Development Of New Antifungal Drugs Research Articles

Antifungal activity of propafenone on Candida spp. strains: interaction with antifungals and possible mechanism of action.

Introduction. The development of new antifungal drugs has become a global priority, given the increasing cases of fungal diseases together with the rising resistance to available antifungal drugs. In this scenario, drug repositioning has emerged as an alternative for such development, with advantages such as reduced research time and costs.Gap statement. Propafenone is an antiarrhythmic drug whose antifungal activity is poorly described, being a good candidate for further study.Aim. This study aims to evaluate propafenone activity against different species of Candida spp. to evaluate its combination with standard antifungals, as well as its possible action mechanism.Methodology. To this end, we carried out tests against strains of Candida albicans, Candida auris, Candida parapsilosis, Candida tropicalis, Candida glabrata and Candida krusei based on the evaluation of the MIC, minimum fungicidal concentration and tolerance level, along with checkerboard and flow cytometry tests with clinical strains and cell structure analysis by scanning electron microscopy (SEM).Results. The results showed that propafenone has a 50% MIC ranging from 32 to 256 µg ml-1, with fungicidal activity and positive interactions with itraconazole in 83.3% of the strains evaluated. The effects of the treatments observed by SEM were extensive damage to the cell structure, while flow cytometry revealed the apoptotic potential of propafenone against Candida spp.Conclusion. Taken together, these results indicate that propafenone has the potential for repositioning as an antifungal drug.

Antifungal activity of β-lapachone against a fluconazole-resistant Candida auris strain.

Candida spp. can be found in the human microbiome. However, immunocompromised patients are likely to develop invasive Candida infections, with mortality rates higher than 50%. The discovery of C. auris, a species that rapidly acquire antifungal resistance, increased the concern about Candida infections. The limited number of antifungal agents and the high incidence of resistance to them make imperative the development of new antifungal drugs. β-lapachone is a biological active naphthoquinone that displays antifungal activity against C. albicans and C. glabrata. The aim of this study was to evaluate if this substance affects C. auris growth and elucidate its mechanism of action. A fluconazole-resistant C. auris isolate was used in this study. The antifungal activity of β-lapachone was determined through microbroth dilution assays, and its mechanism of action was evaluated using fluorescent probes. Interaction with fluconazole and amphotericin B was assessed by disk diffusion assay and checkerboard. β-lapachone inhibited planktonic C. auris cell growth by 92.7%, biofilm formation by 84.9%, and decrease the metabolism of preformed biofilms by 87.1% at 100µg/ml. At 100µg/ml, reductions of 30% and 59% of Calcofluor White and Nile red fluorescences were observed, indicating that β-lapachone affects cell wall chitin and neutral lipids content, respectively. Also, the ratio 590nm/529nm of JC-1 decreased 52%, showing that the compound affects mitochondria. No synergism was observed between β-lapachone and fluconazole or amphotericin B. Data show that β-lapachone may be a promising candidate to be used as monotherapy to treat C. auris resistant infections.

Uncovering a Novel cyp51A Mutation and Antifungal Resistance in Aspergillus fumigatus through Culture Collection Screening.

Aspergillus fumigatus is an important concern for immunocompromised individuals, often resulting in severe infections. With the emergence of resistance to azoles, which has been the therapeutic choice for Aspergillus infections, monitoring the resistance of these microorganisms becomes important, including the search for mutations in the cyp51A gene, which is the gene responsible for the mechanism of action of azoles. We conducted a retrospective analysis covering 478 A. fumigatus isolates. This comprehensive dataset comprised 415 clinical isolates and 63 isolates from hospital environmental sources. For clinical isolates, they were evaluated in two different periods, from 1998 to 2004 and 2014 to 2021; for environmental strains, one strain was isolated in 1998, and 62 isolates were evaluated in 2015. Our primary objectives were to assess the epidemiological antifungal susceptibility profile; trace the evolution of resistance to azoles, Amphotericin B (AMB), and echinocandins; and monitor cyp51A mutations in resistant strains. We utilized the broth microdilution assay for susceptibility testing, coupled with cyp51A gene sequencing and microsatellite genotyping to evaluate genetic variability among resistant strains. Our findings reveal a progressive increase in Minimum Inhibitory Concentrations (MICs) for azoles and AMB over time. Notably, a discernible trend in cyp51A gene mutations emerged in clinical isolates starting in 2014. Moreover, our study marks a significant discovery as we detected, for the first time, an A. fumigatus isolate carrying the recently identified TR46/F495I mutation within a sample obtained from a hospital environment. The observed cyp51A mutations underscore the ongoing necessity for surveillance, particularly as MICs for various antifungal classes continue to rise. By conducting resistance surveillance within our institution's culture collection, we successfully identified a novel TR46/F495I mutation in an isolate retrieved from the hospital environment which had been preserved since 1998. Moreover, clinical isolates were found to exhibit TR34/L98H/S297T/F495I mutations. In addition, we observed an increase in MIC patterns for Amphotericin B and azoles, signaling a change in the resistance pattern, emphasizing the urgent need for the development of new antifungal drugs. Our study highlights the importance of continued monitoring and research in understanding the evolving challenges in managing A. fumigatus infections.

Casein kinase 2 complex: a central regulator of multiple pathobiological signaling pathways in Cryptococcus neoformans.

The casein kinase 2 (CK2) complex has garnered extensive attention over the past decades as a potential therapeutic target for diverse human diseases, including cancer, diabetes, and obesity, due to its pivotal roles in eukaryotic growth, differentiation, and metabolic homeostasis. While CK2 is also considered a promising antifungal target, its role in fungal pathogens remains unexplored. In this study, we investigated the functions and regulatory mechanisms of the CK2 complex in Cryptococcus neoformans, a major cause of fungal meningitis. The cryptococcal CK2 complex consists of a single catalytic subunit, Cka1, and two regulatory subunits, Ckb1 and Ckb2. Our findings show that Cka1 plays a primary role as a protein kinase, while Ckb1 and Ckb2 have major and minor regulatory functions, respectively, in growth, cell cycle control, morphogenesis, stress response, antifungal drug resistance, and virulence factor production. Interestingly, triple mutants lacking all three subunits (cka1Δ ckb1Δ ckb2Δ) exhibited more severe phenotypic defects than the cka1Δ mutant alone, suggesting that Ckb1/2 may have Cka1-independent functions. In a murine model of systemic cryptococcosis, cka1Δ and cka1Δ ckb1Δ ckb2Δ mutants showed severely reduced virulence. Transcriptomic, proteomic, and phosphoproteomic analyses further revealed that the CK2 complex controls a wide array of effector proteins involved in transcriptional regulation, cell cycle control, nutrient metabolisms, and stress responses. Most notably, CK2 disruption led to dysregulation of key signaling cascades central to C. neoformans pathogenicity, including the Hog1, Mpk1 MAPKs, cAMP/PKA, and calcium/calcineurin signaling pathways. In summary, our study provides novel insights into the multifaceted roles of the fungal CK2 complex and presents a compelling case for targeting it in the development of new antifungal drugs.IMPORTANCEThe casein kinase 2 (CK2) complex, crucial for eukaryotic growth, differentiation, and metabolic regulation, presents a promising therapeutic target for various human diseases, including cancer, diabetes, and obesity. Its potential as an antifungal target is further highlighted in this study, which explores CK2's functions in C. neoformans, a key fungal meningitis pathogen. The CK2 complex in C. neoformans, comprising the Cka1 catalytic subunit and Ckb1/2 regulatory subunits, is integral to processes like growth, cell cycle, morphogenesis, stress response, drug resistance, and virulence. Our findings of CK2's role in regulating critical signaling pathways, including Hog1, Mpk1 MAPKs, cAMP/PKA, and calcium/calcineurin, underscore its importance in C. neoformans pathogenicity. This study provides valuable insights into the fungal CK2 complex, reinforcing its potential as a target for novel antifungal drug development and pointing out a promising direction for creating new antifungal agents.

Precision-cut lung slices as an ex vivo model to study Pneumocystis murina survival and antimicrobial susceptibility.

Our study reveals the potential of precision-cut lung slices as an ex vivo platform to study the growth/survival of Pneumocystis spp. that can facilitate the development of new anti-fungal drugs.

Synergistic effect of eravacycline combined with fluconazole against resistant Candida albicans in vitro and in vivo

ABSTRACT Background The limited availability of antifungal drugs for candidiasis and the persistent problem of drug resistance, necessitates the urgent development of new antifungal drugs and alternative treatment options. Research design and methods This study examined the synergistic antifungal activity of the combination of eravacycline (ERV) and fluconazole (FLC) both in vitro by microdilution checkerboard assay and in vivo by Galleria mellonella model. The underlying synergistic mechanisms of this drug combination was investigated using RNA-sequencing and qPCR. Results ERV (2 μg/mL) + FLC (0.25–0.5 μg/mL) had strong synergistic antifungal activity against resistant Candida albicans (C. albicans) in vitro, as evidenced by a fractional inhibitory concentration index of 0.0044–0.0088. In vivo experiments in Galleria mellonella larvae infected with resistant C. albicans revealed that ERV (2 μg/larva) + FLC (1 μg/larva) improved survival rates and reduced fungal burden. The results of RNA-sequencing and qPCR showed that the mechanism of synergistic inhibition on resistant C. albicans was related to the inhibition of DNA replication and cell meiosis. Conclusions These results indicate that the combination of ERV and FLC effectively inhibits resistant C. albicans both in vitro and in vivo and lay the foundation for a potential novel treatment option for candidiasis.

Antifungal activity of sustainable histone deacetylase inhibitors against planktonic cells and biofilms of Candida spp. and Cryptococcus neoformans.

The limited therapeutic options for fungal infections and the increased incidence of fungal strains resistant to antifungal drugs, especially Candida spp., require the development of new antifungal drugs and strategies. Histone deacetylase inhibitors (HDACi), like vorinostat, have been studied in cancer treatment and have antifungal effects, acting alone or synergistically with classical antifungals. Here we investigated the antifungal activity of two novel sustainable HDACi (LDT compounds) based on vorinostat structure. In docking simulations, all HDACi analyzed can bind to Class-I HDACs of Candida albicans, Candida tropicalis, and Cryptococcus neoformans, which have similar shapes to vorinostat binding. LDT compounds showed moderate activity when tested alone against fungi but act synergistically with antifungal azoles against Candida spp. They reduced biofilm formation by more than 50% in C. albicans (4µg/mL), with the main action in fungal filamentation. Cytotoxicity of the LDT compounds against RAW264.7 cells was evaluated and LDT536 demonstrated cytotoxicity only at the concentration of 200µmol/L, while LDT537 showed IC50 values of 29.12µmol/L. Our data indicated that these sustainable and inexpensive HDACi have potential antifungal and antibiofilm activities, with better results than vorinostat, although further studies are necessary to better understand the mechanism against fungal cells.

The potential role of plant secondary metabolites on antifungal and immunomodulatory effect.

With the widespread use of antibiotic drugs worldwide and the global increase in the number of immunodeficient patients, fungal infections have become a serious threat to global public health security. Moreover, the evolution of fungal resistance to existing antifungal drugs is on the rise. To address these issues, the development of new antifungal drugs or fungal inhibitors needs to be targeted urgently. Plant secondary metabolites are characterized by a wide variety of chemical structures, low price, high availability, high antimicrobial activity, and few side effects. Therefore, plant secondary metabolites may be important resources for the identification and development of novel antifungal drugs. However, there are few studies to summarize those contents. In this review, the antifungal modes of action of plant secondary metabolites toward different types of fungi and fungal infections are covered, as well as highlighting immunomodulatory effects on the human body. This review of the literature should lay the foundation for research into new antifungal drugs and the discovery of new targets. KEY POINTS: • Immunocompromised patients who are infected the drug-resistant fungi are increasing. • Plant secondary metabolites toward various fungal targets are covered. • Plant secondary metabolites with immunomodulatory effect are verified in vivo.

A first-in-class inhibitor of Hsp110 molecular chaperones of pathogenic fungi

Proteins of the Hsp110 family are molecular chaperones that play important roles in protein homeostasis in eukaryotes. The pathogenic fungus Candida albicans, which causes infections in humans, has a single Hsp110, termed Msi3. Here, we provide proof-of-principle evidence supporting fungal Hsp110s as targets for the development of new antifungal drugs. We identify a pyrazolo[3,4-b] pyridine derivative, termed HLQ2H (or 2H), that inhibits the biochemical and chaperone activities of Msi3, as well as the growth and viability of C. albicans. Moreover, the fungicidal activity of 2H correlates with its inhibition of in vivo protein folding. We propose 2H and related compounds as promising leads for development of new antifungals and as pharmacological tools for the study of the molecular mechanisms and functions of Hsp110s.

Food and Drug Administration Public Workshop Summary-Development Considerations of Antifungal Drugs to Address Unmet Medical Need.

Pressing challenges in the treatment of invasive fungal infections (IFIs) include emerging and rare pathogens, resistant/refractory infections, and antifungal armamentarium limited by toxicity, drug-drug interactions, and lack of oral formulations. Development of new antifungal drugs is hampered by the limitations of the available diagnostics, clinical trial endpoints, prolonged trial duration, difficulties in patient recruitment, including subpopulations (eg, pediatrics), and heterogeneity of the IFIs. On 4 August 2020, the US Food and Drug Administration convened a workshop that included IFI experts from academia, industry, and other government agencies to discuss the IFI landscape, unmet need, and potential strategies to facilitate the development of antifungal drugs for treatment and prophylaxis. This article summarizes the key topics presented and discussed during the workshop, such as incentives and research support for drug developers, nonclinical development, clinical trial design challenges, lessons learned from industry, and potential collaborations to facilitate antifungal drug development.

Evaluation of Protein Kinase C Inhibition of some Benzofuro[3,2-d]pyrimidine Derivatives

Abstract: Treatment of fungal infections is very difficult because of the limited therapeutic arsenal and the emergence of resistance to the two major antifungal classes: azoles and echinocandins. Consequently, finding new targets and new therapeutic strategies is a priority. The protein kinase Pkc1 of Candida albicans (CaPkc1), one of the key proteins involved in MAPK pathways, is described as a regulator of cell wall integrity during growth, morphogenesis, and response to cell wall stress. Therefore, the discovery of CaPkc1 inhibitory molecules can open up new and promising prospects in the development of new antifungal drugs that inhibit CaPkc1. In this study, we evaluated the CaPkc1 inhibitory activity of three benzofuro[3,2-d]pyrimidine derivatives at three different concentrations of 50 µM, 100 µM, and 150 µM. A concentration of 100 μM was optimal for CaPkc1 inhibitory activity with all three benzofuro[3,2-d]pyrimidine derivatives.
 Keywords: Benzofuro[3,2-d]pyrimidine, CaPkc1, Candida albicans, antifungal activity. 
 

2nd Workshop in Microbial Molecular Biology

2nd Workshop in Microbial Molecular Biology

Combined Transcriptome and Metabolome Analysis Reveals That the Potent Antifungal Pyrylium Salt Inhibits Mitochondrial Complex I in Candida albicans.

Based on the structural modification of SM21, xy12, a new pyrylium salt derivative with enhanced antifungal activities, was synthesized. The MICs (MIC90) of xy12 against Candida albicans ranged from 0.125 to 0.25 μg/mL, about 2-fold lower than those of SM21. In addition, xy12 inhibited hypha and biofilm formation in C. albicans in a dose-dependent manner. A total of 3,454 differentially expressed genes and 260 differential metabolites were identified in the xy12-treated C. albicans by RNA-seq and non-targeted metabolomics. By integrating KEGG pathway enrichment analysis, we found that inhibition of oxidative phosphorylation was the important antifungal mechanism of action of xy12. Electron transport through mitochondrial respiratory complexes I to IV is the common process of oxidative phosphorylation. Compared with the sensitivity of the wild-type SC5314 to xy12, decreased sensitivities in mitochondrial complex I (CI)-deficient mutants and increased sensitivities in mitochondrial complex III- and IV-deficient mutants suggested that the antifungal effects of xy12 were dependent on CI. Consistently, xy12 exhibited antagonism with rotenone, an inhibitor of CI, and significantly inhibited the expression and activity of CI. Meanwhile, the phenotypes in the xy12-treated C. albicans were similar to those in the CI-deficient mutants, such as decreased ATP production, reduced mitochondrial membrane potential, loss of mitochondrial DNA, inability to utilize nonfermentative carbon sources, and decreased cell wall N-linked mannoproteins. Collectively, our results revealed that the pyrylium salt xy12 could constrain oxidative phosphorylation by inhibiting mitochondrial complex I in C. albicans, providing a novel lead compound for the development of mitochondria-targeted antifungal drugs. IMPORTANCE The development of new antifungal drugs is critical for solving the problem of antifungal resistance and expanding the limited variety of clinical antifungal drugs. Based on the modification of the pyrylium salt SM21, a new lead compound, xy12, was synthesized which was effective against Candida species both in vitro and in vivo. In this study, conjoined analysis of the transcriptome and metabolome elucidated the antifungal mechanism of action of xy12, which inhibited the activity of mitochondrial complex I in C. albicans. Targeting fungi-specific mitochondrial complex proteins has been reported as a promising antifungal strategy. Our study provided a new lead compound for targeting C. albicans mitochondrial complex I, which could be beneficial for discovering novel antifungal drugs.

Synergistic Antifungal Interactions between Antibiotic Amphotericin B and Selected 1,3,4-thiadiazole Derivatives, Determined by Microbiological, Cytochemical, and Molecular Spectroscopic Studies.

In recent years, drug-resistant and multidrug-resistant fungal strains have been more frequently isolated in clinical practice. This phenomenon is responsible for difficulties in the treatment of infections. Therefore, the development of new antifungal drugs is an extremely important challenge. Combinations of selected 1,3,4-thiadiazole derivatives with amphotericin B showing strong synergic antifungal interactions are promising candidates for such formulas. In the study, microbiological, cytochemical, and molecular spectroscopy methods were used to investigate the antifungal synergy mechanisms associated with the aforementioned combinations. The present results indicate that two derivatives, i.e., C1 and NTBD, demonstrate strong synergistic interactions with AmB against some Candida species. The ATR-FTIR analysis showed that yeasts treated with the C1 + AmB and NTBD + AmB compositions, compared with those treated with single compounds, exhibited more pronounced abnormalities in the biomolecular content, suggesting that the main mechanism of the synergistic antifungal activity of the compounds is related to a disturbance in cell wall integrity. The analysis of the electron absorption and fluorescence spectra revealed that the biophysical mechanism underlying the observed synergy is associated with disaggregation of AmB molecules induced by the 1,3,4-thiadiazole derivatives. Such observations suggest the possibility of the successful application of thiadiazole derivatives combined with AmB in the therapy of fungal infections.

Chemical Profile, Anti-Microbial and Anti-Inflammaging Activities of Santolina rosmarinifolia L. Essential Oil from Portugal.

Fungal infections and the accompanying inflammatory responses are associated with great morbidity and mortality due to the frequent relapses triggered by an increased resistance to antifungal agents. Furthermore, this inflammatory state can be exacerbated during inflammaging and cellular senescence. Essential oils (EO) are receiving increasing interest in the field of drug discovery due to their lipophilic nature and complex composition, making them suitable candidates in the development of new antifungal drugs and modulators of numerous molecular targets. This work chemically characterized the EO from Santolina rosmarinifolia L., collected in Setúbal (Portugal), and assessed its antifungal potential by determining its minimum inhibitory (MIC) and minimum lethal (MLC) concentration in accordance with the Clinical Laboratory Standard Guidelines (CLSI) guidelines, as well as its effect on several Candida albicans virulence factors. The anti-inflammatory effect was unveiled using lipopolysaccharide (LPS)-stimulated macrophages by assessing several pro-inflammatory mediators. The wound healing and anti-senescence potential of the EO was also disclosed. The EO was mainly characterized by β-pinene (29.6%), borneol (16.9%), myrcene (15.4%) and limonene (5.7%). It showed a strong antifungal effect against yeasts and filamentous fungi (MIC = 0.07-0.29 mg/mL). Furthermore, it inhibited dimorphic transition (MIC/16), decreased biofilm formation with a preeminent effect after 24 h (MIC/2) and disrupted preformed biofilms in C. albicans. Additionally, the EO decreased nitric oxide (NO) release (IC50 = 0.52 mg/mL) and pro-IL-1β and inducible nitric oxide synthase (iNOS) expression in LPS-stimulated macrophages, promoted wound healing (91% vs. 81% closed wound) and reduced cellular senescence (53% vs. 73% β-galactosidase-positive cells). Overall, this study highlights the relevant pharmacological properties of S. rosmarinifolia, opening new avenues for its industrial exploitation.

Extracellular Enzymatic Activity of Candida Species Isolated from Patients with Head and Neck Cancer Undergoing Radiation Therapy and Its Correlation with Mucositis: A Cross-Sectional Study

Introduction: The differences in enzymatic activity expressed by various Candida species determine their virulence and play a pivotal role in understanding the pathogenesis of candidiasis. Additionally, this knowledge aids in the development of new antifungal drugs that target these enzymes, thereby enhancing therapeutic approaches. Understanding the extracellular enzymatic activity of Candida species is crucial for the development of new anticandidial drugs targeting these enzymes. Aim: To determine the differences in enzymatic activity expressed by various Candida species isolated from patients with Head and Neck Cancer (HNC) undergoing Radiation Therapy (RT) and to correlate these differences with the severity of mucositis. Materials and Methods: This cross-sectional study evaluated the enzymatic activity of Candida species, including C. albicans and Non albicans Candida species (NAC), isolated from HNC patients undergoing RT at the radiation oncology department, Amala Institute of Medical Sciences, Thrissur, Kerala, India. A total of 276 patients were enrolled in the study over a four-year period (January 2019 to December 2022). Extracellular enzymatic activities such as proteinase, phospholipase, haemolysin, and esterase were detected using the plate method, as described previously. Mucositis was graded according to the Radiation Therapy Oncology Group (RTOG) criteria. Data were analysed using Statistical Package for the Social Sciences (SPSS) version 23.0 (IBM, Illinois, US). The Chi-square test was used to analyse the variables, and the unpaired t-test was used to compare enzymatic activity. Spearman’s rank correlation was used to identify any correlation between mucositis and extracellular enzymatic activity. Results: A total of 97 Candida strains (56 C. albicans and 41 NAC) were isolated. There was no statistically significant difference between C. albicans and NAC species causing infections in men and women (p-value=0.390), as well as in those with diabetes (p-value=0.127) and hypertension (p-value=0.979). Proteinase, haemolytic activity, and esterase production were detected in 88 (90.7%), 84 (86.6%), and 67 (69.0%) isolates, respectively, while phospholipase activity was shown by 18 (18.5%) isolates. There was no statistically significant difference between C. albicans and NAC species regarding the mean phospholipase, proteinase, haemolysin, and esterase activity (p-value>0.05). C. albicans exhibited high activity for all four enzymes, while a considerable percentage of NAC showed moderate activity. High phospholipase and proteinase activity in C. albicans showed a good correlation (r=0.148 and r=0.186, respectively) with mucositis. Conclusion: C. albicans showed high activity for all four enzymes, indicating its virulence. The majority of C. albicans strains exhibited proteinase activity, which is associated with the severity of mucosal infections. The phospholipase activity has the potential to play a role in the emergence of drug resistance and should be closely monitored.

Antifungal Effect and Inhibition of the Virulence Mechanism of D-Limonene against Candida parapsilosis.

Yeasts from the Candida parapsilosis complex are clinically relevant due to their high virulence and pathogenicity potential, such as adherence to epithelial cells and emission of filamentous structures, as well as their low susceptibility to antifungals. D-limonene, a natural compound, emerges as a promising alternative with previously described antibacterial, antiparasitic, and antifungal activity; however, its mechanisms of action and antivirulence activity against C. parapsilosis complex species have not been elucidated. Therefore, in the present study, we aimed to evaluate the antifungal and antivirulence action, as well as the mechanism of action of D-limonene against isolates from this complex. D-limonene exhibited relevant antifungal activity against C. parapsilosis complex yeasts, as well as excellent antivirulence activity by inhibiting yeast morphogenesis and adherence to the human epithelium. Furthermore, the apoptotic mechanism induced by this compound, which is not induced by oxidative stress, represents an important target for the development of new antifungal drugs.

Understanding the environmental drivers of clinical azole resistance in Aspergillus species.

Aspergilli are ubiquitous fungal pathogens associated with severe life-threatening infections, especially in immunocompromised patients. Azoles are the first line of defence in the fight against most Aspergillus -related infections. However, resistance to these therapeutic compounds has developed, which is mainly due to the existence of mutations in lanosterol 14 alpha-demethylase (Cyp51A), a crucial enzyme in the pathway that produces ergosterol and is the target of azole antifungals. Azole-based antifungal medications are ineffective because of infections brought on by azole-resistant Aspergillus species, leading to a high fatality rate. However, resistant Aspergillus isolates have also been isolated from azole-naïve patients. Global agricultural practices promote the use of azole fungicides to protect crops from phytopathogens. Usage of azole fungicides on a large scale has been linked to the development of resistance among Aspergillus species prevalent in the environment. The infections caused by these azoleresistant Aspergillus species cannot be treated by the available azole drugs, in turn leading to high morbidity and mortality rates. Thus, knowledge of the environmental drivers and comprehending the genetic basis of fungal drug resistance evolution is pertinent, considering increasing numbers of patients with COVID-19 infections who are sensitive to opportunistic fungal infections. This article emphasises the prevalence and underlying mechanisms of azole resistance in Aspergillus species, with a focus on environmental triggers and resistance development. It also highlights the need for regular surveillance of pesticide use in agriculture, detection of triazole-resistant Aspergillus species in environmental and clinical settings and development of new antifungal drugs.

Surface-enhanced Raman spectral characterization of antifungal activity of selenium and zinc based organometallic compounds

Surface-enhanced Raman spectroscopy (SERS) is used to identify the biochemical changes associated with the antifungal activities of selenium and zinc organometallic complexes against Aspergillus niger fungus. These biochemical changes identified in the form of SERS peaks can help to understand the mechanism of action of these antifungal agents which is important for development of new antifungal drugs. The SERS spectral changes indicate the denaturation and conformational changes of proteins and fungal cell wall decomposition in complex exposed fungal samples. The SERS spectra of these organometallic complexes exposed fungi are analyzed by using statistical tools like principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA). PCA is employed to differentiate the SERS spectra of fungal samples exposed to ligands and complexes. The PLS-DA discriminated different groups of spectra with 99.8% sensitivity, 100% specificity, 98% accuracy and 86 % area under receiver operating characteristic (AUROC) curve.

S3.5d Identification of fungicidal activity of otilonium bromide by the repurposing approach

S3.5 Environmental exposure - risk for human fungal disease, September 21, 2022, 4:45 PM - 6:15 PM ObjectivesThe development of new antifungal drugs will help to expand the limited antifungal arsenal and curb the emergence of drug resistance. To meet the demand for novel antifungal drugs, we performed a high-throughput screen of an FDA-approved compound library (HY-L022, MCE®) and identified a promising lead antifungal compound, otilonium bromide (OTB).MethodsWe determined antifungal activity of each compound from the library and investigated the antifungal spectrum of OTB using broth microdilution assays (Fig. 1a). We tested the fungicidal effect of OTB by the spot assay and disk diffusion assay. The inhibitory effect of OTB on mycelial growth was identified by observing hyphal growth in hyphal-inducing media containing OTB. The antibiofilm activity of OTB was evaluated by XTT method. We further checked the antifungal activity of OTB in vivo by a murine C. albicans infection model, which was constructed by immunosuppression of mice with cyclophosphamide, inhibiting the intestinal microorganisms by levofloxacin (14 mg/ml), and then gavage with C. albicans cells (1 × 108 cells per mouse). A total of 24 C57 mice were randomly divided into three groups: one group was gavaged with saline, one group with 1 mg/kg fluconazole, and one group with 50 mg/kg OTB. In all 2 h after infection, drugs were given once a day for 4 consecutive days, with 15 days of observation. The death of a mouse was assessed daily and statistically analyzed by Log-rank (Mantel-Cox) test. The toxicity of OTB to human cloned colon adenocarcinoma cells was assessed with MTT method.ResultsWe found that OTB is the most promising lead antifungal molecule among FDA-approved drugs (Fig. 1a). OTB has a broad-spectrum antifungal activity with minimum inhibitory concentration for inhibiting the growth of 50% of strains (MIC50) values ranging from 0.39 to 6.25 μm (Fig. 1b). We found that OTB (≥3.5 μm) has fungicidal effect on C. albicans using spot assay (Fig. 1c). We further found that OTB (25 μg/disk) can form a clear inhibition zone, but not fluconazole (25 μg/disk) (Fig. 1d). Besides, we spotted C. albicans cells from the broth microdilution assays onto YPD solid medium and found that cells treated with OTB (≥1.56 μm) could not recover on YPD solid medium, while cells treated with FLC could (Fig. 1e). It is worth noting that OTB has inhibitory effects on filamentation and biofilm formation at 12.5 μm (Fig. 2a, b), which are key virulence factors of pathogenic fungi. Besides, OTB (50 mg/kg) significantly prolonged the median survival time from 5 days (control group) to 15 days and improved the survival rate from 0% (control group) to 62.5% (P = .0078) (Fig. 2c). Furthermore, we found that OTB exhibited relative low toxicity to mammal cells with IC50 28-57 μm (Fig. 2d), which was much higher than MIC50 against pathogenic fungi.ConclusionOur study highlights that OTB has a broad-spectrum antifungal activity with low MIC50 values and high safety in vitro and potent antifungal efficacy in vivo and will be beneficial to the treatment of devastating invasive fungal infections.