Repurposing an inhibitor of ribosomal biogenesis with broad anti-fungal activity

Retinoic acid mitigates the NSC319726-induced spermatogenesis dysfunction through cuproptosis-independent mechanisms

Copper ionophore NSC319726 has attracted researchers' attention in treating diseases, particularly cancers. However, its potential effects on male reproduction during medication are unclear. This study aimed to determine whether NSC319726 exposure affected the male reproductive system. The reproductive toxicity of NSC319726 was evaluated in male mice following a continuous exposure period of 5 weeks. The result showed that NSC319726 exposure caused testis index reduction, spermatogenesis dysfunction, and architectural damage in the testis and epididymis. The exposure interfered with spermatogonia proliferation, meiosis initiation, sperm count, and sperm morphology. The exposure also disturbed androgen synthesis and blood testis barrier integrity. NSC319726 treatment could elevate the copper ions in the testis to induce cuproptosis in the testis. Copper chelator rescued the elevated copper ions in the testis and partly restored the spermatogenesis dysfunction caused by NSC319726. NSC319726 treatment also decreased the level of retinol dehydrogenase 10 (RDH10), thereby inhibiting the conversion of retinol to retinoic acid, causing the inability to initiate meiosis. Retinoic acid treatment could rescue the meiotic initiation and spermatogenesis while not affecting the intracellular copper ion levels. The study provided an insight into the bio-safety of NSC319726. Retinoic acid could be a potential therapy for spermatogenesis impairment in patients undergoing treatment with NSC319726.

A novel zinc-chelating compound has antifungal activity against a wide range of Candida species, including multidrug-resistant Candida auris

Objectives

In recent years, the incidence of invasive fungal infections has increased, resulting in considerable morbidity and mortality, particularly among immunocompromised individuals. Potential challenges in treating these infections with the few existing antifungal agents highlight the urgency of developing new ones. Here, we evaluated six alkyl polyamine compounds (APCs), not previously reported as antifungal drugs to our knowledge, that could deprive fungi of essential transition metals.

Methods

The APC with confirmed antifungal activity against Candida spp. was analysed by using transcriptomics, followed by metal-addition experiments, mass spectrometric analyses and intracellular zinc quantification with a fluorescent probe.

Results

A cyclic APC with three pyridylmethyl groups, APC6, had high antifungal activity against a wide range of Candida species, including MDR Candida auris. We conclusively demonstrated that APC6 was able to capture zinc within fungal cells. APC6 not only exhibited activity against C. auris as a single agent but also enhanced the efficacy of an azole antifungal agent, voriconazole, in vitro and in vivo. APC6 disrupted the biofilms formed by Candida species.

Conclusions

This zinc-chelating compound has potential as an antifungal agent, and the control of zinc levels in Candida species could be a powerful approach to treating drug-resistant candidiasis.

The Virtuous Galleria mellonella Model for Scientific Experimentation

The first research on the insect Galleria mellonella was published 85 years ago, and the larva is now widely used as a model to study infections caused by bacterial and fungal pathogens, for screening new antimicrobials, to study the adjacent immune response in co-infections or in host-pathogen interaction, as well as in a toxicity model. The immune system of the G. mellonella model shows remarkable similarities with mammals. Furthermore, results from G. mellonella correlate positively with mammalian models and with other invertebrate models. Unlike other invertebrate models, G. mellonella can withstand temperatures of 37 °C, and its handling and experimental procedures are simpler. Despite having some disadvantages, G. mellonella is a virtuous in vivo model to be used in preclinical studies, as an intermediate model between in vitro and mammalian in vivo studies, and is a great example on how to apply the bioethics principle of the 3Rs (Replacement, Reduction, and Refinement) in animal experimentation. This review aims to discuss the progress of the G. mellonella model, highlighting the key aspects of its use, including experimental design considerations and the necessity to standardize them. A different score in the “cocoon” category included in the G. mellonella Health Index Scoring System is also proposed.

Proteomic Response of Paracoccidioides brasiliensis Exposed to the Antifungal 4-Methoxynaphthalene-N-acylhydrazone Reveals Alteration in Metabolism

Background: Paracoccidioidomycosis is a neglected mycosis with a high socioeconomic impact that requires long-term treatment with antifungals that have limitations in their use. The development of antifungals targeting essential proteins that are present exclusively in the fungus points to a potentially promising treatment. Methods: The inhibitor of the enzyme homoserine dehydrogenase drove the synthesis of N'-(2-hydroxybenzylidene)-4-methoxy-1-naphthohydrazide (AOS). This compound was evaluated for its antifungal activity in different species of Paracoccidioides and the consequent alteration in the proteomic profile of Paracoccidioides brasiliensis. Results: The compound showed a minimal inhibitory concentration ranging from 0.75 to 6.9 μM with a fungicidal effect on Paracoccidioides spp. and high selectivity index. AOS differentially regulated proteins related to glycolysis, TCA, the glyoxylate cycle, the urea cycle and amino acid metabolism, including homoserine dehydrogenase. In addition, P. brasiliensis inhibited protein synthesis and stimulated reactive oxygen species in the presence of AOS. Conclusions: AOS is a promising antifungal agent for the treatment of PCM, targeting important metabolic processes of the fungus.

Small RNAs target native and cross-kingdom transcripts on both sides of the wheat stripe rust interaction

The wheat stripe rust fungus (Puccinia striiformis f.sp. tritici) threatens global wheat production. Small RNAs (sRNAs) modulate plant defense induction, and RNA exchange between host and microbe causes cross-kingdom gene silencing, but few examples are known in rust fungi. This study combined sRNA, parallel analysis of RNA ends, and gene expression data to discover sRNA-target pairs on each side of the interaction. Specific wheat 24 nt sRNAs were suppressed, while particular 35 nt fragments were strongly induced upon infection. Wheat sRNAs cleaved fungal transcripts coding for a ribosomal protein and a glycosyl hydrolase effector. Fungal microRNA-like and phased 21 nt sRNAs originated from long inverted repeats near protein coding genes. Fungal sRNAs targeted native transcripts: transposons and kinases; and cross-kingdom transcripts: a wheat nucleotide-binding domain leucine-rich repeat receptor (NLR) and multiple defense-related transcription factor families. This work sheds light on host-microbe coevolution and delivers prospects for developing pathogen control biotechnology.

Exposure of Candida parapsilosis to the silver(I) compound SBC3 induces alterations in the proteome and reduced virulence

The antimicrobial properties of silver have been exploited for many centuries and continue to gain interest in the fight against antimicrobial drug resistance. The broad-spectrum activity and low toxicity of silver have led to its incorporation into a wide range of novel antimicrobial agents, including N-heterocyclic carbene (NHC) complexes. The antimicrobial activity and in vivo efficacy of the NHC silver(I) acetate complex SBC3, derived from 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene (NHC*), have previously been demonstrated, although the mode(s) of action of SBC3 remains to be fully elucidated. Label-free quantitative proteomics was applied to analyse changes in protein abundance in the pathogenic yeast Candida parapsilosis in response to SBC3 treatment. An increased abundance of proteins associated with detoxification and drug efflux were indicative of a cell stress response, whilst significant decreases in proteins required for protein and amino acid biosynthesis offer potential insight into the growth-inhibitory mechanisms of SBC3. Guided by the proteomic findings and the prolific biofilm and adherence capabilities of C. parapsilosis, our studies have shown the potential of SBC3 in reducing adherence to epithelial cells and biofilm formation and hence decrease fungal virulence.

Galleria mellonella Larvae as a Model for Investigating Fungal-Host Interactions

Galleria mellonella larvae have become a widely accepted and utilised infection model due to the functional homology displayed between their immune response to infection and that observed in the mammalian innate immune response. Due to these similarities, comparable results to murine studies can be obtained using G. mellonella larvae in assessing the virulence of fungal pathogens and the in vivo toxicity or efficacy of anti-fungal agents. This coupled with their low cost, rapid generation of results, and lack of ethical/legal considerations make this model very attractive for analysis of host-pathogen interactions. The larvae of G. mellonella have successfully been utilised to analyse various fungal virulence factors including toxin and enzyme production in vivo providing in depth analysis of the processes involved in the establishment and progression of fungal pathogens (e.g., Candida spps, Aspergillus spp., Madurella mycetomatis, Mucormycetes, and Cryptococcus neoformans). A variety of experimental endpoints can be employed including analysis of fungal burdens, alterations in haemocyte density or sub-populations, melanisation, and characterisation of infection progression using proteomic, histological or imaging techniques. Proteomic analysis can provide insights into both sides of the host-pathogen interaction with each respective proteome being analysed independently following infection and extraction of haemolymph from the larvae. G. mellonella can also be employed for assessing the efficacy and toxicity of antifungal strategies at concentrations comparable to those used in mammals allowing for early stage investigation of novel compounds and combinations of established therapeutic agents. These numerous applications validate the model for examination of fungal infection and development of therapeutic approaches in vivo in compliance with the need to reduce animal models in biological research.

Selective Metal Chelation by a Thiosemicarbazone Derivative Interferes with Mitochondrial Respiration and Ribosome Biogenesis in Candida albicans

Metal chelation is generally considered as a promising antifungal approach but its specific mechanisms are unclear. Here, we identify 13 thiosemicarbazone derivatives that exert broad-spectrum antifungal activity with potency comparable or superior to that of fluconazole in vitro by screening a small compound library comprising 89 thiosemicarbazone derivatives as iron chelators. Among the hits, 19ak exhibits minimal cytotoxicity and potent activity against either azole-sensitive or azole-resistant fungal pathogens. Mechanism investigations reveal that 19ak inhibits mitochondrial respiration mainly by retarding mitochondrial respiratory chain complex I activity through iron chelation, and further reduces mitochondrial membrane potential and ATP synthesis in Candida albicans. In addition, 19ak inhibits fungal ribosome biogenesis mainly by disrupting intracellular zinc homeostasis. 19ak also stimulates the activities of antioxidant enzymes and decreases reactive oxygen species formation in C. albicans, resulting in an increase in detrimental intracellular reductive stress. However, 19ak has minor effects on mammalian cells in depleting intracellular iron and zinc. Moreover, 19ak exhibits low capacity to induce drug resistance and in vivo efficacy in a Galleria mellonella infection model. These findings uncover retarded fungal mitochondrial respiration and ribosome biogenesis as downstream effects of disruption of iron and zinc homeostasis in C. albicans and provide a basis for the thiosemicarbazone 19ak in antifungal application. IMPORTANCE The increasing incidence of fungal infections and resistance to existing antifungals call for the development of broad-spectrum antifungals with novel mechanisms of action. In this study, we demonstrate that a thiosemicarbazone derivative 19ak selectively inhibits mitochondrial respiration mainly by retarding mitochondrial respiratory chain complex I activity through iron chelation and inhibits ribosome biogenesis mainly by disrupting intracellular zinc homeostasis in C. albicans. In addition, 19ak exhibits low capacity to induce fungal resistance, minimal cytotoxicity, and in vivo antifungal efficacy. This study provides the basis of thiosemicarbazone derivative 19ak as a metal chelator for the treatment of fungal infections.

Genetic Screens of an Anti-Candida Natural Product Using the Heterozygous Saccharomyces cerevisiae Mutant Library

Candida albicans is one of the most common fungal pathogens in humans. Due to the development of resistance to antifungal drugs, today there is a need for finding new antifungal agents with new pharmacological targets for a more efficient management of C. albicans infections. Drug repositioning or drug repurposing has been exploited to develop new antifungal approaches. Natural products may be more easily developed because they have been a useful source of active antimicrobials. Additionally, new antifungals are needed to combat drug-resistant infections caused by fungi such as by Candida species. Once compounds are identified, determining the mode of action (MOA) of natural products is a key objective. Genetic screens utilizing the Saccharomyces cerevisiae heterozygous mutant library provides a direct link between a phenotypic screen (easy read-out) and the identity of the gene target. Screens using mutant libraries can identify chemical-genetic interactions and genes or pathways affected by compounds to decipher the mechanism of action. Herein, we describe a genetic screen of an anti-Candida natural product.

Assessment of the In Vitro and In Vivo Antifungal Activity of NSC319726 against Candida auris

Candida auris is an emerging yeast pathogen of candidemia with the ability to develop resistance to all current antifungal drug classes. Novel antifungal therapies against C. auris are warranted. NSC319726 is a thiosemicarbazone with an inhibitory effect on fungal ribosome biogenesis that has demonstrated some antifungal activity. In this study, we assessed the in vitro activity and in vivo efficacy of NSC319726 against C. auris. NSC319726 was active in vitro against 22 C. auris isolates from different clades, with MICs ranging from 0.125 to 0.25 mg/liter. Despite complete visual growth inhibition, the effect was described as fungistatic in time-kill curves. Interactions with fluconazole, amphotericin B, and micafungin, as tested by the checkerboard dilution method, were described as indifferent. NSC319726 demonstrated significant effects in rescuing G. mellonella larvae infected with two distinct C. auris isolates, compared to the untreated group. In conclusion, NSC319726 demonstrated in vitro activity against C. auris and in vivo efficacy in an invertebrate model of infection. Its potential role as a novel antifungal therapy in humans should be further investigated. IMPORTANCE Candida auris is emerging as a major public health threat because of its ability to cause nosocomial outbreaks of severe invasive candidiasis. Management of C. auris infection is difficult because of its frequent multidrug-resistant profile for currently licensed antifungals. Here, we show that the thiosemicarbazone NSC319726 was active in vitro against a large collection of C. auris isolates from different clades. Moreover, the drug was well tolerated and effective for the treatment of C. auris infection in an invertebrate model of Galleria mellonella. We conclude that NSC319726 might represent an interesting drug candidate for the treatment of C. auris infection.

Current and promising pharmacotherapeutic options for candidiasis

Introduction: Candida spp. are commensal yeasts capable of causing infections such as superficial, oral, vaginal, or systemic infections. Despite medical advances, the antifungal pharmacopeia remains limited and the development of alternative strategies is needed.Areas covered: We discuss available treatments for Candida spp. infections, highlighting advantages and limitations related to pharmacokinetics, cytotoxicity, and antimicrobial resistance. Moreover, we present new perspectives to improve the activity of the available antifungals, discussing their immunomodulatory potential and advances on drug delivery carriers. New therapeutic approaches are presented including recent synthesized antifungal compounds (Enchochleated-Amphotericin B, tetrazoles, rezafungin, enfumafungin, manogepix and arylamidine); drug repurposing using a diversity of antibacterial, antiviral and non-antimicrobial drugs; combination therapies with different compounds or photodynamic therapy; and innovations based on nano-particulate delivery systems.Expert opinion: With the lack of novel drugs, the available assets must be leveraged to their best advantage through modifications that enhance delivery, efficacy, and solubility. However, these efforts are met with continuous challenges presented by microbes in their infinite plight to resist and survive therapeutic drugs. The pharmacotherapeutic options in development need to focus on new antimicrobial targets. The success of each antimicrobial agent brings strategic insights to the next phased approach in treatingCandida spp. infections.

Systematic Analysis of Functionally Related Gene Clusters in the Opportunistic Pathogen, Candida albicans

The proper balance of gene expression is essential for cellular health, organismal development, and maintaining homeostasis. In response to complex internal and external signals, the cell needs to modulate gene expression to maintain proteostasis and establish cellular identity within its niche. On a genome level, single-celled prokaryotic microbes display clustering of co-expressed genes that are regulated as a polycistronic RNA. This phenomenon is largely absent from eukaryotic microbes, although there is extensive clustering of co-expressed genes as functional pairs spread throughout the genome in Saccharomyces cerevisiae. While initial analysis demonstrated conservation of clustering in divergent fungal lineages, a comprehensive analysis has yet to be performed. Here we report on the prevalence, conservation, and significance of the functional clustering of co-regulated genes within the opportunistic human pathogen, Candida albicans. Our analysis reveals that there is extensive clustering within this organism-although the identity of the gene pairs is unique compared with those found in S. cerevisiae-indicating that this genomic arrangement evolved after these microbes diverged evolutionarily, rather than being the result of an ancestral arrangement. We report a clustered arrangement in gene families that participate in diverse molecular functions and are not the result of a divergent orientation with a shared promoter. This arrangement coordinates the transcription of the clustered genes to their neighboring genes, with the clusters congregating to genomic loci that are conducive to transcriptional regulation at a distance.

Antifungal Drug Repurposing

Control of fungal pathogens is increasingly problematic due to the limited number of effective drugs available for antifungal therapy. Conventional antifungal drugs could also trigger human cytotoxicity associated with the kidneys and liver, including the generation of reactive oxygen species. Moreover, increased incidences of fungal resistance to the classes of azoles, such as fluconazole, itraconazole, voriconazole, or posaconazole, or echinocandins, including caspofungin, anidulafungin, or micafungin, have been documented. Of note, certain azole fungicides such as propiconazole or tebuconazole that are applied to agricultural fields have the same mechanism of antifungal action as clinical azole drugs. Such long-term application of azole fungicides to crop fields provides environmental selection pressure for the emergence of pan-azole-resistant fungal strains such as Aspergillus fumigatus having TR34/L98H mutations, specifically, a 34 bp insertion into the cytochrome P450 51A (CYP51A) gene promoter region and a leucine-to-histidine substitution at codon 98 of CYP51A. Altogether, the emerging resistance of pathogens to currently available antifungal drugs and insufficiency in the discovery of new therapeutics engender the urgent need for the development of new antifungals and/or alternative therapies for effective control of fungal pathogens. We discuss the current needs for the discovery of new clinical antifungal drugs and the recent drug repurposing endeavors as alternative methods for fungal pathogen control.

Screening Repurposing Libraries for Identification of Drugs with Novel Antifungal Activity

Fungal organisms are ubiquitous in nature, and progress of modern medicine is creating an expanding number of severely compromised patients susceptible to a variety of opportunistic fungal infections. These infections are difficult to diagnose and treat, leading to high mortality rates. The limited antifungal arsenal, the toxicity of current antifungal drugs, the development of resistance, and the emergence of new multidrug-resistant fungi, all highlight the urgent need for new antifungal agents. Unfortunately, the development of a novel antifungal is a rather long and expensive proposition, and no new classes of antifungal agents have reached the market in the last 2 decades. Drug repurposing, or finding new indications for old drugs, represents a promising alternative pathway to drug development that is particularly appealing within the academic environment. In the last few years, there has been a growing interest in repurposing approaches in the antifungal arena, with multiple groups of investigators having performed screenings of different repurposing libraries against different pathogenic fungi in search for drugs with previously unrecognized antifungal effects. Overall, these repurposing efforts may lead to the fast deployment of drugs with novel antifungal activity, which can rapidly bring benefits to patients, while at the same time reducing health care costs.

Known Antimicrobials Versus Nortriptyline in Candida albicans: Repositioning an Old Drug for New Targets

Candida albicans has the capacity to develop resistance to commonly used antimicrobials, and to solve this problem, drug repositioning and new drug combinations are being studied. Nortriptyline, a tricyclic antidepressant, was shown to have the capacity to inhibit biofilm and hyphae formation, along with the ability to efficiently kill cells in a mature biofilm. To use nortriptyline as a new antimicrobial, or in combination with known drugs to increase their actions, it is important to characterize in more detail the effects of this drug on the target species. In this study, the Candida albicans GRACE™ collection and a Haplo insufficiency profiling were employed to identify the potential targets of nortriptyline, and to classify, in a parallel screening with amphotericin B, caspofungin, and fluconazole, general multi-drug resistance genes. The results identified mutants that, during biofilm formation and upon treatment of a mature biofilm, are sensitive or tolerant to nortriptyline, or to general drug treatments. Gene ontology analysis recognized the categories of ribosome biogenesis and spliceosome as enriched upon treatment with the tricyclic antidepressant, while mutants in oxidative stress response and general stress response were commonly retrieved upon treatment with any other drug. The data presented suggest that nortriptyline can be considered a “new” antimicrobial drug with large potential for application to in vivo infection models.

Transcriptome profiling reveals insertional mutagenesis suppressed the expression of candidate pathogenicity genes in honeybee fungal pathogen, Ascosphaera apis

Chalkbrood disease is caused by Ascosphaera apis which severely affects honeybee brood. Spore inoculation experiments shown pathogenicity varies among different strains and mutants, however, the molecular mechanism of pathogenicity is unclear. We sequenced, assembled and annotated the transcriptomes of wild type (SPE1) and three mutants (SPE2, SPE3 and SPE4) with reduced pathogenicity that were constructed in our previous study. Illumina sequencing generated a total of 394,910,604 clean reads and de novo Trinity-based assembled into 12,989 unigenes, among these, 9,598 genes were successfully annotated to known proteins in UniProt database. A total of 172, 3,996, and 650 genes were up-regulated and 4,403, 2,845, and 3,016 genes were down-regulated between SPE2-SPE1, SPE3-SPE1, and SPE4-SPE1, respectively. Overall, several genes with a potential role in fungal pathogenicity were detected down-regulated in mutants including 100 hydrolytic enzymes, 117 transcriptional factors, and 47 cell wall related genes. KEGG pathway enrichment analysis reveals 216 genes involved in nine pathways were down-regulated in mutants compared to wild type. The down-regulation of more pathways involved in pathogenicity in SPE2 and SPE4 than SPE3 supports their lower pathogenicity during in-vitro bioassay experiment. Expression of 12 down-regulated genes in mutants was validated by quantitative real time PCR. This study provides valuable information on transcriptome variation caused by mutation for further functional validation of candidate pathogenicity genes in A. apis.

The antifungal pipeline: the need is established. Are there new compounds?

Our review summarizes and compares the temporal development (eras) of antifungal drug discovery as well as antibacterial ventures. The innovation gap that occurred in antibacterial discovery from 1960 to 2000 was likely due to tailoring of existing compounds to have better activity than predecessors. Antifungal discovery also faced innovation gaps. The semi-synthetic antibiotic era was followed closely by the resistance era and the heightened need for new compounds and targets. With the immense contribution of comparative genomics, antifungal targets became part of the discovery focus. These targets by definition are absolutely required to be fungal- or even lineage (clade) specific. Importantly, targets need to be essential for growth and/or have important roles in disease and pathogenesis. Two types of antifungals are discussed that are mostly in the FDA phase I–III clinical trials. New antifungals are either modified to increase bioavailability and stability for instance, or are new compounds that inhibit new targets. One of the important developments in incentivizing new antifungal discovery has been the prolific number of publications of global and country-specific incidence. International efforts that champion global antimicrobial drug discovery are discussed. Still, interventions are needed. The current pipeline of antifungals and alternatives to antifungals are discussed including vaccines.

Identification of Off-Patent Drugs That Show Synergism with Amphotericin B or That Present Antifungal Action against Cryptococcus neoformans and Candida spp

Amphotericin B (AmB) is the antifungal with the strongest fungicidal activity, but its use has several limitations, mainly associated with its toxicity. Although some lipidic and liposomal formulations that present reduced toxicity are available, their price limits their application in developing countries. Flucytosine (5FC) has shown synergistic effect with AmB for treatment of some fungal infections, such as cryptococcosis, but again, its price is a limitation for its use in many regions. In the present work, we aimed to identify new drugs that have a minor effect on Cryptococcus neoformans, reducing its growth in the presence of subinhibitory concentrations of AmB. In the initial screening, we found fourteen drugs that had this pattern. Later, checkerboard assays of selected compounds, such as erythromycin, riluzole, nortriptyline, chenodiol, nisoldipine, promazine, chlorcyclizine, cloperastine, and glimepiride, were performed and all of them confirmed for their synergistic effect (fractional inhibitory concentration index [FICI] < 0.5). Additionally, toxicity of these drugs in combination with AmB was tested in mammalian cells and in zebrafish embryos. Harmless compounds, such as the antibiotic erythromycin, were found to have synergic activity with AmB, not only against C. neoformans but also against some Candida spp., in particular against Candida albicans In parallel, we identified drugs that had antifungal activity against C. neoformans and found 43 drugs that completely inhibited the growth of this fungus, such as ciclopirox and auranofin. Our results expand our knowledge about antifungal compounds and open new perspectives in the treatment of invasive mycosis based on repurposing off-patent drugs.

New inhibitors of homoserine dehydrogenase from Paracoccidioides brasiliensis presenting antifungal activity

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by fungi of the genus Paracoccidioides spp., which mainly affects workers in rural regions of Latin America. Although the antifungal agents currently available for the treatment of PCM are effective in controlling the disease, many months are needed for healing, making the side effects and drug interactions relevant. In addition, conventional treatments are not able to control the sequelae left by PCM, even after the cure, justifying the search for new therapeutic options against PCM. In this context, the enzyme homoserine dehydrogenase of P. brasiliensis (PbHSD) was used to screen a library of natural products from the Zinc database using three different docking programs, i.e. Autodock, Molegro, and CLC Drugdiscovery Workbench. Three molecules (Zinc codes 2123137, 15967722, and 20611644) were better ranked than the homoserine substrate (HSE) and were used for in vitro trials of the minimum inhibitory concentration (MIC) and minimal fungicidal concentration (MCF). All three molecules presented a fungicidal profile with MICs/MCFs of 8, 32, and 128 μg mL^-1, respectively. The two most promising molecules presented satisfactory results with wide therapeutic ranges in the cytotoxicity assays. Molecular dynamics simulations of PbHSD indicated that the ligands remained bound to the protein by a common mechanism throughout the simulation. The molecule with the lowest MIC value presented the highest number of contacts with the protein. The results presented in this work suggest that the molecule Zinc2123137 may be considered as a hit in the development of new therapeutic options for PCM.

High-Throughput Screen Identifying the Thiosemicarbazone NSC319726 Compound as a Potent Antimicrobial Lead Against Resistant Strains of Escherichia coli

Antibiotic discovery is vital when considering the increasing antimicrobial resistance threat. The aim of this work was to provide a high-throughput screen (HTS) assay using multidrug-resistant Escherichia coli strains to enable further research into antimicrobial lead discovery and identify novel antimicrobials. This study describes a primary HTS of a diverse library of 7884 small molecules against a susceptible E. coli strain. A secondary screening of 112 molecules against four E. coli strains with different susceptibility profiles revealed NSC319726 as a potential antimicrobial lead serving as a novel template. NSC319726 is a good candidate for an analoguing program.

Antifungal drugs: New insights in research & development

The need for better antifungal therapy is commonly accepted in view of the high mortality rates associated with systemic infections, the low number of available antifungal classes, their associated toxicity and the increasing number of infections caused by strains with natural or acquired resistance. The urgency to expand the range of therapeutic options for the treatment of fungal infections has led researchers in recent decades to seek alternative antifungal targets when compared to the conventional ones currently used. Although new potential targets are reported, translating the discoveries from bench to bedside is a long process and most of these drugs fail to reach the patients. In this review, we discuss the development of antifungal drugs focusing on the approach of drug repurposing and the search for novel drugs for classical targets, the most recently described gene targets for drug development, the possibilities of immunotherapy using antibodies, cytokines, therapeutic vaccines and antimicrobial peptides.