Unveiling the roles of CaSDH8 in Candida albicans: Implications for virulence and azole resistance

Candida albicans is the most common pathogen in systemic fungal diseases, exhibits a complex pathogenic mechanism, and is increasingly becoming drug tolerant. Therefore, it is particularly important to study the genes associated with virulence and resistance of C. albicans. Here, we identified a gene (orf19.1588) that encodes a conserved mitochondrial protein known as CaSDH8, upon deletion of CaSdh8, the deleted strain (Casdh8Δ/Δ) experienced impaired growth, hyphal development, and virulence. Casdh8Δ/Δ displayed a reduced capacity to utilize alternative carbon sources, along with detrimental alterations in reactive oxygen species (ROS), mitochondrial membrane potential (MMP) depolarization, and adenosine triphosphate (ATP) levels. Interestingly, Casdh8Δ/Δ demonstrated resistance to azole drugs, and under the influence of fluconazole, the cell membrane permeability and mitochondrial function of Casdh8Δ/Δ were less compromised than those of the wild type, indicating a reduction in the detrimental effects of fluconazole on Casdh8Δ/Δ. These findings highlight the significance of CaSDH8 as a crucial gene for the maintenance of cellular homoeostasis. Our study is the first to document the effects of the CaSDH8 gene on the virulence and azole resistance of C. albicans at both the molecular and animal levels, providing new clues and directions for the antifungal infection and the discovery of antifungal drug targets.

Advancing cryptococcal treatment: The role of nanoparticles in mitigating antifungal resistance

Cryptococcus, a ubiquitous and formidable fungal pathogen, contributes to a substantial global disease burden, with nearly 250,000 cases and 181,000 fatalities attributed to cryptococcal meningitis annually worldwide. The invasive nature of Cryptococcus presents significant challenges in treatment and management, as it mostly affects vulnerable populations, including HIV patients, organ transplant recipients, pregnant women, and elderly individuals. Moreover, these difficulties are exacerbated by the development of antifungal resistance, which emphasizes the need for efficient control measures. In this context, research efforts focusing on infection control and novel therapeutic strategies become paramount. Nanoparticle-based therapies emerge as a solution, offering advanced antifungal properties and improved efficacy. Developing effective treatment options requires understanding the complex landscape of cryptococcal infections and the innovative potential of nanoparticle-based therapies. This review highlights the urgent need for novel strategies to combat the growing threat posed by antifungal resistance while offering insights into the intricate realm of cryptococcal infections, particularly focusing on the promising role of nanoparticle-based therapies.

Preparation and evaluation the effects of retinoic acid loaded proliposomal nanofibers on microbial biofilm inhibition

The electrospinning method involves the production of different drug delivery systems using various polymers. The production of proliposomes with electrospinning provides the hybridization of two novel drug delivery systems. Retinoic acid, also known as all-trans retinoic acid (ATRA), is a common and effective drug for acne therapy. This study aimed to prepare ATRA-loaded proliposomal nanofibers and evaluate their effectiveness on microbial biofilm inhibition. Blank and ATRA-loaded proliposomal nanofiber formulations were fabricated in various polyvinylpyrrolidone, phosphatidylcholine and cholesterol ratios. TEM images verified the rapid formation of the liposomes after the hydration of nanofibers. The vesicle size, polydispersity index and zeta potential values of self-assembled liposomes were measured. The vesicle size values were found to be 321.9-363.8 nm with PDI values varying between 0.332 and 0.511 and zeta potential values of (-16.8) to (-20.5)mV. ATRA-loaded proliposomal nanofibers provided higher bioadhesion (0.25 mJ/cm2) than the commercial cream (0.07 mJ/cm2). The short-term stability results showed that the initial characteristics remained for three months at 4 °C. The proposed ATRA-loaded self-assembled proliposomal system provided antibacterial, fungistatic or fungicidal effects superior to retinoic acid itself and inhibited biofilm formation in lower concentrations. This approach can combine the stability advantage of nanofibers in the dry state with the high effectiveness of liposomes in acne treatment presenting antibacterial and anti-biofilm-forming activity against Candida albicans and Cutibacterium acnes.

In-vitro Evaluation of the Antifungal Property of Cold-Pressed Coconut oil Against Drug-Resistant Candida albicans and in-Silico Bioactivity Against Candidapepsin-2

Objective: This study focuses on Candida albicans, a significant fungal pathogen in humans, particularly affecting immunocompromised individuals and developing resistance to commonly used antifungal drugs. To address this challenge, the research assessed the in-vitro anti-candida properties of cold-pressed coconut oil. Additionally, the study conducted an in-silico evaluation of the oil's bioactive compounds against candidapepsin-2, an enzyme crucial in the virulence and pathogenesis of Candida infections. Materials and Methods: Extracted coconut oil was tested for its sterility and evaluated for its antifungal activity in-vitro using the agar well-diffusion methods with fluconazole as a positive control. Growth kinetics assay and synergism activity with fluconazole were also assessed. The coconut oil was quantitatively screened for its bioactive compounds using gas chromatography coupled to a mass spectrophotometer (GC-MS) and the resulting bioactive compounds were assessed for absorption, distribution, metabolism, excretion and toxicity (ADMET) properties using the SWISSADME tool. Compounds that met Lipinski's rule of five (ROF) were subjected to molecular docking against candidapepsin-2 using the Biovia (Discovery) docking tool. Results: The test isolates exhibited zones of inhibition ranging from 47–76 mm to the extract (100%) compared to 12–42 mm exhibited against fluconazole (400 mg) and 2–3 mm in plates containing only agar with MICs and MFCs ranging from 1.57–6.25% and 3.13 −12.5% against the extract compared to the control drug where MICs and MFCs of 6.25–12.5% and 12.5–25.0% were observed, respectively. The coconut extract exerted a concentration-dependent effect on the test isolates over time as higher extract concentrations decreased the optical density of cells to 0.001–0.06 at 72 h of incubation. Equal proportions of the extract + fluconazole exerted greater inhibitory potentials on the test isolates compared with those of low extract proportions. The synergistic-antagonistic antifungal assay showed enhanced sensitivity of the resistant isolates. Of the eleven (11) bioactive compounds quantitatively screened, only nine (9) met Lipinski's ROF and also returned favourable pharmacokinetics comparable to fluconazole. Docking scores for the bioactive compounds ranged from −2.0 to −3.0 kcal/mol. The most recurring amino acid residues following molecular docking were ILE and THR. Conclusion: The bioactive compounds showed desirable activities in-vitro, especially in synergy with fluconazole against the drug-resistant Candida species and in-silico and thus, require further studies to validate their potential use in the management of Candida-related infections.

Infection and Prophylaxis During Normothermic Liver Perfusion: Audit of Incidence and Pharmacokinetics of Antimicrobial Therapy

BACKGROUND

Ex situ normothermic liver perfusion (NMP) in a blood-based perfusate is associated with a risk of microbe growth, resulting in life-threatening posttransplant sepsis. Antibiotics are widely used, but the pharmacokinetics of these agents are unknown as is their efficacy. We wished to assess the perfusate concentrations of the meropenem and fluconazole that we use and to audit the incidence of infection with this antimicrobial therapy.

METHODS

Fluconazole and meropenem (100 mg each) were added to the perfusate before NMP began, and serial samples were taken and assayed for drug concentrations. Perfusate cultures were available from 210 of the 242 perfusions performed between February 1, 2018, and April 6, 2023; these were reviewed.

RESULTS

Following administration of 100 mg fluconazole, levels fell slightly from a median of 24.9 mg/L at 1 h to 22.6 mg/L at 10 h. In contrast, meropenem concentrations fell over time, from a median of 21.8 mg/L at 1 h to 9.4 mg/L at 10 h. There were 4 significant microorganisms grown in the perfusions, including 3 Candida species and an Enterococcus faecium . All the Candida -infected livers were transplanted with no adverse consequences, the recipients being treated with anidulafungin upon identification of the infecting organism; the Enterococcus -infected liver was not transplanted.

CONCLUSIONS

Serious infection is a risk with NMP but appears to be mitigated with a protocol combining fluconazole and meropenem. This combination may not be appropriate in areas where resistance is prevalent. Routine culture of NMP perfusate is essential to identify breakthrough organisms early and enable recipient treatment.

Specifically Targeting Metacaspases of Candida: A New Therapeutic Opportunity

The World Health Organization (WHO) recently published a list of fungal priority pathogens, including Candida albicans and C. auris. The increased level of resistance of Candida is raising concern, considering the availability of only four classes of medicine. The WHO is seeking novel agent classes with different targets and mechanisms of action. Targeting Candida metacaspases to control intrinsic cell death could provide new therapeutic opportunities for invasive candidiasis. In this review, we provide the available evidence for Candida cell death, describe Candida metacaspases, and discuss the potential of Candida metacaspases to offer a new specific target. Targeting Candida cell death has good scientific rationale given that the fungicidal activity of many marketed antifungals is mediated, among others, by cell death triggering. But none of the available antifungals are specifically activating Candida metacaspases, making this target a new therapeutic opportunity for non-susceptible isolates. It is expected that antifungals based on the activation of fungi metacaspases will have a broad spectrum of action, as metacaspases have been described in many fungi, including filamentous fungi. Considering this original mechanism of action, it could be of great interest to combine these new antifungal candidates with existing antifungals. This approach would help to avoid the development of antifungal resistance, which is especially increasing in Candida.

Calcineurin is required for Candida glabrata Pdr1 transcriptional activation

IMPORTANCE

Drug-resistant microorganisms are a problem in the treatment of all infectious diseases; this is an especially acute problem with fungi due to the existence of only three major classes of antifungal drugs, including the azole drug fluconazole. In the pathogenic yeast Candida glabrata, mutant forms of a transcription factor called Pdr1 are commonly associated with decreased fluconazole susceptibility and poor clinical outcomes. Here, we identify a protein phosphatase called calcineurin that is required for fluconazole-dependent induction of Pdr1 transcriptional activation and associated drug susceptibility. Gain-of-function mutant forms of Pdr1 still required the presence of calcineurin to confer normally decreased fluconazole susceptibility. Previous studies showed that calcineurin controls susceptibility to the echinocandin class of antifungal drugs, and our data demonstrate that this protein phosphatase is also required for normal azole drug susceptibility. Calcineurin plays a central role in susceptibility to two of the three major classes of antifungal drugs in C. glabrata.

Understanding fluconazole tolerance in Candida albicans: implications for effective treatment of candidiasis and combating invasive fungal infections

OBJECTIVES

Fluconazole (FLC) tolerant phenotypes in Candida species contribute to persistent candidemia and the emergence of FLC resistance. Therefore, making FLC fungicidal and eliminating FLC tolerance are important for treating invasive fungal diseases (IFDs) caused by Candida species. However, the mechanisms of FLC tolerance in Candida species remain to be fully explored.

METHODS

This review discusses the high incidence of FLC tolerance in Candida species and the importance of successfully clearing FLC tolerance in treating candidiasis. We further define and characterize FLC tolerance in C. albicans.

RESULTS

This review identifies global factors affecting FLC tolerance and suggest that FLC tolerance is a strategy of C. albicans response to FLC damage whose mechanism differs from FLC resistance.

CONCLUSIONS

This review highlights the significance of the cell membrane and cell wall integrity in FLC tolerance, guiding approaches to combat IFDs caused by Candida species..

Cryptococcal meningitis

Cryptococcus neoformans and Cryptococcus gattii species complexes cause meningoencephalitis with high fatality rates and considerable morbidity, particularly in persons with deficient T cell-mediated immunity, most commonly affecting people living with HIV. Whereas the global incidence of HIV-associated cryptococcal meningitis (HIV-CM) has decreased over the past decade, cryptococcosis still accounts for one in five AIDS-related deaths globally due to the persistent burden of advanced HIV disease. Moreover, mortality remains high (~50%) in low-resource settings. The armamentarium to decrease cryptococcosis-associated mortality is expanding: cryptococcal antigen screening in the serum and pre-emptive azole therapy for cryptococcal antigenaemia are well established, whereas enhanced pre-emptive combination treatment regimens to improve survival of persons with cryptococcal antigenaemia are in clinical trials. Short courses (≤7 days) of amphotericin-based therapy combined with flucytosine are currently the preferred options for induction therapy of cryptococcal meningitis. Whether short-course induction regimens improve long-term morbidity such as depression, reduced neurocognitive performance and physical disability among survivors is the subject of further study. Here, we discuss underlying immunology, changing epidemiology, and updates on the management of cryptococcal meningitis with emphasis on HIV-associated disease.

Enhancing the Antifungal Efficacy of Fluconazole with a Diterpene: Abietic Acid as a Promising Adjuvant to Combat Antifungal Resistance in Candida spp

The increasing antifungal resistance rates against conventional drugs reveal the urgent need to search for new therapeutic alternatives. In this context, natural bioactive compounds have a critical role in antifungal drug development. Since evidence demonstrates that abietic acid, a diterpene found in Pinus species, has significant antimicrobial properties, this study aimed to evaluate the antifungal activity of abietic acid against Candida spp and its ability to potentiate the activity of fluconazole. Abietic acid was tested both individually and in combination with fluconazole against Candida albicans (CA INCQS 40006), Candida krusei (CK INCQS 40095), and Candida tropicalis (CT INCQS 40042). The microdilution method was used to determine the IC50 and the cell viability curve. Minimum Fungicidal Concentration (MFC) was determined by subculture in a solid medium. The plasma membrane permeability was measured using a fluorescent SYTOX Green probe. While the IC50 of the drugs alone ranged between 1065 and 3255 μg/mL, the IC50 resulting from the combination of abietic acid and fluconazole ranged between 7563 and 160.1 μg/mL. Whether used in combination with fluconazole or isolated, abietic acid exhibited Minimum Fungicidal Concentration (MFC) values exceeding 1024 μg/mL against Candida albicans, Candida krusei and Candida tropicalis. However, it was observed that the antifungal effect of fluconazole was enhanced when used in combination with abietic acid against Candida albicans and Candida tropicalis. These findings suggest that while abietic acid alone has limited inherent antifungal activity, it can enhance the effectiveness of fluconazole, thereby reducing antifungal resistance.

Synergistic effect of hydralazine associated with triazoles on Candida spp. in planktonic cells

Objective: To evaluate the antifungal activity of hydralazine hydrochloride alone and in synergy with azoles against Candida spp. and the action mechanism. Methods: We used broth microdilution assays to determine the MIC, checkerboard assays to investigate synergism, and flow cytometry and molecular docking tests to ascertain action mechanism. Results: Hydralazine alone had antifungal activity in the range of 16-128 μg/ml and synergistic effect with itraconazole versus 100% of the fungal isolates, while there was synergy with fluconazole against 11.11% of the isolates. There was molecular interaction with the receptors exo-B(1,3)-glucanase and CYP51, causing reduced cell viability and DNA damage. Conclusion: Hydralazine is synergistic with itraconazole and triggers cell death of Candida spp. at low concentrations, demonstrating antifungal potential.

AFM evaluation of a humanized recombinant antibody affecting C. auris cell wall and stability

Fungal infections are increasingly impacting on the health of the population and particularly on subjects with a compromised immune system. The resistance phenomenon and the rise of new species carrying sometimes intrinsic and multi-drug resistance to the most commonly used antifungal drugs are greatly concerning healthcare organizations. As a result of this situation, there is growing interest in the development of therapeutic agents against pathogenic fungi. In particular, the Candida genus is responsible for severe life-threatening infections and among its species, C. auris is considered an urgent threat by the Center for Disease Control and Prevention, and is one of the three leading causes of morbidity and mortality worldwide. H5K1 is a humanized monoclonal antibody (hmAb) that selectively binds to β-1,3-glucans, vital components of the fungal cell wall. It has been previously demonstrated that it is active against Candida species, especially against C. auris, reaching its greatest potential when combined with commercially available antifungal drugs. Here we used atomic force microscopy (AFM) to assess the effects of H5K1, alone and in combination with fluconazole, caspofungin and amphotericin B, on C. auris cells. Through an extensive exploration we found that H5K1 has a significant role in the perturbation and remodeling of the fungal cell wall that is reflected in the loss of whole cell integrity. Moreover, it contributes substantially to the alterations in terms of chemical composition, stiffness and roughness induced specifically by caspofungin and amphotericin B. In addition to this, we demonstrated that AFM is a valuable technique to evaluate drug-microorganism interaction.

Modulation of the nanoscale motion rate of Candida albicans by X-rays

Introduction

Patients undergoing cancer treatment by radiation therapy commonly develop Candida albicans infections (candidiasis). Such infections are generally treated by antifungals that unfortunately also induce numerous secondary effects in the patient. Additional to the effect on the immune system, ionizing radiation influences the vital activity of C. albicans cells themselves; however, the reaction of C. albicans to ionizing radiation acting simultaneously with antifungals is much less well documented. In this study, we explored the effects of ionizing radiation and an antifungal drug and their combined effect on C. albicans.

Methods

The study essentially relied on a novel technique, referred to as optical nanomotion detection (ONMD) that monitors the viability and metabolic activity of the yeast cells in a label and attachment-free manner.

Results and discussion

Our findings demonstrate that after exposure to X-ray radiation alone or in combination with fluconazole, low-frequency nanoscale oscillations of whole cells are suppressed and the nanomotion rate depends on the phase of the cell cycle, absorbed dose, fluconazole concentration, and post-irradiation period. In a further development, the ONMD method can help in rapidly determining the sensitivity of C. albicans to antifungals and the individual concentration of antifungals in cancer patients undergoing radiation therapy.

Lycopene, Mesoporous Silica Nanoparticles and Their Association: A Possible Alternative against Vulvovaginal Candidiasis?

Commonly found colonizing the human microbiota, Candida albicans is a microorganism known for its ability to cause infections, mainly in the vulvovaginal region known as vulvovaginal candidiasis (VVC). This pathology is, in fact, one of the main C. albicans clinical manifestations, changing from a colonizer to a pathogen. The increase in VVC cases and limited antifungal therapy make C. albicans an increasingly frequent risk in women's lives, especially in immunocompromised patients, pregnant women and the elderly. Therefore, it is necessary to develop new therapeutic options, especially those involving natural products associated with nanotechnology, such as lycopene and mesoporous silica nanoparticles. From this perspective, this study sought to assess whether lycopene, mesoporous silica nanoparticles and their combination would be an attractive product for the treatment of this serious disease through microbiological in vitro tests and acute toxicity tests in an alternative in vivo model of Galleria mellonella. Although they did not show desirable antifungal activity for VVC therapy, the present study strongly encourages the use of mesoporous silica nanoparticles impregnated with lycopene for the treatment of other human pathologies, since the products evaluated here did not show toxicity in the in vivo test performed, being therefore, a topic to be further explored.

The Antibiofilm Role of Biotics Family in Vaginal Fungal Infections

“Unity in strength” is a notion that can be exploited to characterize biofilms as they bestow microbes with protection to live freely, escalate their virulence, confer high resistance to therapeutic agents, and provide active grounds for the production of biofilms after dispersal. Naturally, fungal biofilms are inherently resistant to many conventional antifungals, possibly owing to virulence factors as their ammunitions that persistently express amid planktonic transition to matured biofilm state. These ammunitions include the ability to form polymicrobial biofilms, emergence of persister cells post-antifungal treatment and acquisition of resistance genes. One of the major disorders affecting vaginal health is vulvovaginal candidiasis (VVC) and its reoccurrence is termed recurrent VVC (RVVC). It is caused by the Candida species which include Candida albicans and Candida glabrata. The aforementioned Candida species, notably C. albicans is a biofilm producing pathogen and habitually forms part of the vaginal microbiota of healthy women. Latest research has implicated the role of fungal biofilms in VVC, particularly in the setting of treatment failure and RVVC. Consequently, a plethora of studies have advocated the utilization of probiotics in addressing these infections. Specifically, the excreted or released compounds of probiotics which are also known as postbiotics are being actively researched with vast potential to be used as therapeutic options for the treatment and prevention of VVC and RVVC. These potential sources of postbiotics are harnessed due to their proven antifungal and antibiofilm. Hence, this review discusses the role of Candida biofilm formation in VVC and RVVC. In addition, we discuss the application of pro-, pre-, post-, and synbiotics either individually or in combined regimen to counteract the abovementioned problems. A clear understanding of the role of biofilms in VVC and RVVC will provide proper footing for further research in devising novel remedies for prevention and treatment of vaginal fungal infections.

Disruption of Iron Homeostasis and Mitochondrial Metabolism Are Promising Targets to Inhibit Candida auris

Fungal infections are a global threat, but treatments are limited due to a paucity in antifungal drug targets and the emergence of drug-resistant fungi such as Candida auris. Metabolic adaptations enable microbial growth in nutrient-scarce host niches, and they further control immune responses to pathogens, thereby offering opportunities for therapeutic targeting. Because it is a relatively new pathogen, little is known about the metabolic requirements for C. auris growth and its adaptations to counter host defenses. Here, we establish that triggering metabolic dysfunction is a promising strategy against C. auris. Treatment with pyrvinium pamoate (PP) induced metabolic reprogramming and mitochondrial dysfunction evident in disrupted mitochondrial morphology and reduced tricarboxylic acid (TCA) cycle enzyme activity. PP also induced changes consistent with disrupted iron homeostasis. Nutrient supplementation experiments support the proposition that PP-induced metabolic dysfunction is driven by disrupted iron homeostasis, which compromises carbon and lipid metabolism and mitochondria. PP inhibited C. auris replication in macrophages, which is a relevant host niche for this yeast pathogen. We propose that PP causes a multipronged metabolic hit to C. auris: it restricts the micronutrient iron to potentiate nutritional immunity imposed by immune cells, and it further causes metabolic dysfunction that compromises the utilization of macronutrients, thereby curbing the metabolic plasticity needed for growth in host environments. Our study offers a new avenue for therapeutic development against drug-resistant C. auris, shows how complex metabolic dysfunction can be caused by a single compound triggering antifungal inhibition, and provides insights into the metabolic needs of C. auris in immune cell environments. IMPORTANCE Over the last decade, Candida auris has emerged as a human pathogen around the world causing life-threatening infections with wide-spread antifungal drug resistance, including pandrug resistance in some cases. In this study, we addressed the mechanism of action of the antiparasitic drug pyrvinium pamoate against C. auris and show how metabolism could be inhibited to curb C. auris proliferation. We show that pyrvinium pamoate triggers sweeping metabolic and mitochondrial changes and disrupts iron homeostasis. PP-induced metabolic dysfunction compromises the utilization of both micro- and macronutrients by C. auris and reduces its growth in vitro and in immune phagocytes. Our findings provide insights into the metabolic requirements for C. auris growth and define the mechanisms of action of pyrvinium pamoate against C. auris, demonstrating how this compound works by inhibiting the metabolic flexibility of the pathogen. As such, our study characterizes credible avenues for new antifungal approaches against C. auris.

A Cecropin-4 Derived Peptide C18 Inhibits Candida albicans by Disturbing Mitochondrial Function

Global burden of fungal infections and related health risk has accelerated at an incredible pace, and multidrug resistance emergency aggravates the need for the development of new effective strategies. Candida albicans is clinically the most ubiquitous pathogenic fungus that leads to high incidence and mortality in immunocompromised patients. Antimicrobial peptides (AMPs), in this context, represent promising alternatives having potential to be exploited for improving human health. In our previous studies, a Cecropin-4-derived peptide named C18 was found to possess a broader antibacterial spectrum after modification and exhibit significant antifungal activity against C. albicans. In this study, C18 shows antifungal activity against C. albicans or non-albicans Candida species with a minimum inhibitory concentration (MIC) at 4∼32 μg/ml, and clinical isolates of fluconazole (FLZ)-resistance C. tropicalis were highly susceptible to C18 with MIC value of 8 or 16 μg/ml. Additionally, C18 is superior to FLZ for killing planktonic C. albicans from inhibitory and killing kinetic curves. Moreover, C18 could attenuate the virulence of C. albicans, which includes damaging the cell structure, retarding hyphae transition, and inhibiting biofilm formation. Intriguingly, in the Galleria mellonella model with C. albicans infection, C18 could improve the survival rate of G. mellonella larvae to 70% and reduce C. albicans load from 5.01 × 107 to 5.62 × 104 CFU. For mechanistic action of C18, the level of reactive oxygen species (ROS) generation and cytosolic Ca2 + increased in the presence of C18, which is closely associated with mitochondrial dysfunction. Meanwhile, mitochondrial membrane potential (△Ψm) loss and ATP depletion of C. albicans occurred with the treatment of C18. We hypothesized that C18 might inhibit C. albicans via triggering mitochondrial dysfunction driven by ROS generation and Ca2 + accumulation. Our observation provides a basis for future research to explore the antifungal strategies and presents C18 as an attractive therapeutic candidate to be developed to treat candidiasis.

Drug-dependent growth curve reshaping reveals mechanisms of antifungal resistance in Saccharomyces cerevisiae

Microbial drug resistance is an emerging global challenge. Current drug resistance assays tend to be simplistic, ignoring complexities of resistance manifestations and mechanisms, such as multicellularity. Here, we characterize multicellular and molecular sources of drug resistance upon deleting the AMN1 gene responsible for clumping multicellularity in a budding yeast strain, causing it to become unicellular. Computational analysis of growth curve changes upon drug treatment indicates that the unicellular strain is more sensitive to four common antifungals. Quantitative models uncover entwined multicellular and molecular processes underlying these differences in sensitivity and suggest AMN1 as an antifungal target in clumping pathogenic yeasts. Similar experimental and mathematical modeling pipelines could reveal multicellular and molecular drug resistance mechanisms, leading to more effective treatments against various microbial infections and possibly even cancers.

Combined growth curve experiments and quantitative modeling reveal antifungal responses of planktonic yeast, providing a future framework to examine antimicrobial drug resistance.

Extending the Proteomic Characterization of Candida albicans Exposed to Stress and Apoptotic Inducers through Data-Independent Acquisition Mass Spectrometry

Candida albicans is a commensal fungus that causes systemic infections in immunosuppressed patients. In order to deal with the changing environment during commensalism or infection, C. albicans must reprogram its proteome. Characterizing the stress-induced changes in the proteome that C. albicans uses to survive should be very useful in the development of new antifungal drugs. We studied the C. albicans global proteome after exposure to hydrogen peroxide (H₂O₂) and acetic acid (AA), using a data-independent acquisition mass spectrometry (DIA-MS) strategy. More than 2,000 C. albicans proteins were quantified using an ion library previously constructed using data-dependent acquisition mass spectrometry (DDA-MS). C. albicans responded to treatment with H₂O₂ with an increase in the abundance of many proteins involved in the oxidative stress response, protein folding, and proteasome-dependent catabolism, which led to increased proteasome activity. The data revealed a previously unknown key role for Prn1, a protein similar to pirins, in the oxidative stress response. Treatment with AA resulted in a general decrease in the abundance of proteins involved in amino acid biosynthesis, protein folding, and rRNA processing. Almost all proteasome proteins declined, as did proteasome activity. Apoptosis was observed after treatment with H₂O₂ but not AA. A targeted proteomic study of 32 proteins related to apoptosis in yeast supported the results obtained by DIA-MS and allowed the creation of an efficient method to quantify relevant proteins after treatment with stressors (H₂O₂, AA, and amphotericin B). This approach also uncovered a main role for Oye32, an oxidoreductase, suggesting this protein as a possible apoptotic marker common to many stressors.

IMPORTANCE Fungal infections are a worldwide health problem, especially in immunocompromised patients and patients with chronic disorders. Invasive candidiasis, caused mainly by C. albicans, is among the most common fungal diseases. Despite the existence of treatments to combat candidiasis, the spectrum of drugs available is limited. For the discovery of new drug targets, it is essential to know the pathogen response to different stress conditions. Our study provides a global vision of proteomic remodeling in C. albicans after exposure to different agents, such as hydrogen peroxide, acetic acid, and amphotericin B, that can cause apoptotic cell death. These results revealed the significance of many proteins related to oxidative stress response and proteasome activity, among others. Of note, the discovery of Prn1 as a key protein in the defense against oxidative stress as well the increase in the abundance of Oye32 protein when apoptotic process occurred point them out as possible drug targets.

A Systematic Survey of Characteristic Features of Yeast Cell Death Triggered by External Factors

Cell death in response to distinct stimuli can manifest different morphological traits. It also depends on various cell death signaling pathways, extensively characterized in higher eukaryotes but less so in microorganisms. The study of cell death in yeast, and specifically Saccharomyces cerevisiae, can potentially be productive for understanding cell death, since numerous killing stimuli have been characterized for this organism. Here, we systematized the literature on external treatments that kill yeast, and which contains at least minimal data on cell death mechanisms. Data from 707 papers from the 7000 obtained using keyword searches were used to create a reference table for filtering types of cell death according to commonly assayed parameters. This table provides a resource for orientation within the literature; however, it also highlights that the common view of similarity between non-necrotic death in yeast and apoptosis in mammals has not provided sufficient progress to create a clear classification of cell death types. Differences in experimental setups also prevent direct comparison between different stimuli. Thus, side-by-side comparisons of various cell death-inducing stimuli under comparable conditions using existing and novel markers that can differentiate between types of cell death seem like a promising direction for future studies.

β-amyrin-induced apoptosis in Candida albicans triggered by calcium

The emergence of drug-resistant pathogens has urged researchers to discover alternatives for traditional antibiotics. β-amyrin, which is included in the category of triterpenoids extracted from plants, is known for its antimicrobial activity, although the underlying mechanism has not yet been revealed. This study was conducted to elucidate the antifungal mode of action of β-amyrin against Candida albicans. Based on the relevance between triterpenoids and oxidative molecules, reactive oxygen species (ROS) concentrations were detected, which showed a noticeable increment. Disruption of Ca²⁺ homeostasis in the cytosol was additionally analyzed, which was supported by interactions between two. Subsequently, decrease in mitochondrial membrane potential, increment of mitochondrial Ca²⁺, and ROS concentration were monitored, which suggested mitochondrial dysfunction modulated by Ca²⁺. Further investigation confirmed oxidative damage through glutathione reduction and DNA fragmentation. Accumulation of lethal damages resulted in the activation of caspases and externalization of phosphatidylserine, indicating the induction of yeast apoptosis by β-amyrin in C. albicans.

Azole-triphenylphosphonium conjugates combat antifungal resistance and alleviate the development of drug-resistance

Azole antifungals are commonly used to treat fungal infections but have resulted in the occurrence of drug resistance. Therefore, developing azole derivatives (AZDs) that can both combat established drug-resistant fungal strains and evade drug resistance is of great importance. In this study, we synthesized a series of AZDs with a fluconazole (FLC) skeleton conjugated with a mitochondria-targeting triphenylphosphonium cation (TPP⁺). These AZDs displayed potent activity against both azole-sensitive and azole-resistant Candida strains without eliciting obvious resistance. Moreover, two representative AZDs, 20 and 25, exerted synergistic antifungal activity with Hsp90 inhibitors against C. albicans strains resistant to the combination treatment of FLC and Hsp90 inhibitors. AZD 25, which had minimal cytotoxicity, was effective in preventing C. albicans biofilm formation. Mechanistic investigation revealed that AZD 25 inhibited the biosynthesis of the fungal membrane component ergosterol and interfered with mitochondrial function. Our findings provide an alternative approach to address fungal resistance problems.

Proteomic changes in Trypanosoma cruzi epimastigotes treated with the proapoptotic compound PAC-1

Apoptosis is a highly regulated process of cell death in metazoans. Therefore, understanding the biochemical changes associated with apoptosis-like death in Trypanosoma cruzi is key to drug development. PAC-1 was recently shown to induce apoptosis in T. cruzi; with this as motivation, we used quantitative proteomics to unveil alterations of PAC-1-treated versus untreated epimastigotes. The PAC-1 treatment reduced the abundance of putative vesicle-associated membrane protein, putative eukaryotic translation initiation factor 1 eIF1, coatomer subunit beta, putative amastin, and a putative cytoskeleton-associated protein. Apoptosis-like signaling also increases the abundance of proteins associated with actin cytoskeleton remodeling, cell polarization, apoptotic signaling, phosphorylation, methylation, ergosterol biosynthesis, vacuolar proteins associated with autophagy, and flagellum motility. We shortlist seventeen protein targets for possible use in chemotherapy for Chagas disease. Almost all differentially abundant proteins belong to a family of proteins previously associated with apoptosis in metazoans, suggesting that the apoptotic pathway's key functions have been preserved from trypanosomatids and metazoans. SIGNIFICANCE: Approximately 8 million people worldwide are infected with Trypanosoma cruzi. The treatment of Chagas disease comprises drugs with severe side effects, thus limiting their application. Thus, developing new pharmaceutical solutions is relevant, and several molecules targeting apoptosis are therapeutically efficient for parasitic, cardiac, and neurological diseases. Apoptotic processes lead to specific morphological features that have been previously observed in T. cruzi. Here, we investigate changes in epimastigotes' proteomic profile treated with the proapoptotic compound PAC-1, providing data concerning the regulation of both metabolic and cellular processes in nonmetazoan apoptotic cells. We shortlist seventeen protein target candidates for use in chemotherapy for Chagas disease.

Succinyl chitosan gold nanocomposite: Preparation, characterization, in vitro and in vivo anticandidal activity

Herein, we have successfully synthesized a novel N-Succinyl chitosan/gold nanocomposite (N-SuC/Au NC) using N-SuC and gold(III) chloride, and investigated the biocompatibility and antifungal activity. The synthesized N-SuC/Au NC was characterized by UV-visible spectroscopy, X-ray diffraction, field emission scanning electron microscope, and inductively coupled plasma atomic emission spectroscopy. The N-SuC/Au NC exhibited a strong inhibition effect towards pathogenic Candida albicans. Morphological analysis revealed the destruction of C. albicans cell membrane due to N-SuC/Au NC treatment. The in vitro and in vivo toxicity of N-SuC/Au NC was analyzed with HEK293T mammalian cells and zebrafish larvae, respectively. The synthesized N-SuC/Au NC demonstrated no cytotoxicity towards HEK293T cells up to 1200 μg/mL concentration. The survival rate of the zebrafish larvae at 120 hpf, was found as 100% up to 1200 μg/mL of N-SuC/Au NC exposure. The in vivo studies further confirmed the inhibitory effects of N-SuC/Au NC on the formation of C. albicans hyphae in infected zebrafish muscle tissue.

In vivo Activity of Copper(II), Manganese(II), and Silver(I) 1,10-Phenanthroline Chelates Against Candida haemulonii Using the Galleria mellonella Model

Candida haemulonii is an emerging opportunistic pathogen resistant to most antifungal drugs currently used in clinical arena. Metal complexes containing 1,10-phenanthroline (phen) chelating ligands have well-established anti-Candida activity against different medically relevant species. This study utilized larvae of Galleria mellonella, a widely used model of in vivo infection, to examine C. haemulonii infection characteristics in response to different copper(II), manganese(II), and silver(I) chelates containing phen, which had demonstrated potent anti-C. haemulonii activity in a previous study. The results showed that C. haemulonii virulence was influenced by inoculum size and incubation temperature, and the host G. mellonella immune response was triggered in an inoculum-dependent manner reflected by the number of circulating immune cells (hemocytes) and observance of larval melanization process. All test chelates were non-toxic to the host in concentrations up to 10 μg/larva. The complexes also affected the G. mellonella immune system, affecting the hemocyte number and the expression of genes encoding antifungal and immune-related peptides (e.g., inducible metalloproteinase inhibitor protein, transferrin, galiomycin, and gallerimycin). Except for [Ag₂(3,6,9-tdda)(phen)₄].EtOH (3,6,9-tddaH₂ = 3,6,9-trioxoundecanedioic acid), all chelates were capable of affecting the fungal burden of infected larvae and the virulence of C. haemulonii in a dose-dependent manner. This work shows that copper(II), manganese(II), and silver(I) chelates containing phen with anti-C. haemulonii activity are capable of (i) inhibiting fungal proliferation during in vivo infection, (ii) priming an immune response in the G. mellonella host and (iii) affecting C. haemulonii virulence.

Octominin: A Novel Synthetic Anticandidal Peptide Derived from Defense Protein of Octopus minor

The rapid emergence of multidrug-resistant pathogens makes an urgent need for discovering novel antimicrobial agents as alternatives to conventional antibiotics. Towards this end, we designed and synthesized a synthetic peptide of 23 amino acids (AAs) (¹GWLIRGAIHAGKAIHGLIHRRRH²³) from a defense protein 3 cDNA sequence of Octopus minor. The sequence of the peptide, which was named Octominin, had characteristic features of known antimicrobial peptides (AMPs) such as a positive charge (+5), high hydrophobic residue ratio (43%), and 1.86 kcal/mol of Boman index. Octominin was predicted to have an alpha-helix secondary structure. The synthesized Octominin was 2625.2 Da with 92.5% purity. The peptide showed a minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of 50 and 200 μg/mL, respectively, against Candida albicans. Field emission scanning electron microscopy observation confirmed that Octominin caused ultrastructural cell wall deformities in C. albicans. In addition, propidium iodide penetrated the Octominin-treated C. albicans cells, further demonstrating loss of cell membrane integrity that caused cell death at both MIC and MFC. Octominin treatment increased the production of intracellular reactive oxygen species and decreased cell viability in a concentration dependent manner. Cytotoxicity assays revealed no significant influence of Octominin on the viability of human embryonic kidney 293T cell line, with over 95% live cells in the Octominin-treated group observed up to 100 µg/mL. Moreover, we confirmed the antifungal action of Octominin in vivo using a zebrafish experimental infection model. Overall, our results demonstrate the Octominin is a lead compound for further studies, which exerts its effects by inducing cell wall damage, causing loss of cell membrane integrity, and elevating oxidative stress.

Chloroacetamide derivatives as a promising topical treatment for fungal skin infections

The aim of this study was to evaluate the antifungal potential of 11 chloroacetamide derivatives and derivative incorporated into a film-forming system (FFS) as a potential alternative for the topical treatment of superficial and skin mycoses. The minimum inhibitory concentration (MIC) evaluation followed Clinical and Laboratory Standards Institute protocols M27-A3 (Candida) and M28-A2 (dermatophytes). Compounds 2, 3, and 4 were the most effective against Candida species (MIC range: 25-50 µg/mL) and dermatophytes (MIC range: 3.12-50 µg/mL). Compound 2 maintained its antifungal activity when incorporated in a FFS, with MIC values equivalent to the free compound. In addition, the compound does not act through complexation with ergosterol, suggesting that it may act on other targets of the fungal cell membrane. Chloroacetamide derivatives presented anti-Candida and anti-dermatophytic effectiveness. The FFS containing compound 2 has shown to be superior to traditional topical treatment of superficial and cutaneous fungal infections. It was found that these new chemical entities, with their applicability, are an excellent alternative to the topical treatment of fungal skin infections.

Combined systemic (fluconazole) and topical (metronidazole + clotrimazole) therapy for a new approach to the treatment and prophylaxis of recurrent candidiasis

Recurrent vulvovaginal candidiasis (RVVC) is an important pathological and infectious condition that can greatly impact a woman's health and quality of life. Clinical and epidemiological studies show that different types of therapies are able to eliminate the signs and symptoms of mycotic vaginitis in the acute phase, but so far none of these has proved able to significantly reduce the risk of long-term recurrence. In this review, based on the available literature and original data from a preliminary in-vitro microbiological study on the compatibility between fluconazole, clotrimazole and metronidazole a new therapeutic approach to RVVC is discussed and presented. The treatment proposed is a combined scheme using both systemic antimicrobial drug therapy with oral fluconazole 200 mg and topical drug therapy using the association metronidazole 500 mg and clotrimazole 100 mg (vaginal ovules) with adjuvant oral probiotic therapy. In detail, at the time of diagnosis in the acute symptom phase, we propose the following treatment scheme: fluconazole 200 mg on day 1, 4, 11, 26, then 1 dose/month for 3 months at the end of the menstrual cycle; plus metronidazole/clotrimazole ovules 1/day for 6 days the first week, then 1 ovule/day for 3 days the week before the menstrual cycle for 3 months; plus probiotic 1 dose/day for 10 days for 3 months starting from the second month to the end of the menstrual cycle. This scheme aims to address the recurrent infection aggressively from the outset by attempting not only to treat acute symptoms, but also to prevent a new event by countering many of the potential risk factors of recurrence, such as the intestinal Candida reservoir, the mycotic biorhythm, the formation of biofilm, the phenotype switching and the presence of infections complicated by the presence of C. non albicans or G. Vaginalis, without interfering, but rather favoring the restoration of the vaginal lactobacillus species. Future clinical studies will be useful to confirm the proposed scheme.

Electrochemical Response of Saccharomyces cerevisiae Corresponds to Cell Viability upon Exposure to Dioclea reflexa Seed Extracts and Antifungal Drugs

Dioclea reflexa bioactive compounds have been shown to contain antioxidant properties. The extracts from the same plant are used in traditional medical practices to treat various diseases with impressive outcomes. In this study, ionic mobility in Saccharomyces cerevisiae cells in the presence of D. reflexa seed extracts was monitored using electrochemical detection methods to link cell death to ionic imbalance. Cells treated with ethanol, methanol, and water extracts were studied using cyclic voltammetry and cell counting to correlate electrochemical behavior and cell viability, respectively. The results were compared with cells treated with pore-forming Amphotericin b (Amp b), as well as Fluconazole (Flu) and the antimicrobial drug Rifampicin (Rif). The D. reflexa seed water extract (SWE) revealed higher anodic peak current with 58% cell death. Seed methanol extract (SME) and seed ethanol extract (SEE) recorded 31% and 22% cell death, respectively. Among the three control drugs, Flu revealed the highest cell death of about 64%, whereas Amp b and Rif exhibited cell deaths of 35% and 16%, respectively, after 8 h of cell growth. It was observed that similar to SWE, there was an increase in the anodic peak current in the presence of different concentrations of Amp b, which also correlated with enhanced cell death. It was concluded from this observation that Amp b and SWE might follow similar mechanisms to inhibit cell growth. Thus, the individual bioactive compounds from the water extracts of D. reflexa seeds could further be purified and tested to validate their potential therapeutic application. The strategy to link electrochemical behavior to biochemical responses could be a simple, fast, and robust screening technique for new drug targets and to understand the mechanism of action of such drugs against disease models.

Cytotoxic and Genotoxic Effects of Fluconazole on African Green Monkey Kidney (Vero) Cell Line

Fluconazole is a broad-spectrum triazole antifungal that is well-established as the first-line treatment for Candida albicans infections. Despite its extensive use, reports on its genotoxic/mutagenic effects are controversial; therefore, further studies are needed to better clarify such effects. African green monkey kidney (Vero) cells were exposed in vitro to different concentrations of fluconazole and were then evaluated for different parameters, such as cytotoxicity (MTT/cell death by fluorescent dyes), genotoxicity/mutagenicity (comet assay/micronucleus test), and induction of oxidative stress (DCFH-DA assay). Fluconazole was used at concentrations of 81.6, 163.2, 326.5, 653, 1306, and 2612.1μM for the MTT assay and 81.6, 326.5, and 1306μM for the remaining assays. MTT results showed that cell viability reduced upon exposure to fluconazole concentration of 1306μM (85.93%), being statistically significant (P<0.05) at fluconazole concentration of 2612.1μM (35.25%), as compared with the control (100%). Fluconazole also induced necrosis (P<0.05) in Vero cell line when cells were exposed to all concentrations (81.6, 326.5, and 1306μM) for both tested harvest times (24 and 48 h) as compared with the negative control. Regarding genotoxicity/mutagenicity, results showed fluconazole to increase significantly (P<0.05) DNA damage index, as assessed by comet assay, at 1306μM versus the negative control (DI=1.17 vs DI=0.28, respectively). Micronucleus frequency also increased until reaching statistical significance (P<0.05) at 1306μM fluconazole (with 42MN/1000 binucleated cells) as compared to the negative control (13MN/1000 binucleated cells). Finally, significant formation of reactive oxygen species (P<0.05) was observed at 1306μM fluconazole vs the negative control (OD=40.9 vs OD=32.3, respectively). Our experiments showed that fluconazole is cytotoxic and genotoxic in the assessed conditions. It is likely that such effects may be due to the oxidative properties of fluconazole and/or the presence of FMO (flavin-containing monooxygenase) in Vero cells.