145L, S405F, D446E, G448E, F449V, G450E, and G464S had a ≥ 4-fold increase in FLC MIC. The strains that were homozygous for several double amino acid substitutions had decreased azole susceptibilities beyond those conferred by any single amino acid substitution. These findings indicate that mutations in ERG11 are prevalent among azole-resistant clinical isolates and that most mutations result in appreciable changes in FLC and VRC susceptibilities.
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22
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Debnath S, Addya S. Structural basis for heterogeneous phenotype of ERG11 dependent Azole resistance in C.albicans clinical isolates. SPRINGERPLUS 2014; 3:660. [PMID: 25512882 PMCID: PMC4237678 DOI: 10.1186/2193-1801-3-660] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 10/28/2014] [Indexed: 11/12/2022]
Abstract
Correlating antifungal Azole drug resistance and mis-sense mutations of ERG11 has been paradoxical in pathogenic yeast Candida albicans. Amino acid substitutions (single or multiple) are frequent on ERG11, a membrane bound enzyme of Ergosterol biosynthesis pathway. Presence or absence of mutations can not sufficiently predict susceptibility. To analyze role of mis-sense mutations on Azole resistance energetically optimized, structurally validated homology model of wild C.albicans ERG11 using eukaryotic template was generated. A Composite Search Approach is proposed to identify vital residues for interaction at 3D active site. Structural analysis of catalytic groove, dynamics of substrate access channels and proximity of Heme prosthetic group characterized ERG11 active site. Several mis-sense mutations of ERG11 reported in C.albicans clinical isolates were selected through a stringent criterion and modeled. ERG11 mutants subsequently subjected to a four tier comparative biophysical analysis. This study indicates (i) critical interactions occur with residues at anterior part of 3D catalytic groove and substitution of these vital residues alters local geometry causing considerable change in catalytic pocket dimension. (ii) Substitutions of vital residues lead to confirmed resistance in clinical isolates that may be resultant to changed geometry of catalytic pocket. (iii)These substitutions also impart significant energetic changes on C.albicans ERG11 and (iv) include detectable dynamic fluctuations on the mutants. (v)Mis-sense mutations on the vital residues of the active site and at the vicinity of Heme prosthetic group are less frequent compared to rest of the enzyme. This large scale mutational study can aid to characterize the mutants in clinical isolates.
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Affiliation(s)
- Surajit Debnath
- Department of Medical Laboratory Technology, Women's Polytechnic, Hapania, Tripura (W) India
| | - Soma Addya
- Government of West Bengal, Paschim Medinipur, West Bengal, India
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23
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Couzigou C, Gabriel F, Biteau N, Fitton-Ouhabi V, Noël T, Accoceberry I. Two missense mutations, E123Q and K151E, identified in the ERG11 allele of an azole-resistant isolate of Candida kefyr recovered from a stem cell transplant patient for acute myeloid leukemia. Med Mycol Case Rep 2014; 5:12-5. [PMID: 24936404 PMCID: PMC4052357 DOI: 10.1016/j.mmcr.2014.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 04/03/2014] [Accepted: 04/30/2014] [Indexed: 11/29/2022] Open
Abstract
We report on the first cloning and nucleotide sequencing of an ERG11 allele from a clinical isolate of Candida kefyr cross-resistant to azole antifungals. It was recovered from a stem cell transplant patient, in an oncohematology unit exhibiting unexpected high prevalence of C. kefyr. Two amino acid substitutions were identified: K151E, whose role in fluconazole resistance was already demonstrated in Candida albicans, and E123Q, a new substitution never described so far in azole-resistant Candida yeast.
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Affiliation(s)
- Célia Couzigou
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France ; Centre Hospitalier Universitaire de Bordeaux, Laboratoire de Parasitologie-Mycologie, F-33000 Bordeaux, France
| | - Frédéric Gabriel
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France ; Centre Hospitalier Universitaire de Bordeaux, Laboratoire de Parasitologie-Mycologie, F-33000 Bordeaux, France
| | - Nicolas Biteau
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Valérie Fitton-Ouhabi
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Thierry Noël
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Isabelle Accoceberry
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France ; Centre Hospitalier Universitaire de Bordeaux, Laboratoire de Parasitologie-Mycologie, F-33000 Bordeaux, France
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Rodrigues AM, de Hoog GS, de Cássia Pires D, Brihante RSN, Sidrim JJDC, Gadelha MF, Colombo AL, de Camargo ZP. Genetic diversity and antifungal susceptibility profiles in causative agents of sporotrichosis. BMC Infect Dis 2014; 14:219. [PMID: 24755107 PMCID: PMC4021050 DOI: 10.1186/1471-2334-14-219] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Accepted: 04/10/2014] [Indexed: 12/14/2022] Open
Abstract
Background Sporotrichosis is a chronic subcutaneous mycosis of humans and animals, which is typically acquired by traumatic inoculation of plant material contaminated with Sporothrix propagules, or via animals, mainly felines. Sporothrix infections notably occur in outbreaks, with large epidemics currently taking place in southeastern Brazil and northeastern China. Pathogenic species include Sporothrix brasiliensis, Sporothrix schenckii s. str., Sporothrix globosa, and Sporothrix luriei, which exhibit differing geographical distribution, virulence, and resistance to antifungals. The phylogenetically remote species Sporothrix mexicana also shows a mild pathogenic potential. Methods We assessed a genetically diverse panel of 68 strains. Susceptibility profiles of medically important Sporothrix species were evaluated by measuring the MICs and MFCs for amphotericin B (AMB), fluconazole (FLC), itraconazole (ITC), voriconazole (VRC), posaconazole (PCZ), flucytosine (5FC), and caspofungin (CAS). Haplotype networks were constructed to reveal interspecific divergences within clinical Sporothrix species to evaluate genetically deviant isolates. Results ITC and PCZ were moderately effective against S. brasiliensis (MIC90 = 2 and 2 μg/mL, respectively) and S. schenckii (MIC90 = 4 and 2 μg/mL, respectively). PCZ also showed low MICs against the rare species S. mexicana. 5FC, CAS, and FLC showed no antifungal activity against any Sporothrix species. The minimum fungicidal concentration ranged from 2 to >16 μg/mL for AMB against S. brasiliensis and S. schenckii, while the MFC90 was >16 μg/mL for ITC, VRC, and PCZ. Conclusion Sporothrix species in general showed high degrees of resistance against antifungals. Evaluating a genetically diverse panel of strains revealed evidence of multidrug resistant phenotypes, underlining the need for molecular identification of etiologic agents to predict therapeutic outcome.
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Affiliation(s)
| | | | | | | | | | | | | | - Zoilo Pires de Camargo
- Department of Microbiology, Immunology and Parasitology, Cellular Biology Division, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil.
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Mechanisms of Drug Resistance in Fungi and Their Significance in Biofilms. SPRINGER SERIES ON BIOFILMS 2014. [DOI: 10.1007/978-3-642-53833-9_4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Hill JA, Ammar R, Torti D, Nislow C, Cowen LE. Genetic and genomic architecture of the evolution of resistance to antifungal drug combinations. PLoS Genet 2013; 9:e1003390. [PMID: 23593013 PMCID: PMC3617151 DOI: 10.1371/journal.pgen.1003390] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 01/30/2013] [Indexed: 12/19/2022] Open
Abstract
The evolution of drug resistance in fungal pathogens compromises the efficacy of the limited number of antifungal drugs. Drug combinations have emerged as a powerful strategy to enhance antifungal efficacy and abrogate drug resistance, but the impact on the evolution of drug resistance remains largely unexplored. Targeting the molecular chaperone Hsp90 or its downstream effector, the protein phosphatase calcineurin, abrogates resistance to the most widely deployed antifungals, the azoles, which inhibit ergosterol biosynthesis. Here, we evolved experimental populations of the model yeast Saccharomyces cerevisiae and the leading human fungal pathogen Candida albicans with azole and an inhibitor of Hsp90, geldanamycin, or calcineurin, FK506. To recapitulate a clinical context where Hsp90 or calcineurin inhibitors could be utilized in combination with azoles to render resistant pathogens responsive to treatment, the evolution experiment was initiated with strains that are resistant to azoles in a manner that depends on Hsp90 and calcineurin. Of the 290 lineages initiated, most went extinct, yet 14 evolved resistance to the drug combination. Drug target mutations that conferred resistance to geldanamycin or FK506 were identified and validated in five evolved lineages. Whole-genome sequencing identified mutations in a gene encoding a transcriptional activator of drug efflux pumps, PDR1, and a gene encoding a transcriptional repressor of ergosterol biosynthesis genes, MOT3, that transformed azole resistance of two lineages from dependent on calcineurin to independent of this regulator. Resistance also arose by mutation that truncated the catalytic subunit of calcineurin, and by mutation in LCB1, encoding a sphingolipid biosynthetic enzyme. Genome analysis revealed extensive aneuploidy in four of the C. albicans lineages. Thus, we identify molecular determinants of the transition of azole resistance from calcineurin dependence to independence and establish multiple mechanisms by which resistance to drug combinations evolves, providing a foundation for predicting and preventing the evolution of drug resistance. Fungal infections are a leading cause of mortality worldwide and are difficult to treat due to the limited number of antifungal drugs, whose effectiveness is compromised by the emergence of drug resistance. A powerful strategy to combat drug resistance is combination therapy. Inhibiting the molecular chaperone Hsp90 or its downstream effector calcineurin cripples fungal stress responses and abrogates drug resistance. Here we provide the first analysis of the genetic and genomic changes that underpin the evolution of resistance to antifungal drug combinations in the leading human fungal pathogen, Candida albicans, and model yeast, Saccharomyces cerevisiae. We evolved experimental populations with combinations of inhibitors of Hsp90 or calcineurin and the most widely used antifungal in the clinic, the azoles, which inhibit ergosterol biosynthesis. We harnessed whole-genome sequencing to identify diverse resistance mutations among the 14 lineages that evolved resistance to the drug combination. These included mutations in genes encoding the drug targets, a transcriptional regulator of multidrug transporters, a transcriptional repressor of ergosterol biosynthesis enzymes, and a regulator of sphingolipid biosynthesis. We also identified extensive aneuploidies in several C. albicans lineages. Our study reveals multiple mechanisms by which resistance to drug combination can evolve, suggesting new strategies to combat drug resistance.
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Affiliation(s)
- Jessica A. Hill
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Ron Ammar
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - Dax Torti
- Donnelly Sequencing Centre, University of Toronto, Toronto, Ontario, Canada
| | - Corey Nislow
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - Leah E. Cowen
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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Ying Y, Zhao Y, Hu X, Cai Z, Liu X, Jin G, Zhang J, Zhang J, Liu J, Huang X. In vitro fluconazole susceptibility of 1,903 clinical isolates of Candida albicans and the identification of ERG11 mutations. Microb Drug Resist 2013; 19:266-73. [PMID: 23484590 DOI: 10.1089/mdr.2012.0204] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract Fluconazole resistance of Candida albicans has been reported to be the result of one or more specific point mutations in ERG11 gene. In this study, we amplified and sequenced the entire ERG11 coding sequence of 72 isolates of C. albicans to search for possible mutations. Twenty-seven silent mutations and 14 missense mutations were identified. While the mutations K342R and V437I were found as single-amino-acid changes in Erg11p, other mutations were detected simultaneously in individual isolates. Several different clinical isolates had the same pattern of multiple amino acid alternations: (1) A114S with Y257H was identified in 11 resistant and 3 susceptible dose-dependent isolates without any other silent mutation and may be associated with resistance; (2) Y132H combined with G450E was identified in two fluconazole-resistant isolates and is known to contribute to resistance; and (3) the coexistence of D116E, K128T, Y132H, and G465S was first described in five reduced-susceptibility isolates, but the correlation of this pattern with resistance is still uncertain. These data indicate that multiple amino acid substitutions in Erg11p were found frequently in clinical isolates and may be associated with fluconazole resistance.
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Affiliation(s)
- Ying Ying
- Department of Medical Microbiology, Nanchang University, Nanchang, People's Republic of China
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Calabrese EC, Castellano S, Santoriello M, Sgherri C, Quartacci MF, Calucci L, Warrilow AGS, Lamb DC, Kelly SL, Milite C, Granata I, Sbardella G, Stefancich G, Maresca B, Porta A. Antifungal activity of azole compounds CPA18 and CPA109 against azole-susceptible and -resistant strains of Candida albicans. J Antimicrob Chemother 2013; 68:1111-9. [PMID: 23292344 DOI: 10.1093/jac/dks506] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVES In this study we investigated the in vitro fungistatic and fungicidal activities of CPA18 and CPA109, two azole compounds with original structural features, alone and in combination with fluconazole against fluconazole-susceptible and -resistant Candida albicans strains. METHODS Antifungal activities were measured by MIC evaluation and time-kill studies. Azole binding analysis was performed by UV-Vis spectroscopy. Hyphal growth inhibition and filipin and propidium iodide staining assays were used for morphological analysis. An analysis of membrane lipids was also performed to gauge alterations in membrane composition and integrity. Synergism was calculated using fractional inhibitory concentration indices (FICIs). Evaluation of cytotoxicity towards murine macrophages was performed to verify selective antifungal activity. RESULTS Even though their binding affinity to C. albicans Erg11p is comparable to that of fluconazole, CPA compounds are active against resistant strains of C. albicans with a mutation in ERG11 sequences and/or overexpressing the ABC transporter genes CDR1 and CDR2, which encode ATP-dependent efflux pumps. Moreover, CPA18 is fungistatic, even against the two resistant strains, and was found to be synergistic with fluconazole. Differently from fluconazole and other related azoles, CPA compounds induced marked changes in membrane permeability and dramatic alterations in membrane lipid composition. CONCLUSIONS Our outcomes suggest that CPA compounds are able to overcome major mechanisms of resistance in C. albicans. Also, they are promising candidates for combination treatment that could reduce the toxicity caused by high fluconazole doses, particularly in immunocompromised patients.
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Affiliation(s)
- Elena C Calabrese
- Department of Pharmaceutical and Biomedical Sciences, University of Salerno, 84084 Fisciano, Italy
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Jiang C, Dong D, Yu B, Cai G, Wang X, Ji Y, Peng Y. Mechanisms of azole resistance in 52 clinical isolates of Candida tropicalis in China. J Antimicrob Chemother 2012; 68:778-85. [PMID: 23221625 DOI: 10.1093/jac/dks481] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
OBJECTIVES To explore the mechanisms underlying azole resistance in clinical isolates of Candida tropicalis collected in China by focusing on their efflux pumps, respiratory status and azole antifungal target enzyme. METHODS Fifty-two clinical isolates of C. tropicalis were collected from five hospitals in four provinces of China and antifungal susceptibility tests were performed. Rhodamine 6G and rhodamine 123 were used to investigate the efflux pumps and respiratory status, respectively. Transporter-related genes CDR1 and MDR1, mitochondrial gene CYTb, as well as ERG11, were quantified by real-time RT-PCR. Meanwhile, ergosterol content was analysed using liquid chromatography-mass spectrometry/mass spectrometry. An ERG11-deficient (erg11Δ) Saccharomyces cerevisiae strain was generated to study the function of mutations in ERG11. RESULTS MICs showed that 31 isolates were resistant to at least one type of azole antifungal. Flow cytometry using rhodamine 123 revealed increased respiration for the azole-resistant isolates, but CYTb was not overexpressed. No significant difference in the efflux of rhodamine 6G was found, which was consistent with the comparable expression levels of CDR1 and MDR1. In contrast, the azole-resistant isolates overexpressed ERG11 and showed increased ergosterol content. Moreover, the isolates resistant to three azole antifungals expressed higher levels of ERG11 mRNA than those resistant to only fluconazole or itraconazole. Two ERG11 mutations, Y132F and S154F, were found in azole-resistant isolates and could be shown to mediate azole resistance by expression in S. cerevisiae. CONCLUSIONS The up-regulation and mutations of ERG11 mediate azole resistance of C. tropicalis.
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Affiliation(s)
- Cen Jiang
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin No.2 Road, Shanghai 200025, China
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Ngamskulrungroj P, Chang Y, Hansen B, Bugge C, Fischer E, Kwon-Chung KJ. Characterization of the chromosome 4 genes that affect fluconazole-induced disomy formation in Cryptococcus neoformans. PLoS One 2012; 7:e33022. [PMID: 22412978 PMCID: PMC3296764 DOI: 10.1371/journal.pone.0033022] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 02/07/2012] [Indexed: 11/18/2022] Open
Abstract
Heteroresistance in Cryptococcus neoformans is an intrinsic adaptive resistance to azoles and the heteroresistant phenotype is associated with disomic chromosomes. Two chromosome 1 (Chr1) genes, ERG11, the fluconazole target, and AFR1, a drug transporter, were reported as major factors in the emergence of Chr1 disomy. In the present study, we show Chr4 to be the second most frequently formed disomy at high concentrations of fluconazole (FLC) and characterize the importance of resident genes contributing to disomy formation. We deleted nine Chr4 genes presumed to have functions in ergosterol biosynthesis, membrane composition/integrity or drug transportation that could influence Chr4 disomy under FLC stress. Of these nine, disruption of three genes homologous to Sey1 (a GTPase), Glo3 and Gcs2 (the ADP-ribosylation factor GTPase activating proteins) significantly reduced the frequency of Chr4 disomy in heteroresistant clones. Furthermore, FLC resistant clones derived from sey1Δglo3Δ did not show disomy of either Chr4 or Chr1 but instead had increased the copy number of the genes proximal to ERG11 locus on Chr1. Since the three genes are critical for the integrity of endoplasmic reticulum (ER) in Saccharomyces cerevisiae, we used Sec61ß-GFP fusion as a marker to study the ER in the mutants. The cytoplasmic ER was found to be elongated in sey1Δ but without any discernable alteration in gcs2Δ and glo3Δ under fluorescence microscopy. The aberrant ER morphology of all three mutant strains, however, was discernable by transmission electron microscopy. A 3D reconstruction using Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) revealed considerably reduced reticulation in the ER of glo3Δ and gcs2Δ strains. In sey1Δ, ER reticulation was barely detectable and cisternae were expanded extensively compared to the wild type strains. These data suggest that the genes required for maintenance of ER integrity are important for the formation of disomic chromosomes in C. neoformans under azole stress.
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Affiliation(s)
- Popchai Ngamskulrungroj
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Yun Chang
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Bryan Hansen
- Electron Microscopy Unit, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Cliff Bugge
- FEI Company, Hillsboro, Oregon, United States of America
| | - Elizabeth Fischer
- Electron Microscopy Unit, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Kyung J. Kwon-Chung
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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Possible inhibitory molecular mechanism of farnesol on the development of fluconazole resistance in Candida albicans biofilm. Antimicrob Agents Chemother 2011; 56:770-5. [PMID: 22106223 DOI: 10.1128/aac.05290-11] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Candida albicans biofilm infections are usually treated with azole antifungals such as fluconazole. However, the development of resistance to this drug in C. albicans biofilms is very common, especially in immunocompromised individuals. The upregulation of the sterol biosynthetic pathway gene ERG and the efflux pump genes CDR and MDR may contribute to this azole tolerance in Candida species. We hypothesize that farnesol, an endogenous quorum sensing molecule with possible antimicrobial properties which is also the precursor of ergosterols in C. albicans, may interfere with the development of fluconazole resistance in C. albicans biofilms. To test this hypothesis, MICs were compared and morphology changes were observed by confocal laser scanning microscopy (CLSM) for farnesol-treated and -untreated and fluconazole-resistant groups. The expression of possible target genes (ERG11, ERG25, ERG6, ERG5, ERG3, ERG1, MDR1, CDR1, and CDR2) in biofilms was analyzed by reverse transcription-PCR (RT-PCR) and quantitative PCR (qPCR) to investigate the molecular mechanisms of the inhibitory effects of farnesol. The results showed a decreased MIC of fluconazole and thinner biofilms for the farnesol-treated group, indicating that farnesol inhibited the development of fluconazole resistance. The sterol biosynthetic pathway may contribute to the inhibitory effects of farnesol, as the transcription levels of the ERG11, ERG25, ERG6, ERG3, and ERG1 genes decreased in the farnesol-treated group.
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Diagnosis of Antifungal Drug Resistance Mechanisms in Fungal Pathogens: Transcriptional Gene Regulation. CURRENT FUNGAL INFECTION REPORTS 2011. [DOI: 10.1007/s12281-011-0055-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Identification and characterization of four azole-resistant erg3 mutants of Candida albicans. Antimicrob Agents Chemother 2010; 54:4527-33. [PMID: 20733039 DOI: 10.1128/aac.00348-10] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sterol analysis identified four Candida albicans erg3 mutants in which ergosta 7,22-dienol, indicative of perturbations in sterol Δ(5,6)-desaturase (Erg3p) activity, comprised >5% of the total sterol fraction. The erg3 mutants (CA12, CA488, CA490, and CA1008) were all resistant to fluconazole, voriconazole, itraconazole, ketoconazole, and clotrimazole under standard CLSI assay conditions (MIC values, ≥256, 16, 16, 8, and 1 μg ml⁻¹, respectively). Importantly, CA12 and CA1008 retained an azole-resistant phenotype even when assayed in the presence of FK506, a multidrug efflux inhibitor. Conversely, CA488, CA490, and three comparator isolates (CA6, CA14, and CA177, in which ergosterol comprised >80% of the total sterol fraction and ergosta 7,22-dienol was undetectable) all displayed azole-sensitive phenotypes under efflux-inhibited assay conditions. Owing to their ergosterol content, CA6, CA14, and CA177 were highly sensitive to amphotericin B (MIC values, <0.25 μg ml⁻¹); CA1008, in which ergosterol comprised <2% of the total sterol fraction, was less sensitive (MIC, 1 μg ml⁻¹). CA1008 harbored multiple amino acid substitutions in Erg3p but only a single conserved polymorphism (E266D) in sterol 14α-demethylase (Erg11p). CA12 harbored one substitution (W332R) in Erg3p and no residue changes in Erg11p. CA488 and CA490 were found to harbor multiple residue changes in both Erg3p and Erg11p. The results suggest that missense mutations in ERG3 might arise in C. albicans more frequently than currently supposed and that the clinical significance of erg3 mutants, including those in which additional mechanisms also contribute to resistance, should not be discounted.
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Kim TH, Lee MK. Evaluation of the V404I and V509M amino acid substitutions of ERG11 gene in Candida albicans isolates by pyrosequencing. Folia Microbiol (Praha) 2010; 55:301-4. [PMID: 20526846 DOI: 10.1007/s12223-010-0045-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Revised: 02/04/2010] [Indexed: 11/24/2022]
Abstract
The molecular mechanisms underlying fluconazole resistance in C. albicans involve mutations and the overexpression of the ERG11 gene and membrane transport proteins. We examined the relationship between the reduced fluconazole susceptibility of C. albicans and mutations of V404I and V509M in the ERG11 gene in 182 C. albicans clinical isolates using the Pyrosequencing method. DNAs from these clinical isolates with different levels of in-vitro fluconazole susceptibility--one resistant, five susceptible dose-dependent (SDD), four trailer, and 172 susceptible--were analyzed. None of the fluconazole-susceptible, SDD, trailer or resistant isolates had mutations of V404I or V509M. Our results showed that no correlation can be found between the V404I or V509M mutation and fluconazole susceptibility in C. albicans.
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Affiliation(s)
- T-H Kim
- Department of Urology, Chung-Ang University College of Medicine, Seoul, Korea
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Morio F, Loge C, Besse B, Hennequin C, Le Pape P. Screening for amino acid substitutions in the Candida albicans Erg11 protein of azole-susceptible and azole-resistant clinical isolates: new substitutions and a review of the literature. Diagn Microbiol Infect Dis 2010; 66:373-84. [PMID: 20226328 DOI: 10.1016/j.diagmicrobio.2009.11.006] [Citation(s) in RCA: 191] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2009] [Revised: 11/07/2009] [Accepted: 11/12/2009] [Indexed: 11/29/2022]
Abstract
For several years, azole antifungal drugs have been a treatment option for potentially life-threatening Candida infections. However, azole resistance can occur through various mechanisms such as alterations in ERG11, encoding lanosterol 14alpha-demethylase (CYP51). In this study, we investigated the antifungal susceptibility to fluconazole, itraconazole, and voriconazole of 73 clinical isolates of Candida albicans. Screening for amino acid substitutions in Erg11 was performed on each of the 73 isolates. Twenty isolates displayed a marked decrease in azole susceptibility. Amino acid substitutions were detected in more than two-thirds of the strains. In all, 23 distinct substitutions were identified. Four have not been described previously, among which N136Y and Y447H are suspected to be involved in azole resistance. We suggest that the high genetic polymorphism of ERG11 must be considered in the rationale design of new azole compounds targeting lanosterol 14alpha-demethylase. A review of all Erg11 amino acid polymorphisms described to date is given.
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Affiliation(s)
- Florent Morio
- Université de Nantes, Nantes Atlantique Universités, Département de Parasitologie et Mycologie Médicale, EA 1155-IICiMed, Faculté de Pharmacie, 1 Rue Gaston Veil, 44035 Nantes, France
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Sanglard D, Coste A, Ferrari S. Antifungal drug resistance mechanisms in fungal pathogens from the perspective of transcriptional gene regulation. FEMS Yeast Res 2009; 9:1029-50. [PMID: 19799636 DOI: 10.1111/j.1567-1364.2009.00578.x] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Fungi are primitive eukaryotes and have adapted to a variety of niches during evolution. Some fungal species may interact with other life forms (plants, insects, mammals), but are considered as pathogens when they cause mild to severe diseases. Chemical control strategies have emerged with the development of several drugs with antifungal activity against pathogenic fungi. Antifungal agents have demonstrated their efficacy by improving patient health in medicine. However, fungi have counteracted antifungal agents in several cases by developing resistance mechanisms. These mechanisms rely on drug resistance genes including multidrug transporters and drug targets. Their regulation is crucial for the development of antifungal drug resistance and therefore transcriptional factors critical for their regulation are being characterized. Recent genome-wide studies have revealed complex regulatory circuits involving these genetic and transcriptional regulators. Here, we review the current understanding of the transcriptional regulation of drug resistance genes from several fungal pathogens including Candida and Aspergillus species.
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Affiliation(s)
- Dominique Sanglard
- Institute of Microbiology, University of Lausanne and University Hospital Center, 1011 Lausanne, Switzerland.
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Wang H, Kong F, Sorrell TC, Wang B, McNicholas P, Pantarat N, Ellis D, Xiao M, Widmer F, Chen SC. Rapid detection of ERG11 gene mutations in clinical Candida albicans isolates with reduced susceptibility to fluconazole by rolling circle amplification and DNA sequencing. BMC Microbiol 2009; 9:167. [PMID: 19682357 PMCID: PMC2782262 DOI: 10.1186/1471-2180-9-167] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2009] [Accepted: 08/14/2009] [Indexed: 11/21/2022] Open
Abstract
Background Amino acid substitutions in the target enzyme Erg11p of azole antifungals contribute to clinically-relevant azole resistance in Candida albicans. A simple molecular method for rapid detection of ERG11 gene mutations would be an advantage as a screening tool to identify potentially-resistant strains and to track their movement. To complement DNA sequencing, we developed a padlock probe and rolling circle amplification (RCA)-based method to detect a series of mutations in the C. albicans ERG11 gene using "reference" azole-resistant isolates with known mutations. The method was then used to estimate the frequency of ERG11 mutations and their type in 25 Australian clinical C. albicans isolates with reduced susceptibility to fluconazole and in 23 fluconazole-susceptible isolates. RCA results were compared DNA sequencing. Results The RCA assay correctly identified all ERG11 mutations in eight "reference" C. albicans isolates. When applied to 48 test strains, the RCA method showed 100% agreement with DNA sequencing where an ERG11 mutation-specific probe was used. Of 20 different missense mutations detected by sequencing in 24 of 25 (96%) isolates with reduced fluconazole susceptibility, 16 were detected by RCA. Five missense mutations were detected by both methods in 18 of 23 (78%) fluconazole-susceptible strains. DNA sequencing revealed that mutations in non-susceptible isolates were all due to homozygous nucleotide changes. With the exception of the mutations leading to amino acid substitution E266D, those in fluconazole-susceptible strains were heterozygous. Amino acid substitutions common to both sets of isolates were D116E, E266D, K128T, V437I and V488I. Substitutions unique to isolates with reduced fluconazole susceptibility were G464 S (n = 4 isolates), G448E (n = 3), G307S (n = 3), K143R (n = 3) and Y123H, S405F and R467K (each n = 1). DNA sequencing revealed a novel substitution, G450V, in one isolate. Conclusion The sensitive RCA assay described here is a simple, robust and rapid (2 h) method for the detection of ERG11 polymorphisms. It showed excellent concordance with ERG11 sequencing and is a potentially valuable tool to track the emergence and spread of azole-resistant C. albicans and to study the epidemiology of ERG11 mutations. The RCA method is applicable to the study of azole resistance in other fungi.
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Affiliation(s)
- Huiping Wang
- Department of Dermatology, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, PR China.
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Reliability of the Vitek 2 yeast susceptibility test for detection of in vitro resistance to fluconazole and voriconazole in clinical isolates of Candida albicans and Candida glabrata. J Clin Microbiol 2009; 47:1927-30. [PMID: 19403774 DOI: 10.1128/jcm.02070-08] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Vitek 2 yeast susceptibility test was evaluated by testing 122 Candida isolates against fluconazole and voriconazole. Excellent categorical agreement with the CLSI broth microdilution method was observed (97.5% for both the azoles). Moreover, the Vitek 2 system was able to identify all but 2 of 59 investigated fluconazole-resistant organisms.
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Nes WD, Zhou W, Ganapathy K, Liu J, Vatsyayan R, Chamala S, Hernandez K, Miranda M. Sterol 24-C-methyltransferase: An enzymatic target for the disruption of ergosterol biosynthesis and homeostasis in Cryptococcus neoformans. Arch Biochem Biophys 2009; 481:210-8. [DOI: 10.1016/j.abb.2008.11.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 10/30/2008] [Accepted: 11/01/2008] [Indexed: 10/21/2022]
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Luo CX, Schnabel G. The cytochrome P450 lanosterol 14alpha-demethylase gene is a demethylation inhibitor fungicide resistance determinant in Monilinia fructicola field isolates from Georgia. Appl Environ Microbiol 2008; 74:359-66. [PMID: 18024679 PMCID: PMC2223246 DOI: 10.1128/aem.02159-07] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Accepted: 11/06/2007] [Indexed: 11/20/2022] Open
Abstract
Resistance in Monilinia fructicola to demethylation inhibitor (DMI) fungicides is beginning to emerge in North America, but its molecular basis is unknown. Two potential genetic determinants of DMI fungicide resistance including the 14alpha-demethylase gene (MfCYP51) and the ATP-binding cassette transporter gene MfABC1, were investigated in six resistant (DMI-R) and six sensitive (DMI-S) field isolates. No point mutations leading to an amino acid change were found in the MfCYP51 gene. The constitutive expression of the MfCYP51 gene in DMI-R isolates was significantly higher compared to DMI-S isolates. Gene expression was not induced in mycelium of DMI-R or DMI-S isolates treated with 0.3 mug of propiconazole/ml. A slightly higher average MfCYP51 copy number value was detected in DMI-R isolates (1.35) compared to DMI-S isolates (1.13); however, this difference could not be verified in Southern hybridization experiments or explain the up to 11-fold-increased MfCYP51 mRNA levels in DMI-R isolates. Analysis of the upstream nucleotide sequence of the MfCYP51 gene revealed a unique 65-bp repetitive element at base pair position -117 from the translational start site in DMI-R isolates but not in DMI-S isolates. This repetitive element contained a putative promoter and was named Mona. The link between Mona and the DMI resistance phenotype became even more apparent after studying the genetic diversity between the isolates. In contrast to DMI-S isolates, DMI-R isolates contained an MfCYP51 gene of identical nucleotide sequence associated with Mona. Still, DMI-R isolates were not genetically identical as revealed by Microsatellite-PCR analysis. Also, real-time PCR analysis of genomic DNA indicated that the relative copy number of Mona among DMI-S and DMI-R isolates varied, suggesting its potential for mobility. Interestingly, constitutive expression of the MfABC1 gene in DMI-R isolates was slightly lower than that of DMI-S isolates, but expression of the MfABC1 gene in DMI-R isolates was induced in mycelium after propiconazole treatment. Therefore, the MfABC1 gene may play a minor role in DMI fungicide resistance in M. fructicola. Our results strongly suggest that overexpression of the MfCYP51 gene is an important mechanism in conferring DMI fungicide resistance in M. fructicola field isolates from Georgia and that this overexpression is correlated with Mona located upstream of the MfCYP51 gene.
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Affiliation(s)
- Chao-Xi Luo
- Department of Entomology, Soils, and Plant Sciences, Clemson University, 120 Long Hall, Clemson, SC 29634, USA
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41
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Mellado E, Garcia-Effron G, Alcázar-Fuoli L, Melchers WJG, Verweij PE, Cuenca-Estrella M, Rodríguez-Tudela JL. A new Aspergillus fumigatus resistance mechanism conferring in vitro cross-resistance to azole antifungals involves a combination of cyp51A alterations. Antimicrob Agents Chemother 2007; 51:1897-904. [PMID: 17371828 PMCID: PMC1891382 DOI: 10.1128/aac.01092-06] [Citation(s) in RCA: 366] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fourteen Aspergillus fumigatus clinical isolates that exhibited a pattern of reduced susceptibility to triazole drugs were analyzed. The sequences of the cyp51A gene from all isolates showed the presence of a point mutation at t364a, which led to the substitution of leucine 98 for histidine (L98H), together with the presence of two copies of a 34-bp sequence in tandem in the promoter of the cyp51A gene. Quantitative expression analysis (real-time PCR) showed up to an eightfold increase in the level of expression of the cyp51A gene compared to that by the susceptible strain. Three PCR fragments of one azole-resistant strain (strain CM2627) that included the promoter with the tandem repeat and part of cyp51A with the t364a mutation or PCR fragments with only one of the modifications were used to replace the cyp51A gene of an azole drug-susceptible A. fumigatus wild-type strain (strain CM237). Only transformants which had incorporated the tandem repeat in the promoter of the cyp51A gene and the L98H amino acid substitution exhibited similarly reduced patterns of susceptibility to all triazole agents and similarly increased levels of cyp51A expression, confirming that the combination of both alterations was responsible for the azole-resistant phenotype.
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Affiliation(s)
- E Mellado
- Servicio de Micologia, Centro Nacional de Microbiologia, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo Km2, 28220 Madrid, Spain.
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42
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Chen SH, Sheng CQ, Xu XH, Jiang YY, Zhang WN, He C. Identification of Y118 Amino Acid Residue in Candida albicans Sterol 14.ALPHA.-Demethylase Associated with the Enzyme Activity and Selective Antifungal Activity of Azole Analogues. Biol Pharm Bull 2007; 30:1246-53. [PMID: 17603162 DOI: 10.1248/bpb.30.1246] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our previous publication established a model to predict that the phenyl group of the C-3 side chain of azole antifungal compounds interacts with the phenol group of Tyr118 through the formation of pi-pi face-to-edge interaction. To verify this prediction, wild type and three site-directed mutants of the Y118 residue of Candida albicans sterol 14alpha-demethylase P450 (CACYP51) were constructed and heterologously expressed in Saccharomyces cerevisiae with deletion of the CYP51 gene. With the strains obtained and microsome enzymes separated, cell susceptibility and CACYP51 activity were examined with the 5 novel azole compounds based on the molecular modeling in comparison with fluconazole. After alteration of Y118 with Y118A, Y118F, and Y118T by a single base substitution, the expression levels of CACYP51 protein were not affected. However, these mutations markedly decreased its catalytic activity respectively; the mutation changes also decreased azole susceptibility, indicating the structural importance of the Y118 residue in maintaining CACYP51 activity and in determining azole susceptibility. In addition, our synthetic compounds with the phenyl group side chain attached to C3 produced higher susceptibility against S. cerevisiae with expression of CACYP51 and exhibited more potent inhibitory effects on CACYP51 activity in comparison with fluconazole, suggesting that the phenyl group of C3 side chain substitutes is also important for selective binding to target enzymes.
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Affiliation(s)
- Shuang-Hong Chen
- Naval Medical Research Institute, Xiangying Road, Shanghai, PR China
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43
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Mellado E, Alcazar-Fuoli L, García-Effrón G, Alastruey-Izquierdo A, Cuenca-Estrella M, Rodríguez-Tudela JL. New resistance mechanisms to azole drugs in Aspergillus fumigatus and emergence of antifungal drugs-resistant A. fumigatus atypical strains. Med Mycol 2006; 44:S367-S371. [PMID: 30408931 DOI: 10.1080/13693780600902243] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Azole drug resistance in Aspergillus fumigatus is an uncommon but well-known phenomenon. The analysis of resistance mechanisms at molecular level has identified the bases for A. fumigatus azole resistance. To date, the most prevalent mechanism of azole resistance appears to be the modification of Cyp51, specifically mutations in cyp51A gene. These mutations have been associated with three different antifungal susceptibility profiles: (i) cross-resistance to itraconazole and posaconazole that has been associated with amino acid substitutions at glycine 54 (G54), (ii) elevated MICs to all azole drugs associated with amino acid substitutions at methionine M220, and (iii) cross-resistance to all azole drugs related to the presence of Cyp51A substitutions at leucine 98 for histidine (L98H) linked to a duplication in tandem of a 34 bp repeat in the cyp51A promoter region, which seem to be responsible for increased cyp51A gene expression. Another matter of concern is the increasing reports of isolation of genetic variants of A. fumigatus, originally misidentified as poorly sporulating strains of A. fumigauts, as a causative agents of invasive infection. Many of these isolates belonging to the Aspergillus section Fumigati have been found to be resistant in vitro to multiple antifungal drugs. Current data show that susceptibility profile of these variants could be predictable depending on the species. Resistance among clinical strains of filamentous fungi may become more common in the future associated with the spread of prophylaxis, pre-emptive treatments and specific therapies with antifungal agents.
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Affiliation(s)
- E Mellado
- Servicio de Micología, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - L Alcazar-Fuoli
- Servicio de Micología, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - G García-Effrón
- Servicio de Micología, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - A Alastruey-Izquierdo
- Servicio de Micología, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - M Cuenca-Estrella
- Servicio de Micología, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - J L Rodríguez-Tudela
- Servicio de Micología, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
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44
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Chau AS, Gurnani M, Hawkinson R, Laverdiere M, Cacciapuoti A, McNicholas PM. Inactivation of sterol Delta5,6-desaturase attenuates virulence in Candida albicans. Antimicrob Agents Chemother 2005; 49:3646-51. [PMID: 16127034 PMCID: PMC1195422 DOI: 10.1128/aac.49.9.3646-3651.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two clinical Candida albicans isolates that exhibited high-level resistance to azoles and modest decreases in susceptibility to amphotericin B were cultured from unrelated patients. Both isolates harbored homozygous nonsense mutations in ERG3, which encodes an enzyme, sterol Delta5,6-desaturase, involved in ergosterol synthesis. Extraction and analysis of the sterols from both isolates confirmed the absence of sterol Delta5,6-desaturase activity. Although the loss of sterol Delta5,6-desaturase activity is known to confer resistance to azoles, this mechanism of resistance has rarely been seen in clinical isolates, suggesting that such mutants are at a competitive disadvantage. To test this hypothesis, the virulence of the erg3 mutants was assayed by using a mouse systemic infection model. The mutants were significantly less virulent than the wild-type comparator strains. However, the kidney fungal burdens in mice infected with the erg3 mutants were similar to those in mice infected with the wild-type strains. Similar results were obtained by using a laboratory-generated homozygous erg3 deletion mutant (D. Sanglard et al., Antimicrob. Agents Chemother. 47:2404-2412, 2003). Reintroduction of a wild-type ERG3 allele into the homozygous deletion mutant restored virulence, ergosterol synthesis, and susceptibility to azoles, confirming that these phenotypic changes were solely due to the inactivation of Erg3p.
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Affiliation(s)
- Andrew S Chau
- Schering Plough Research Institute, K15-4-4700, 2015 Galloping Hill Road, Kenilworth, NJ 07033.
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45
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Single amino acid exchanges in FAD-binding domains of squalene epoxidase of Saccharomyces cerevisiae lead to either loss of functionality or terbinafine sensitivity. Biochem Soc Trans 2005. [DOI: 10.1042/bst0331197] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Squalene epoxidase (Erg1p) is an essential enzyme in the ergosterol biosynthesis pathway in yeast. For its enzymatic activity, Erg1p requires molecular oxygen, NAD(P)H and FAD. Amino acid analysis and sequence alignment with other squalene epoxidases revealed two highly conserved FAD-binding domains, FAD I and FAD II. By random PCR mutagenesis of the ERG1 gene, one erg1 allele was isolated that carries a mutation leading to a single amino acid exchange in the FAD I domain close to the N-terminus of Erg1p. This erg1 allele codes for functional squalene epoxidase and renders yeast cells hypersensitive to terbinafine. Amino acid exchanges of other conserved residues in the FAD I and FAD II regions either led to non-functional squalene epoxidase or to the formation of squalene epoxidase with wild-type properties. These results describe the importance of specific amino acids for enzymatic activity in the yeast squalene epoxidase Erg1p.
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Abstract
Candida dubliniensis is a recently described species of pathogenic yeast that shares many phenotypic features with Candida albicans. It is primarily associated with oral colonization and infection in HIV-infected individuals. Isolates of C. dubliniensis are generally susceptible to commonly used azole antifungal agents; however, resistance has been observed in clinical isolates and can be induced by in vitro exposure. Molecular mechanisms of azole resistance in C. dubliniensis include increased drug efflux, modifications of the target enzyme and alterations in the ergosterol biosynthetic pathway.
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47
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Abstract
Much progress has been made in the last decade in identifying genes responsible for antifungal resistance in Candida albicans. Attention has focused on five major C. albicans genes: ABC transporter genes CDR1 and CDR2, major facilitator efflux gene MDR1, and ergosterol biosynthesis genes ERG11 and ERG3. Resistance involves mutations in 14C-lanosterol demethylase, targeted by fluconazole (FLZ) and encoded by ERG11, and mutations that up-regulate efflux genes that probably efflux the antifungals. Mutations that affect ERG3 mutations have been understudied as mechanism resistance among clinical isolates. In vitro resistance in clinical isolates typically involves step-wise mutations affecting more than one of these genes, and often unidentified genes. Different approaches are needed to identify these other genes. Very little is understood about reversible adaptive resistance of C. albicans despite its potential clinical significance; most clinical failures to control infections other than oropharyngeal candidiasis (OPC) occur with in vitro susceptible strains. Tolerance of C. albicans to azoles has been attributed to the calcineurin stress-response pathway, offering new potential targets for next generation antifungals. Recent studies have identified genes that regulate CDR1 or ERG genes. The focus of this review is C. albicans, although information on Saccharomyces cerevisiae or Candida glabrata is provided in areas in where Candida research is underdeveloped. With the completion of the C. albicans genomic sequence, and new methods for high throughput gene overexpression and disruption, rapid progress towards understanding the regulation of resistance, novel resistance mechanisms, and adaptive resistance is expected in the near future.
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Affiliation(s)
- Robert A Akins
- Wayne State University School of Medicine, Departments of Biochemistry & Molecular Biology, 540 East Canfield, Detroit, Michigan 48201, USA.
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48
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Osborne CS, Leitner I, Favre B, Ryder NS. Amino acid substitution in Trichophyton rubrum squalene epoxidase associated with resistance to terbinafine. Antimicrob Agents Chemother 2005; 49:2840-4. [PMID: 15980358 PMCID: PMC1168638 DOI: 10.1128/aac.49.7.2840-2844.2005] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
There has only been one clinically confirmed case of terbinafine resistance in dermatophytes, where six sequential Trichophyton rubrum isolates from the same patient were found to be resistant to terbinafine and cross-resistant to other squalene epoxidase (SE) inhibitors. Microsomal SE activity from these resistant isolates was insensitive to terbinafine, suggesting a target-based mechanism of resistance (B. Favre, M. Ghannoum, and N. S. Ryder, Med. Mycol. 42:525-529, 2004). In this study, we have characterized at the molecular level the cause of the resistant phenotype of these clinical isolates. Cloning and sequencing of the SE gene and cDNA from T. rubrum revealed the presence of an intron in the gene and an open reading frame encoding a protein of 489 residues, with an equivalent similarity (57%) to both yeast and mammalian SEs. The nucleotide sequences of SE from two terbinafine-susceptible strains were identical whereas those of terbinafine-resistant strains, serially isolated from the same patient, each contained the same single missense introducing the amino acid substitution L393F. Introduction of the corresponding substitution in the Candida albicans SE gene (L398F) and expression of this gene in Saccharomyces cerevisiae conferred a resistant phenotype to the transformants when compared to those expressing the wild-type sequence. Terbinafine resistance in these T. rubrum clinical isolates appears to be due to a single amino acid substitution in SE.
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Affiliation(s)
- Colin S Osborne
- Infectious Diseases, Novartis Institutes for BioMedical Research, Vienna, Austria.
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49
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Favre B, Ghannoum MA, Ryder NS. Biochemical characterization of terbinafine-resistant Trichophyton rubrum isolates. Med Mycol 2005; 42:525-9. [PMID: 15682641 DOI: 10.1080/13693780410001661482] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
We investigated the biochemical basis for resistance in six sequential clinical isolates of Trichophyton rubrum, from the same patient, which exhibited high-level primary resistance to terbinafine. Cellular ergosterol biosynthesis was measured by incorporation of [14C]acetate, and microsomal squalene epoxidase was assayed by conversion of [3H]squalene to squalene epoxide and lanosterol. Direct comparison was made with a terbinafine-susceptible reference strain of T. rubrum in which squalene epoxidase was previously studied. Resistant isolates displayed normal cellular ergosterol biosynthesis, although slight accumulation of radiolabeled squalene suggested reduced squalene epoxidase activity. Ergosterol biosynthesis in the resistant isolates was only inhibited by terbinafine concentrations above 1 microg/ml (IC50 5 microg/ml). In the reference strain, ergosterol biosynthesis was eliminated by terbinafine at 0.03 microg/ml in accordance with historical data. There was no significant difference in sensitivity between the six resistant isolates. Squalene epoxidase from resistant strains was three orders of magnitude less sensitive than normal enzyme to terbinafine (IC50 of 30 micromol/l and 19 n mol/l respectively). The epoxidase in the resistant strains was also unresponsive to tolnaftate. Resistance to terbinafine in these T. rubrum isolates appears to be due to alterations in the squalene epoxidase gene or a factor essential for its activity.
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Takahata S, Okutomi T, Ohtsuka K, Hoshiko S, Uchida K, Yamaguchi H. In vitroandin vivoantifungal activities of FX0685, a novel triazole antifungal agent with potent activity against fluconazole-resistantCandida albicans. Med Mycol 2005; 43:227-33. [PMID: 16010849 DOI: 10.1080/13693780410001731600] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
To evaluate the therapeutic potential of FX0685, a new triazole antifungal agent, for the treatment of opportunistic fungal infections, particularly systemic candidiasis and aspergillosis, in vitro and in vivo studies were performed using fluconazole (FLC), itraconazole (ITC) and/or amphotericin B (AMB) as reference drugs. A preliminary in vitro study showed that the antifungal activity of FX0685 against FLC-susceptible Candida albicans, several non-C. albicans Candida species and Cryptococcus neoformans was superior to that of FLC and comparable or superior to those of ITC and AMB, while the anti-Aspergillus fumigatus activity of FX0685 was to varying degrees lower than that of ITC. FX0685 appeared to be comparable to FLC and ITC in the treatment of murine systemic C. albicans and pulmonary A. fumigatus infection, respectively. The biological property of FX0685 was characterized by its potent in vitro and in vivo activity against FLC-resistant C. albicans. Part of this unique property was explained by the finding that it retained potent inhibitory activity against those CYP51 molecules in which amino acid substitutions confer a phenotype of resistance to FLC and some other azole derivatives. All of these results lead to the possibility that FX0685 may be a potential antifungal drug candidate for the treatment of various clinical forms of systemic candidiasis, including those caused by FLC-resistant C. albicans, as well as for the treatment of pulmonary aspergillosis.
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Affiliation(s)
- Sho Takahata
- Pharmaceutical Research Department, Meiji Seika Kaisha Ltd, Kohoku-ku, Yokohama, Japan.
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