scholarly journals A Screening Assay Based on Host-Pathogen Interaction Models Identifies a Set of Novel Antifungal Benzimidazole Derivatives

2011 ◽  
Vol 55 (10) ◽  
pp. 4789-4801 ◽  
Author(s):  
Anke Burger-Kentischer ◽  
Doris Finkelmeier ◽  
Petra Keller ◽  
Jörg Bauer ◽  
Holger Eickhoff ◽  
...  

ABSTRACTFungal infections are a serious health problem in clinics, especially in the immune-compromised patient. Disease ranges from widespread superficial infections like vulvovaginal infections to life-threatening systemic candidiasis. Especially for systemic mycoses, only a limited arsenal of antifungals is available. The most commonly used classes of antifungal compounds used include azoles, polyenes, and echinocandins. Due to emerging resistance to standard therapy, significant side effects, and high costs for several antifungals, there is a medical need for new antifungals in the clinic and general practice. In order to expand the arsenal of compounds with antifungal activities, we screened a compound library including more than 35,000 individual compounds derived from organic synthesis as well as combinatorial compound collections representing mixtures of compounds for antimycotic activity. In total, more than 100,000 compounds were screened using a new type of activity-selectivity assay, analyzing both the antifungal activity and the compatibility with human cells at the same time. One promising hit, an (S)-2-aminoalkyl benzimidazole derivative, was developed among a series of lead compounds showing potent antifungal activity. (S)-2-(1-Aminoisobutyl)-1-(3-chlorobenzyl) benzimidazole showed the highest antifungal activity and the best compatibility with human cells in several cell culture models and against a number of clinical isolates of several species of pathogenicCandidayeasts. Transcriptional profiling indicates that the newly discovered compound is a potential inhibitor of the ergosterol pathway, in contrast to other benzimidazole derivatives, which target microtubules.

2015 ◽  
Vol 59 (10) ◽  
pp. 6296-6307 ◽  
Author(s):  
Petra Keller ◽  
Christoph Müller ◽  
Isabel Engelhardt ◽  
Ekkehard Hiller ◽  
Karin Lemuth ◽  
...  

ABSTRACTFungal infections are a leading cause of morbidity and death for hospitalized patients, mainly because they remain difficult to diagnose and to treat. Diseases range from widespread superficial infections such as vulvovaginal infections to life-threatening systemic candidiasis. For systemic mycoses, only a restricted arsenal of antifungal agents is available. Commonly used classes of antifungal compounds include azoles, polyenes, and echinocandins. Due to emerging resistance to standard therapies, significant side effects, and high costs for several antifungals, there is a need for new antifungals in the clinic. In order to expand the arsenal of compounds with antifungal activity, we previously screened a compound library using a cell-based screening assay. A set of novel benzimidazole derivatives, including (S)-2-(1-aminoisobutyl)-1-(3-chlorobenzyl)benzimidazole (EMC120B12), showed high antifungal activity against several species of pathogenic yeasts, includingCandida glabrataandCandida krusei(species that are highly resistant to antifungals). In this study, comparative analysis of EMC120B12 versus fluconazole and nocodazole, using transcriptional profiling and sterol analysis, strongly suggested that EMC120B12 targets Erg11p in the ergosterol biosynthesis pathway and not microtubules, like other benzimidazoles. In addition to the marker sterol 14-methylergosta-8,24(28)-dien-3β,6α-diol, indicating Erg11p inhibition, related sterols that were hitherto unknown accumulated in the cells during EMC120B12 treatment. The novel sterols have a 3β,6α-diol structure. In addition to the identification of novel sterols, this is the first time that a benzimidazole structure has been shown to result in a block of the ergosterol pathway.


2018 ◽  
Vol 15 (2) ◽  
pp. 154-159
Author(s):  
Asaf Evrim Evren ◽  
Sinem Tekinkoca ◽  
Leyla Yurttas

Background: Due to multi-drug, extended-drug, and pandrug resistance phenotypes, bacterial resistance to antibiotics and fungal infections are a general health issue. Particulary, increase of fungal infections due to secondary cause of human diseases have been observed. An extensive variety of benzimidazole derivatives have been characterized for their chemotherapeutic significance. Benzimidazole derivatives have received important attention because of pharmacological significance during current years, especially antimicrobial, anti-fungal, antitubercular, antioxidant, anti-Alzheimer's disease and antihypertension activities. Methods: Some N-(1H-benzimidazol-2-yl)-2-mercaptoacetamide derivatives (2a-h) were synthesised and evaluated for their antimicrobial activity. The title compounds were gained by reacting N-(1H-benzimidazol-2-yl)-2-chloroacetamide with some substituted 2-mercapto heterocyclic rings. The synthesised compounds were investigated for their antimicrobial activities against C. albicans (ATCC 24433), C. krusei (ATCC 6258), C. glabrata (ATCC90030), C. parapsilosis (ATCC 22019), E. coli (ATCC 25922), E. coli (ATCC 35218), E. feacalis (ATCC 51299), E. feacalis (ATCC 29212), S. aureus (ATCC 25923), K. pneumoniae (ATCC 700603), P. aeruginosa (ATCC 27853). Results: The compounds showed high antifungal activity when compared with standard drug ketoconazole. In addition, all compounds (MIC 100 µg/mL) showed inhibitor activity against P. aeruginosa at two fold concentration of chloramphenicol (MIC 50 µg/mL). Also, compounds 2a, 2c and 2e (MIC: 50 µg/mL) have equal effect against E. coli (ATCC 35218) and more effective than other compounds (MIC of chloramphenicol: 100 µg/mL). Conclusıon: All compounds showed notable activity. Compounds have determined to possess higher antifungal activity than antibacterial activity. Additionally, compounds 2a with 1-methyltetrazole, 2c with benzothiazole and 2e with 6-chlorobenzothiazole moieties were found as the most active compounds.


2019 ◽  
Vol 85 (9) ◽  
Author(s):  
Xiaodan Li ◽  
Yikui Li ◽  
Ren Wang ◽  
Qizhi Wang ◽  
Ling Lu

ABSTRACTFungal infections not only cause extensive agricultural damage but also result in serious diseases in the immunodeficient populations of human beings. Moreover, the increasing emergence of drug resistance has led to a decrease in the efficacy of current antifungals. Thus, screening of new antifungal agents is imperative in the fight against antifungal drug resistance. In this study, we show that an endophytic bacterium,Burkholderia gladioliHDXY-02, isolated from the medicinal plantLycoris aurea, showed broad-spectrum antifungal activity against plant and human fungal pathogens. An antifungal ability assay indicated that the bioactive component was produced from strain HDXY-02 having an extracellular secreted component with a molecular weight lower than 1,000 Da. In addition, we found that this new antifungal could be produced effectively by liquid fermentation of HDXY-02. Furthermore, the purified component contributing to the antifungal activity was identified to be toxoflavin, a yellow compound possessing a pyrimido[5,4-e][1,2,4]triazine ring.In vitrobioactivity studies demonstrated that purified toxoflavin fromB. gladioliHDXY-02 cultures had a significant antifungal activity against the human fungal pathogenAspergillus fumigatus, resulting in abolished germination of conidia. More importantly, the growth inhibition by toxoflavin was observed in both wild-type and drug-resistant mutants (cyp51Aand non-cyp51A) ofA. fumigatus. Finally, an optimized protocol for the large-scale production of toxoflavin (1,533 mg/liter) has been developed. Taken together, our findings provide a promising biosynthetic resource for producing a new antifungal reagent, toxoflavin, from isolates of the endophytic bacteriumB. gladioli.IMPORTANCEHuman fungal infections are a growing problem associated with increased morbidity and mortality. Moreover, a growing number of antifungal-resistant fungal isolates have been reported over the past decade. Thus, the need for novel antifungal agents is imperative. In this study, we show that an endophytic bacterium,Burkholderia gladioli, isolated from the medicinal plantLycoris aurea, is able to abundantly secrete a compound, toxoflavin, which has a strong fungicidal activity not only against plant fungal pathogens but also against human fungal pathogensAspergillus fumigatusandCandida albicans,Cryptococcus neoformans, and the model filamentous fungusAspergillus nidulans. More importantly, toxoflavin also displays an efficacious inhibitory effect against azole antifungal-resistant mutants ofA. fumigatus. Consequently, our findings provide a promising approach to abundantly produce toxoflavin, which has novel broad-spectrum antifungal activity, especially against those currently problematic drug-resistant isolates.


2017 ◽  
Vol 61 (7) ◽  
Author(s):  
Tatiana Y. Hargrove ◽  
Edward P. Garvey ◽  
William J. Hoekstra ◽  
Christopher M. Yates ◽  
Zdzislaw Wawrzak ◽  
...  

ABSTRACT Within the past few decades, the incidence and complexity of human fungal infections have increased, and therefore, the need for safer and more efficient, broad-spectrum antifungal agents is high. In the study described here, we characterized the new tetrazole-based drug candidate VT-1598 as an inhibitor of sterol 14α-demethylase (CYP51B) from the filamentous fungus Aspergillus fumigatus. VT-1598 displayed a high affinity of binding to the enzyme in solution (dissociation constant, 13 ± 1 nM) and in the reconstituted enzymatic reaction was revealed to have an inhibitory potency stronger than the potencies of all other simultaneously tested antifungal drugs, including fluconazole, voriconazole, ketoconazole, and posaconazole. The X-ray structure of the VT-1598/A. fumigatus CYP51 complex was determined and depicts the distinctive binding mode of the inhibitor in the enzyme active site, suggesting the molecular basis of the improved drug potency and broad-spectrum antifungal activity. These data show the formation of an optimized hydrogen bond between the phenoxymethyl oxygen of VT-1598 and the imidazole ring nitrogen of His374, the CYP51 residue that is highly conserved across fungal pathogens and fungus specific. Comparative structural analysis of A. fumigatus CYP51/voriconazole and Candida albicans CYP51/VT-1161 complexes supports the role of H bonding in fungal CYP51/inhibitor complexes and emphasizes the importance of an optimal distance between this interaction and the inhibitor-heme iron interaction. Cellular experiments using two A. fumigatus strains (strains 32820 and 1022) displayed a direct correlation between the effects of the drugs on CYP51B activity and fungal growth inhibition, indicating the noteworthy anti-A. fumigatus potency of VT-1598 and confirming its promise as a broad-spectrum antifungal agent.


2016 ◽  
Vol 60 (6) ◽  
pp. 3551-3557 ◽  
Author(s):  
Anderson Ramos da Silva ◽  
João Batista de Andrade Neto ◽  
Cecília Rocha da Silva ◽  
Rosana de Sousa Campos ◽  
Rose Anny Costa Silva ◽  
...  

The incidence of fungal infections and, in particular, the incidence of fungal antibiotic resistance, which is associated with biofilm formation, have significantly increased, contributing to morbidity and mortality. Thus, new therapeutic strategies need to be developed. In this context, natural products have emerged as a major source of possible antifungal agents. Berberine is a protoberberine-type isoquinoline alkaloid isolated from the roots, rhizomes, and stem bark of natural herbs, such asBerberis aquifolium,Berberis vulgaris,Berberis aristata, andHydrastis canadensis, and ofPhellodendron amurense. Berberine has been proven to have broad antibacterial and antifungal activity. In the present study, the potential antifungal effect of berberine against fluconazole-resistantCandidaandCryptococcus neoformansstrains, as well as against the biofilm form ofCandidaspp., was assessed. The antifungal effect of berberine was determined by a broth microdilution method (the M27-A3 method of the Clinical and Laboratory Standards Institute) and flow cytometry techniques, in which the probable mechanism of action of the compound was also assessed. For biofilm assessment, a colorimetric 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to determine the susceptibility of sessile cells. The isolates used in the study belonged to the Laboratory of Bioprospection and Experiments in Yeast (LABEL) of the Federal University of Ceará. After 24 and 72 h, fluconazole-resistantCandidaandCryptococcus neoformansstrains showed berberine MICs equal to 8 μg/ml and 16 μg/ml, respectively. Cytometric analysis showed that treatment with berberine caused alterations to the integrity of the plasma and mitochondrial membranes and DNA damage, which led to cell death, probably by apoptosis. Assessment of biofilm-forming isolates after treatment showed statistically significant reductions in biofilm cell activity (P< 0.001).


2018 ◽  
Vol 62 (10) ◽  
Author(s):  
Yanan Zhao ◽  
Min Hee Lee ◽  
Padmaja Paderu ◽  
Annie Lee ◽  
Cristina Jimenez-Ortigosa ◽  
...  

ABSTRACT APX001 is a first-in-class, intravenous and orally available, broad-spectrum antifungal agent in clinical development for the treatment of life-threatening invasive fungal infections. The half-life of APX001A, the active moiety of APX001, is significantly shorter in mice than in humans (1.4 to 2.75 h in mice versus 2 to 2.5 days in humans), making the exploration of efficacy in mouse models difficult. After pretreatment with 1-aminobenzotriazole (ABT), a nonspecific cytochrome P450 inhibitor, greatly increased plasma APX001A exposure was observed in mice of different strains and of both genders. As a consequence, 26 mg/kg APX001 plus ABT sterilized kidneys in mice infected with Candida albicans, while APX001 alone at the same dose resulted in a modest burden reduction of only 0.2 log10 CFU/g, relative to the vehicle control. In the presence of ABT, 2 days of once-daily dosing with APX001 at 26 mg/kg also demonstrated significant in vivo efficacy in the treatment of Candida glabrata infections in mice. Potent kidney burden reduction was achieved in mice infected with susceptible, echinocandin-resistant, or multidrug-resistant strains. In contrast, the standard of care (micafungin) was ineffective in treating infections caused by the resistant C. glabrata isolates.


2020 ◽  
Vol 64 (3) ◽  
Author(s):  
Marhiah C. Montoya ◽  
Sarah Beattie ◽  
Kathryn M. Alden ◽  
Damian J. Krysan

ABSTRACT The antifungal pharmacopeia is critically small, particularly in light of the recent emergence of multidrug-resistant pathogens, such as Candida auris. Here, we report that derivatives of the antimalarial drug mefloquine have broad-spectrum antifungal activity against pathogenic yeasts and molds. In addition, the mefloquine derivatives have activity against clinical isolates that are resistant to one or more of the three classes of antifungal drugs currently used to treat invasive fungal infections, indicating that they have a novel mechanism of action. Importantly, the in vitro toxicity profiles obtained using human cell lines indicated that the toxicity profiles of the mefloquine derivatives are very similar to those of the parent mefloquine, despite being up to 64-fold more active against fungal cells. In addition to direct antifungal activity, subinhibitory concentrations of the mefloquine derivatives inhibited the expression of virulence traits, including filamentation in Candida albicans and capsule formation/melanization in Cryptococcus neoformans. Mode/mechanism-of-action experiments indicated that the mefloquine derivatives interfere with both mitochondrial and vacuolar function as part of a multitarget mechanism of action. The broad-spectrum scope of activity, blood-brain barrier penetration, and large number of previously synthesized analogs available combine to support the further optimization and development of the antifungal activity of this general class of drug-like molecules.


2018 ◽  
Vol 48 (2) ◽  
pp. 125-129
Author(s):  
K. ZOMORODIAN ◽  
S. KHABNADIDEH ◽  
L. ZAMANI ◽  
K. PAKSHIR ◽  
M. TAJADDOD

The extensive use of antifungal drugs and their resistance against fungal infections have led to discover new antimicrobial compounds. We previously described synthesis of some new derivatives of 2-methylbenzimidazole (1a-5a) and 5,6dimethylbenzimidazol (1b-5b). Here we evaluated the antimicrobial activities of these compounds against different species of micro organisms including gram positive and gram negative bacteria as well as fungi. Broth micro-dilution method as recommended by clinical and laboratory standard institute (CLSI) was used for this purpose. The results show compounds 2-Methyl-1-(3-methylbenzyl)-1H-benzo [d]imidazole (5a) and 5,6-Dimethyl-1-(3-methyl benzyl)-1H-benzo[d]imidazole (5b) had the best antifungal activity against the examined fungi and gram positive bacteria. Moreover these two compounds inhibited the growth of azole resistant strains. By comparison the relationship between the structures and activities of the tested compounds revealed that the presence of methyl residue in meta position of benzyl group enhance the antifungal activity. Regarding a broad spectrum antifungal activities of some of the tested compounds, they might be a good candidate for further in vivo studies to evaluate their pharmacological activity and toxicity as a novel antifungal agents.


2016 ◽  
pp. AAC.01959-16 ◽  
Author(s):  
Tanvi Shekhar-Guturja ◽  
Walters Aji Tebung ◽  
Harley Mount ◽  
Ningning Liu ◽  
Julia R. Köhler ◽  
...  

Invasive fungal infections are a leading cause of human mortality. Effective treatment is hindered by the rapid emergence of resistance to the limited number of antifungal drugs, demanding new strategies to treat life-threatening fungal infections. Here, we explore a powerful strategy to enhance antifungal efficacy using the natural product beauvericin against leading human fungal pathogens. We found that beauvericin potentiates the activity of azole antifungals against azole-resistantCandidaisolates via inhibition of multidrug efflux, and that beauvericin itself is effluxed via Yor1. As observed inSaccharomyces cerevisiae, we determined that beauvericin inhibits TOR signaling inCandida albicans. To further characterize beauvericin activity inC. albicans, we leveraged genome sequencing of beauvericin-resistant mutants. Resistance was conferred by mutations in transcription factor genesTAC1,which is a key regulator of multidrug efflux, andZCF29, which was uncharacterized. Transcriptional profiling and chromatin immunoprecipitation coupled to microarray analyses revealed that Zcf29 binds to and regulates the expression of multidrug transporter genes. Beyond drug resistance, we also discovered that beauvericin blocks theC. albicansmorphogenetic transition from yeast to filamentous growth in response to diverse cues. We found that beauvericin represses the expression of many filament-specific genes, including the transcription factorBRG1. Thus, we illuminate novel circuitry regulating multidrug efflux, and establish that simultaneously targeting drug resistance and morphogenesis provides a promising strategy to combat life-threatening fungal infections.


2015 ◽  
Vol 59 (8) ◽  
pp. 4584-4592 ◽  
Author(s):  
Julien Chaillot ◽  
Faiza Tebbji ◽  
Adnane Remmal ◽  
Charlie Boone ◽  
Grant W. Brown ◽  
...  

ABSTRACTThe monoterpene carvacrol, the major component of oregano and thyme oils, is known to exert potent antifungal activity against the pathogenic yeastCandida albicans. This monoterpene has been the subject of a considerable number of investigations that uncovered extensive pharmacological properties, including antifungal and antibacterial effects. However, its mechanism of action remains elusive. Here, we used integrative chemogenomic approaches, including genome-scale chemical-genetic and transcriptional profiling, to uncover the mechanism of action of carvacrol associated with its antifungal property. Our results clearly demonstrated that fungal cells require the unfolded protein response (UPR) signaling pathway to resist carvacrol. The mutants most sensitive to carvacrol in our genome-wide competitive fitness assay in the yeastSaccharomyces cerevisiaeexpressed mutations of the transcription factor Hac1 and the endonuclease Ire1, which is required for Hac1 activation by removing a nonconventional intron from the 3′ region ofHAC1mRNA. Confocal fluorescence live-cell imaging revealed that carvacrol affects the morphology and the integrity of the endoplasmic reticulum (ER). Transcriptional profiling of pathogenic yeastC. albicanscells treated with carvacrol demonstrated a bona fide UPR transcriptional signature. Ire1 activity detected by the splicing ofHAC1mRNA inC. albicanswas activated by carvacrol. Furthermore, carvacrol was found to potentiate antifungal activity of the echinocandin antifungal caspofungin and UPR inducers dithiothreitol and tunicamycin againstC. albicans. This comprehensive chemogenomic investigation demonstrated that carvacrol exerts its antifungal activity by altering ER integrity, leading to ER stress and the activation of the UPR to restore protein-folding homeostasis.


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