scholarly journals A Systematic Screen Reveals a Diverse Collection of Medications That Induce Antifungal Resistance inCandidaSpecies

2019 ◽  
Vol 63 (5) ◽  
Author(s):  
Arielle Butts ◽  
Parker Reitler ◽  
Andrew T. Nishimoto ◽  
Christian DeJarnette ◽  
Leanna R. Estredge ◽  
...  
Keyword(s):  
Treatment Failure ◽  
Amphotericin B ◽  
Fungal Infections ◽  
Antifungal Drugs ◽  
Azole Resistance ◽  
Surface Mode ◽  
Drug Efflux ◽  
Content Type ◽  
Zinc Cluster ◽  
Antagonistic Interactions

ABSTRACTThe increasing incidence of and high mortality rates associated with invasive fungal infections (IFIs) impose an enormous clinical, social, and economic burden on humankind. In addition to microbiological resistance to existing antifungal drugs, the large number of unexplained treatment failures is a serious concern. Due to the extremely limited therapeutic options available, it is critical to identify and understand the various causes of treatment failure if patient outcomes are to improve. In this study, we examined one potential source of treatment failure: antagonistic drug interactions. Using a simple screen, we systematically identified currently approved medications that undermine the antifungal activity of three major antifungal drugs—fluconazole, caspofungin, and amphotericin B—on four prevalent human fungal pathogens—Candida albicans,Candida glabrata,Candida parapsilosis, andCandida tropicalis. This revealed that a diverse collection of structurally distinct drugs exhibit antagonistic interactions with fluconazole. Several antagonistic agents selected for follow-up studies induce azole resistance through a mechanism that depends on Tac1p/Pdr1p zinc-cluster transcription factors, which activate the expression of drug efflux pumps belonging to the ABC-type transporter family. Few antagonistic interactions were identified with caspofungin or amphotericin B, possibly reflecting their cell surface mode of action that should not be affected by drug efflux mechanisms. Given that patients at greatest risk of IFIs usually receive a multitude of drugs to treat various underlying conditions, these studies suggest that chemically inducible azole resistance may be much more common and important than previously realized.

scholarly journals Transcription Factor ADS-4 Regulates Adaptive Responses and Resistance to Antifungal Azole Stress

2015 ◽  
Vol 59 (9) ◽  
pp. 5396-5404 ◽  
Author(s):  
Kangji Wang ◽  
Zhenying Zhang ◽  
Xi Chen ◽  
Xianyun Sun ◽  
Cheng Jin ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Efflux Pump ◽  
Fungal Infections ◽  
Antifungal Drugs ◽  
Bzip Transcription Factor ◽  
Azole Resistance ◽  
Homologous Gene ◽  
Adaptive Responses ◽  
Transcriptional Responses ◽  
Content Type

ABSTRACTAzoles are commonly used as antifungal drugs or pesticides to control fungal infections in medicine and agriculture. Fungi adapt to azole stress by rapidly activating the transcription of a number of genes, and transcriptional increases in some azole-responsive genes can elevate azole resistance. The regulatory mechanisms that control transcriptional responses to azole stress in filamentous fungi are not well understood. This study identified a bZIP transcription factor, ADS-4 (antifungaldrugsensitive-4), as a new regulator of adaptive responses and resistance to antifungal azoles. Transcription ofads-4inNeurospora crassacells increased when they were subjected to ketoconazole treatment, whereas the deletion ofads-4resulted in hypersensitivity to ketoconazole and fluconazole. In contrast, the overexpression ofads-4increased resistance to fluconazole and ketoconazole inN. crassa. Transcriptome sequencing (RNA-seq) analysis, followed by quantitative reverse transcription (qRT)-PCR confirmation, showed that ADS-4 positively regulated the transcriptional responses of at least six genes to ketoconazole stress inN. crassa. The gene products of four ADS-4-regulated genes are known contributors to azole resistance, including the major efflux pump CDR4 (Pdr5p ortholog), an ABC multidrug transporter (NcAbcB), sterol C-22 desaturase (ERG5), and a lipid transporter (NcRTA2) that is involved in calcineurin-mediated azole resistance. Deletion of theads-4-homologous gene Afads-4inAspergillus fumigatuscaused hypersensitivity to itraconazole and ketoconazole, which suggested that ADS-4 is a functionally conserved regulator of adaptive responses to azoles. This study provides important information on a new azole resistance factor that could be targeted by a new range of antifungal pesticides and drugs.

scholarly journals Species Identification andIn VitroAntifungal Susceptibility ofAspergillus terreusSpecies Complex Clinical Isolates from a French Multicenter Study

2018 ◽  
Vol 62 (5) ◽  
pp. e02315-17 ◽  
Author(s):  
S. Imbert ◽  
A. C. Normand ◽  
S. Ranque ◽  
J. M. Costa ◽  
J. Guitard ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Antifungal Susceptibility ◽  
Sensu Stricto ◽  
Antifungal Drugs ◽  
Clinical Isolates ◽  
Clinical Samples ◽  
Azole Resistance ◽  
University Hospitals ◽  
Content Type ◽  
Interesting Alternative

ABSTRACTAspergillussectionTerreiis a species complex currently comprised of 14 cryptic species whose prevalence in clinical samples as well as antifungal susceptibility are poorly known. The aims of this study were to investigateA. Terreiclinical isolates at the species level and to perform antifungal susceptibility analyses by reference and commercial methods. Eighty-two clinicalA. Terreiisolates were collected from 8 French university hospitals. Molecular identification was performed by sequencing parts of beta-tubulin and calmodulin genes. MICs or minimum effective concentrations (MECs) were determined for 8 antifungal drugs using both EUCAST broth microdilution (BMD) methods and concentration gradient strips (CGS). Among the 79A. Terreiisolates,A. terreus stricto sensu(n= 61),A. citrinoterreus(n= 13),A. hortai(n= 3), andA. alabamensis(n= 2) were identified. All strains had MICs of ≥1 mg/liter for amphotericin B, except for two isolates (bothA. hortai) that had MICs of 0.25 mg/liter. FourA. terreusisolates were resistant to at least one azole drug, including one with pan-azole resistance, yet no mutation in theCYP51Agene was found. All strains had low MECs for the three echinocandins. The essential agreements (EAs) between BMD and CGS were >90%, except for those of amphotericin B (79.7%) and itraconazole (73.4%). Isolates belonging to theA. sectionTerreiidentified in clinical samples show wider species diversity beyond the knownA. terreus sensu stricto. Azole resistance inside the sectionTerreiis uncommon and is not related to CYP51A mutations here. Finally, CGS is an interesting alternative for routine antifungal susceptibility testing.

scholarly journals Genomewide Elucidation of Drug Resistance Mechanisms for Systemically Used Antifungal Drugs Amphotericin B, Caspofungin, and Voriconazole in the Budding Yeast

2019 ◽  
Vol 63 (9) ◽  
Author(s):  
Cigdem Balkan ◽  
Ilkcan Ercan ◽  
Esin Isik ◽  
Esra Sahin Akdeniz ◽  
Orhan Balcioglu ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Amphotericin B ◽  
Fungal Infections ◽  
Budding Yeast ◽  
Expression Patterns ◽  
Drug Susceptibility ◽  
Antifungal Drugs ◽  
Yeast Cells ◽  
Content Type ◽  
New Genes

ABSTRACT There are only a few antifungal drugs used systemically in treatment, and invasive fungal infections that are resistant to these drugs are an emerging problem in health care. In this study, we performed a high-copy-number genomic DNA (gDNA) library screening to find and characterize genes that reduce susceptibility to amphotericin B, caspofungin, and voriconazole in Saccharomyces cerevisiae. We identified the PDR16 and PMP3 genes for amphotericin B, the RMD9 and SWH1 genes for caspofungin, and the MRS3 and TRI1 genes for voriconazole. The deletion mutants for PDR16 and PMP3 were drug susceptible, but the other mutants had no apparent susceptibility. Quantitative-PCR analyses suggested that the corresponding drugs upregulated expression of the PDR16, PMP3, SWH1, and MRS3 genes. To further characterize these genes, we also profiled the global expression patterns of the cells after treatment with the antifungals and determined the genes and paths that were up- or downregulated. We also cloned Candida albicans homologs of the PDR16, PMP3, MRS3, and TRI1 genes and expressed them in S. cerevisiae. Heterologous expression of Candida homologs also provided reduced drug susceptibility to the budding yeast cells. Our analyses suggest the involvement of new genes in antifungal drug resistance.

scholarly journals Dectin-2-Targeted Antifungal Liposomes Exhibit Enhanced Efficacy

mSphere ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Suresh Ambati ◽  
Emma C. Ellis ◽  
Jianfeng Lin ◽  
Xiaorong Lin ◽  
Zachary A. Lewis ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Aspergillus Fumigatus ◽  
Effective Dose ◽  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Antifungal Drugs ◽  
Extracellular Matrices ◽  
Content Type ◽  
Order Of Magnitude ◽  
Life Threatening

ABSTRACT Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus cause life-threatening candidiasis, cryptococcosis, and aspergillosis, resulting in several hundred thousand deaths annually. The patients at the greatest risk of developing these life-threatening invasive fungal infections have weakened immune systems. The vulnerable population is increasing due to rising numbers of immunocompromised individuals as a result of HIV infection or immunosuppressed individuals receiving anticancer therapies and/or stem cell or organ transplants. While patients are treated with antifungals such as amphotericin B, all antifungals have serious limitations due to lack of sufficient fungicidal effect and/or host toxicity. Even with treatment, 1-year survival rates are low. We explored methods of increasing drug effectiveness by designing fungicide-loaded liposomes specifically targeted to fungal cells. Most pathogenic fungi are encased in cell walls and exopolysaccharide matrices rich in mannans. Dectin-2 is a mammalian innate immune membrane receptor that binds as a dimer to mannans and signals fungal infection. We coated amphotericin-loaded liposomes with monomers of Dectin-2’s mannan-binding domain, sDectin-2. sDectin monomers were free to float in the lipid membrane and form dimers that bind mannan substrates. sDectin-2-coated liposomes bound orders of magnitude more efficiently to the extracellular matrices of several developmental stages of C. albicans, C. neoformans, and A. fumigatus than untargeted control liposomes. Dectin-2-coated amphotericin B-loaded liposomes reduced the growth and viability of all three species more than an order of magnitude more efficiently than untargeted control liposomes and dramatically decreased the effective dose. Future efforts focus on examining pan-antifungal targeted liposomal drugs in animal models of fungal diseases. IMPORTANCE Invasive fungal diseases caused by Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus have mortality rates ranging from 10 to 95%. Individual patient costs may exceed $100,000 in the United States. All antifungals in current use have serious limitations due to host toxicity and/or insufficient fungal cell killing that results in recurrent infections. Few new antifungal drugs have been introduced in the last 2 decades. Hence, there is a critical need for improved antifungal therapeutics. By targeting antifungal-loaded liposomes to α-mannans in the extracellular matrices secreted by these fungi, we dramatically reduced the effective dose of drug. Dectin-2-coated liposomes loaded with amphotericin B bound 50- to 150-fold more strongly to C. albicans, C. neoformans, and A. fumigatus than untargeted liposomes and killed these fungi more than an order of magnitude more efficiently. Targeting drug-loaded liposomes specifically to fungal cells has the potential to greatly enhance the efficacy of most antifungal drugs.

scholarly journals Trends in Antifungal Drug Susceptibility of Cryptococcus neoformans Isolates Obtained through Population-Based Surveillance in South Africa in 2002-2003 and 2007-2008

2011 ◽  
Vol 55 (6) ◽  
pp. 2606-2611 ◽  
Author(s):  
Nelesh P. Govender ◽  
Jaymati Patel ◽  
Marelize van Wyk ◽  
Tom M. Chiller ◽  
Shawn R. Lockhart ◽  
...  
Keyword(s):  
South Africa ◽  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Fungal Infections ◽  
Antifungal Susceptibility ◽  
Drug Susceptibility ◽  
Population Based ◽  
Content Type ◽  
Microdilution Method ◽  
Broth Microdilution Method

ABSTRACTCryptococcus neoformansis the most common cause of meningitis among adult South Africans with HIV infection/AIDS. Widespread use of fluconazole for treatment of cryptococcal meningitis and other HIV-associated opportunistic fungal infections in South Africa may lead to the emergence of isolates with reduced fluconazole susceptibility. MIC testing using a reference broth microdilution method was used to determine if isolates with reduced susceptibility to fluconazole or amphotericin B had emerged among cases of incident disease. Incident isolates were tested from two surveillance periods (2002-2003 and 2007-2008) when population-based surveillance was conducted in Gauteng Province, South Africa. These isolates were also tested for susceptibility to flucytosine, itraconazole, voriconazole, and posaconazole. Serially collected isolate pairs from cases at several large South African hospitals were also tested for susceptibility to fluconazole. Of the 487 incident isolates tested, only 3 (0.6%) demonstrated a fluconazole MIC of ≥16 μg/ml; all of these isolates were from 2002-2003. All incident isolates were inhibited by very low concentrations of amphotericin B and exhibited very low MICs to voriconazole and posaconazole. Of 67 cases with serially collected isolate pairs, only 1 case was detected where the isolate collected more than 30 days later had a fluconazole MIC value significantly higher than the MIC of the corresponding incident isolate. Although routine antifungal susceptibility testing of incident isolates is not currently recommended in clinical settings, it is still clearly important for public health to periodically monitor for the emergence of resistance.

scholarly journals In VitroActivities of Nine Antifungal Drugs against 81 Phialophora and Cyphellophora Isolates

2012 ◽  
Vol 56 (11) ◽  
pp. 6044-6047 ◽  
Author(s):  
Peiying Feng ◽  
M. Javad Najafzadeh ◽  
Jiufeng Sun ◽  
Sarah Ahmed ◽  
Liyan Xi ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Antifungal Drugs ◽  
Content Type

ABSTRACTCyphellophora guyanensis(n= 15), otherCyphellophoraspecies (n= 11),Phialophora europaea(n= 43), and otherPhialophoraspecies (n= 12) were testedin vitroagainst nine antifungal drugs. The MIC90s across all of the strains (n= 81) were, in increasing order, as follows: posaconazole, 0.063 μg/ml; itraconazole, 0.5 μg/ml; voriconazole, 1 μg/ml; micafungin, 1 μg/ml; terbinafine, 2 μg/ml; isavuconazole, 4 μg/ml; caspofungin, 4 μg/ml; fluconazole, 8 μg/ml; amphotericin B, 16 μg/ml.

scholarly journals Reversal of Azole Resistance inCandida albicansby Sulfa Antibacterial Drugs

2017 ◽  
Vol 62 (3) ◽  
Author(s):  
Hassan E. Eldesouky ◽  
Abdelrahman Mayhoub ◽  
Tony R. Hazbun ◽  
Mohamed N. Seleem
Keyword(s):  
Treatment Options ◽  
Antifungal Drugs ◽  
Infection Model ◽  
Azole Resistance ◽  
Global Public Health ◽  
Sulfa Drugs ◽  
Antibacterial Drugs ◽  
Content Type

ABSTRACTInvasive candidiasis presents an emerging global public health challenge due to the emergence of resistance to the frontline treatment options, such as fluconazole. Hence, the identification of other compounds capable of pairing with fluconazole and averting azole resistance would potentially prolong the clinical utility of this important group. In an effort to repurpose drugs in the field of antifungal drug discovery, we explored sulfa antibacterial drugs for the purpose of reversing azole resistance inCandida. In this study, we assembled and investigated a library of 21 sulfa antibacterial drugs for their ability to restore fluconazole sensitivity inCandida albicans. Surprisingly, the majority of assayed sulfa drugs (15 of 21) were found to exhibit synergistic relationships with fluconazole by checkerboard assay with fractional inhibitory concentration index (ΣFIC) values ranging from <0.0312 to 0.25. Remarkably, five sulfa drugs were able to reverse azole resistance in a clinically achievable range. The structure-activity relationships (SARs) of the amino benzene sulfonamide scaffold as antifungal agents were studied. We also identified the possible mechanism of the synergistic interaction of sulfa antibacterial drugs with azole antifungal drugs. Furthermore, the ability of sulfa antibacterial drugs to inhibitCandidabiofilm by 40%in vitrowas confirmed. In addition, the effects of sulfa-fluconazole combinations onCandidagrowth kinetics and efflux machinery were explored. Finally, using aCaenorhabditis elegansinfection model, we demonstrated that the sulfa-fluconazole combination does possess potent antifungal activityin vivo, reducingCandidain infected worms by ∼50% compared to the control.

scholarly journals Acylhydrazones as Antifungal Agents Targeting the Synthesis of Fungal Sphingolipids

2018 ◽  
Vol 62 (5) ◽  
Author(s):  
Cristina Lazzarini ◽  
Krupanandan Haranahalli ◽  
Robert Rieger ◽  
Hari Krishna Ananthula ◽  
Pankaj B. Desai ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Antifungal Agents ◽  
Fungal Infections ◽  
Antifungal Drugs ◽  
Fungal Resistance ◽  
Content Type ◽  
Highly Active ◽  
Pharmacokinetic Properties ◽  
Pass Through

ABSTRACTThe incidence of invasive fungal infections has risen dramatically in recent decades. Current antifungal drugs are either toxic, likely to interact with other drugs, have a narrow spectrum of activity, or induce fungal resistance. Hence, there is a great need for new antifungals, possibly with novel mechanisms of action. Previously our group reported an acylhydrazone called BHBM that targeted the sphingolipid pathway and showed strong antifungal activity against several fungi. In this study, we screened 19 derivatives of BHBM. Three out of 19 derivatives were highly active againstCryptococcus neoformansin vitroand had low toxicity in mammalian cells. In particular, one of them, called D13, had a high selectivity index and showed better activity in an animal model of cryptococcosis, candidiasis, and pulmonary aspergillosis. D13 also displayed suitable pharmacokinetic properties and was able to pass through the blood-brain barrier. These results suggest that acylhydrazones are promising molecules for the research and development of new antifungal agents.

scholarly journals Lactoferrin Is Broadly Active against Yeasts and Highly Synergistic with Amphotericin B

2020 ◽  
Vol 64 (5) ◽  
Author(s):  
Kenya E. Fernandes ◽  
Kerry Weeks ◽  
Dee A. Carter
Keyword(s):  
Amphotericin B ◽  
Galleria Mellonella ◽  
Comprehensive Evaluation ◽  
Yeast Species ◽  
Phenotypic Diversity ◽  
Antifungal Drugs ◽  
Fungal Cell ◽  
Content Type ◽  
Iron Saturation ◽  
Capsule Size

ABSTRACT Lactoferrin (LF) is a multifunctional milk protein with antimicrobial activity against a range of pathogens. While numerous studies report that LF is active against fungi, there are considerable differences in the level of antifungal activity and the capacity of LF to interact with other drugs. Here we undertook a comprehensive evaluation of the antifungal spectrum of activity of three defined sources of LF across 22 yeast and 24 mold species and assessed its interactions with six widely used antifungal drugs. LF was broadly and consistently active against all yeast species tested (MICs, 8 to 64 μg/ml), with the extent of activity being strongly affected by iron saturation. LF was synergistic with amphotericin B (AMB) against 19 out of 22 yeast species tested, and synergy was unaffected by iron saturation but was affected by the extent of LF digestion. LF-AMB combination therapy significantly prolonged the survival of Galleria mellonella wax moth larvae infected with Candida albicans or Cryptococcus neoformans and decreased the fungal burden 12- to 25-fold. Evidence that LF directly interacts with the fungal cell surface was seen via scanning electron microscopy, which showed pore formation, hyphal thinning, and major cell collapse in response to LF-AMB synergy. Important virulence mechanisms were disrupted by LF-AMB treatment, which significantly prevented biofilms in C. albicans and C. glabrata, inhibited hyphal development in C. albicans, and reduced cell and capsule size and phenotypic diversity in Cryptococcus. Our results demonstrate the potential of LF-AMB as an antifungal treatment that is broadly synergistic against important yeast pathogens, with the synergy being attributed to the presence of one or more LF peptides.

scholarly journals Whole-Genome Approach to Understanding the Mechanism of Action of a Histatin 5-Derived Peptide

2019 ◽  
Vol 64 (3) ◽  
Author(s):  
Cody B. Bullock ◽  
David S. McNabb ◽  
Inés Pinto
Keyword(s):  
Mechanism Of Action ◽  
Fungal Infections ◽  
Antifungal Drugs ◽  
Content Type ◽  
Histatin 5 ◽  
Amino Acid Peptide ◽  
Killing Activity ◽  
Transport Chain ◽  
Mitochondrial Functions ◽  
Increased Sensitivity

ABSTRACT The incidence of opportunistic fungal infections that threaten immunocompromised patients, along with the limited arsenal of antifungal drugs, calls for renewed efforts to develop novel antifungal therapies. Antimicrobial peptides have garnered interest as potential therapeutics. Among naturally occurring peptides, histatin 5 is a well-characterized 24-amino-acid peptide with strong antifungal activity. Our lab has identified a smaller histatin derivative, KM29, with stronger activity against multiple Candida spp., prompting us to investigate its fungicidal mechanism. A genetic screen was developed to test the Saccharomyces cerevisiae genomewide deletion collection for mutants with increased or decreased peptide sensitivity. The goal was to identify genes that would reveal insights into the mechanism of action of KM29, to be assessed in Candida albicans. Several biological processes yielded increased sensitivity, with endosomal transport and vacuolar function appearing at high frequencies. Among the pathways involved in increased resistance, mitochondrial function showed the highest normalized genome frequency; hence, we focused on characterizing this pathway. KM29 localizes to mitochondria, and the killing activity depends on a functional electron transport chain. In addition, KM29 triggered reactive oxygen species (ROS) production, which was responsible for some cell death but insufficient to account for the complete killing activity. In agreement with this finding, we found that KM29 induced mitochondrial fragmentation and a mild loss of mitochondrial membrane potential. Furthermore, respiratory mutants exhibited severely diminished KM29 uptake. We confirmed this behavior in a C. albicans respiratory mutant. Taking our findings together, this work delineates the mitochondrial functions associated with KM29 fungicidal activity and provides additional pathways for further characterization in Candida spp.

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