Growth of Candida albicans hyphae

Antifungal Activity of Electrochemically Etched Nanotextured Stainless Steel against Candida albicans and Fusarium oxysporum Fungal Cells

Fungal adhesion to stainless steel, an alloy commonly used in the food and beverage sectors, public and healthcare settings, and numerous medical devices, can give rise to serious infections, ultimately leading to morbidity, mortality, and significant healthcare expenses. In this study, we demonstrate that nanotextured stainless steel (nSS) fabricated using an electrochemical technique is an antibiotic-free biocidal surface against Candida albicans and Fusarium oxysporum fungal cells with 98% and 97% reduction, respectively. The nanoprotrusion features on nSS can have both physical contact with cell membranes and a chemical impact on cells through the production of reactive species; this material should not contribute to drug-resistant fungus as antibiotics can. As nSS is also antibacterial and compatible with mammalian cells, the demonstration of antifungal activity gives nSS the potential to be used to create effective, scalable, and sustainable solutions to broadly and responsibly prevent fungal and other microbial infections caused by surface contamination.

PPI network identifies interacting pathogenic signaling pathways in Candida albicans

Candida albicans, an opportunistic and systemic infection causing fungus, causes skin, nail, and mucosal layer lesions in healthy individuals and hospital borne catheter-related and nosocomial infections. This particular fungus exists in two distinct stages in its life cycle: yeast and hyphae. In this study, 20 signaling pathways associated with 177 proteins from C. albicans were identified to construct a PPI network. The core part of the network consisted of 165 proteins. Network topology analyses revealed that the formed PPI network is biologically robust and scale-free, with significant interactions between proteins through 19 252 shortest pathways. In this network, the top 10 hub proteins (RAS1, CDC42, HOG1, CPH1, STE11, EFG1, CEK1, HSP90, TEC1 and CST20) were identified using network analysis, which seem to be the most important proteins involved in different pathways for the development of pathogenesis and virulence. Modular analysis of the network resulted in top six sub-networks, three of which shared eight hub proteins. Ontology and functional enrichment analyses revealed that the majority of the proteins were associated with regulation of transcription by RNA polymerase II, plasma membrane and nucleic acid binding in biological processes, and cellular components and molecular functions, respectively. Enrichment analysis indicated that the proteins were mostly involved in oxidative phosphorylation and purine metabolism signaling pathways. We determined the complex web of signaling pathway involving proteins via PPI network analysis to unravel and decipher protein interactions within C. albicans to understand the complex pathogenesis processes for targeted therapeutic interferences using novel bioinformatics strategies.

Antifungal Effect of Poly(methyl methacrylate) Coated with Polyelectrolyte Multilayers

Due to teeth loss, a large proportion of the elderly rely on full or partial dentures for esthetic, speaking, and eating reasons. A variety of polymers are used in the production of removable prostheses, with poly-(methyl methacrylate) (PMMA) being a widely used material for making denture bases. However, underdenture stomatitis caused by the fungi Candida albicans is still an open problem. The purpose of this work was to consider the impact of polyelectrolyte multilayer (PEM) coating on PMMA surfaces and the effect of the addition of sucrose on the adhesion properties of C. albicans. Two polyelectrolytes were applied for the formation of the PEM coating: poly-(allylamine) hydrochloride (PAH) and poly-(acrylic) acid (PAA). The uncoated and coated surfaces were characterized in terms of topography, surface potential, and hydrophobicity. The extent of adhesion of C. albicans to the surfaces was assessed by scanning electron microscopy. Results show that surfaces coated with negatively charged PAA as the PEM terminating layer adhere less C. albicans than uncoated PMMA or surfaces coated with positively charged PAH as the PEM terminating layer. The addition of sucrose increases the fungal adhesion extent of C. albicans to both types of coated surfaces, lowering the PAA antiadhesion properties. With the addition of sucrose, we were trying to mimic the impact of dentures on patients with a sugar-rich diet.

Transcriptional control of C. albicans white-opaque switching and modulation by environmental cues and strain background

The opportunistic fungal pathogen Candida albicans can undergo cellular transitions in response to environmental cues that impact its lifestyle and its interactions with the human host. This is exemplified by the white-opaque switch, which is a heritable transition between two phenotypic states that is regulated by a highly interconnected network of transcription factors (TFs). To obtain greater understanding of the transcriptional regulation of the switch, we generated a genome-wide, tetracycline-inducible TF library in the WO-1 strain background and identified those TFs whose forced expression induces white cells to switch to the opaque state. This set of opaque-inducing TFs was also evaluated for their ability to induce switching in a second strain background, that of the standard reference strain SC5314, as well as during growth on different laboratory media. These experiments identify 14 TFs that can drive white-to-opaque switching when overexpressed but that do so in a highly strain- and media-specific manner. In particular, changes in pH, amino acids, and zinc concentrations had marked effects on the ability of TFs to drive phenotypic switching. These results provide insights into the complex transcriptional regulation of switching in C. albicans and reveal that an interplay between genetic and environmental factors determines TF function and cell fate.IMPORTANCEThe white-opaque switch in Candida albicans represents a model system for understanding an epigenetic switch in a eukaryotic pathogen. Here, we generated an inducible library of the set of transcription factors (TFs) present in C. albicans and identify 14 TFs that can drive the white-to-opaque transition when ectopically expressed. We demonstrate that several of these TFs induce the switch in a highly strain- and media-specific manner. This highlights that both strain background and changes in experimental conditions (including different water sources) can profoundly impact the phenotypic consequences of TF overexpression. Moreover, the inducible TF library provides an invaluable tool for the further analysis of TF function in this important human pathogen.

Endocytosis in filamentous Fungi: Coordinating polarized hyphal growth and membrane recycling

Filamentous fungi rely on a finely tuned balance between exocytosis and endocytosis to maintain polarized growth. This review highlights the essential role of the subapical endocytic collar in recycling excess plasma membrane and key proteins, enabling sustained hyphal extension. It distinguishes between clathrin-mediated and AP-2-dependent clathrin-independent pathways, emphasizing their unique contributions to membrane homeostasis and cargo trafficking. The synthesis of quantitative imaging and genetic analyses provides a comprehensive framework for understanding vesicle dynamics, with implications for addressing fungal pathogenicity and industrial applications.

Candidalysin biology and activation of host cells

Candida albicans is an opportunistic fungal pathogen that can cause life-threatening systemic infections and distressing mucosal infections. A major breakthrough in understanding C. albicans pathogenicity was the discovery of candidalysin, the first cytolytic peptide toxin identified in a human pathogenic fungus. Secreted by C. albicans hyphae and encoded by the ECE1 gene, this 31-amino acid peptide integrates into and permeabilizes host cell membranes, causing damage across diverse cell types. Beyond its cytolytic activity, candidalysin can trigger potent innate immune responses in epithelial cells, macrophages, and neutrophils. Additionally, candidalysin plays a key role in nutrient acquisition during infection. This review explores the biology of candidalysin, its role in host cell activation, and extends the discussion to non-candidalysin Ece1p peptides, shedding light on their emerging significance.

Sustainable Antimicrobial and Anticancer Agents: Eco-Friendly Synthesis of Copper Nanoparticles Using Biebersteinia multifida DC

Biebersteinia multifida DC. is a wild therapeutic plant, traditionally used for various medicinal applications. The aim of the present study is to extract bioactive constituents from the plants' roots and synthesize copper nanoparticles (CuNPs). Ethanolic extraction of the plant's roots yielded 19 bioactive compounds, recognized through gas chromatography-mass spectroscopy (GC-MS), mainly including citraconic anhydride, γ-sitosterol, and 2-furancarboxaldehyde. The prepared CuNPs have been fully characterized. The biological activity evaluations revealed these CuNPs possess acceptable antibacterial and antifungal activities. Furthermore, the CuNPs displayed significant cytotoxic potency toward "4T1 breast cancer cells" while showing a relatively low cell death rate against the normal "HEK-293 kidney cell". In conclusion, our findings showed that the CuNPs can be synthesized from B. multifida roots with a simple, fast, and eco-friendly procedure. These CuNPs are efficient in antimicrobial and anticancer activities.

Commensalism and pathogenesis of Candida albicans at the mucosal interface

Fungi are important and often underestimated human pathogens. Infections with fungi mostly originate from the environment, from soil or airborne spores. By contrast, Candida albicans, one of the most common and clinically important fungal pathogens, permanently exists in the vast majority of healthy individuals as a member of the human mucosal microbiota. Only under certain circumstances will these commensals cause infections. However, although the pathogenic behaviour and disease manifestation of C. albicans have been at the centre of research for many years, its asymptomatic colonization of mucosal surfaces remains surprisingly understudied. In this Review, we discuss the interplay of the fungus, the host and the microbiome on the dualism of commensal and pathogenic life of C. albicans, and how commensal growth is controlled and permitted. We explore hypotheses that could explain how the mucosal environment shapes C. albicans adaptations to its commensal lifestyle, while still maintaining or even increasing its pathogenic potential.

Identification of chicken-derived antibodies targeting the Candida albicans Als3 protein

Candida albicans is a major opportunistic pathogen, responsible for nearly half of clinical candidemia cases. The rising prevalence of azole-resistant Candida species represents a significant clinical challenge, underscoring the urgent need for alternative therapeutic strategies. Monoclonal antibody-based therapies have emerged as a promising and cost-effective approach to combating Candida infections. Agglutinin-like sequence protein 3 (Als3), a key cell surface protein of C. albicans, plays a pivotal role in adherence and biofilm formation, both of which are essential for its pathogenesis. In this study, recombinant Als3 protein was purified and utilized to immunize chickens, resulting in the production of Als3-specific immunoglobulin Y (IgY) antibodies. Two single-chain variable fragment (scFv) antibody libraries were subsequently constructed using phage display technology, yielding transformant counts of 5.3 × 107 and 2.8 × 107, respectively. Phage-based enzyme-linked immunosorbent assay (ELISA) revealed enhanced signals following bio-panning, enabling the identification and sequence validation of three scFv antibodies. These scFv antibodies exhibited strong binding activities to Als3, as confirmed through ELISA and western blot analyses. Binding affinities were determined to be ~ 10⁻⁸ M via serial titration ELISA and competitive ELISA. Additionally, the selected scFv antibodies specifically recognized endogenous Als3 protein in C. albicans, as demonstrated by western blot and cell-based ELISA assays. In conclusion, this study successfully generated and characterized high-affinity scFv antibodies targeting Als3, which exhibited exceptional specificity and binding activity. These findings highlight their potential as promising immunotherapeutic candidates for the treatment of C. albicans infections. KEY POINTS: • The Als3 protein of C. albicans is a critical biomarker and therapeutic target • Chicken-derived scFv antibodies against Als3 were developed via phage display • The scFv antibodies showed strong binding to endogenous Als3 in C. albicans.

MNN45 is involved in Zcf31-mediated cell surface integrity and chitosan susceptibility in Candida albicans

Candida albicans is a major human fungal pathogen; however, limited antifungal agents, undesirable drug side effects, and ineffective prevention of drug-resistant strains have become serious problems. Chitosan is a nontoxic, biodegradable, and biocompatible linear polysaccharide made from the deacetylation of chitin. In this study, a ZCF31 putative transcription factor gene was selected from a previous mutant library screen, as zcf31Δ strains exhibited defective cell growth in response to chitosan. Furthermore, chitosan caused notable damage to zcf31Δ cells; however, ZCF31 expression was not significantly changed by chitosan, suggesting that zcf31Δ is sensitive to chitosan could be due to changes in the physical properties of C. albicans. Indeed, zcf31Δ cells displayed significant increases in cell wall thickness. Consistent with the previous study, zcf31Δ strains were resistant to calcofluor white but highly susceptible to SDS (sodium dodecyl sulfate). These results implied that chitosan mainly influences membrane function, as zcf31Δ strengthens the stress resistance of the fungal cell wall but lessens cell membrane function. Interestingly, this effect on the cell surface mechanics of the C. albicans zcf31Δ strains was not responsible for the virulence-associated function. RNA-seq analysis further revealed that six mannosyltransferase-related genes were upregulated in zcf31Δ. Although five mannosyltransferase-related mutant strains in the zcf31Δ background partially reduced the cell wall thickness, only zcf31Δ/mnn45Δ showed the recovery of chitosan resistance. Our findings suggest that Zcf31 mediates a delicate and complicated dynamic balance between the cell membrane and cell wall architectures through the mannosyltransferase genes in C. albicans, leading to altered chitosan susceptibility.

Blocking the shikimate pathway amplifies the impact of carvacrol on biofilm formation in Candida albicans

Candida albicans typically thrives in a commensal relationship with humans but is also an opportunistic fungal pathogen. As an opportunistic pathogen, C. albicans relies heavily on its ability to assimilate nutrients, for which it must compete with the host and other microorganisms. Amino acid biosynthesis, sensing, and uptake play pivotal roles in C. albicans growth and pathogenicity. C. albicans biosynthesizes aromatic amino acids and co-enzyme Q de novo through the shikimate pathway, including the Aro1, Aro2, and Aro7 enzymes, but also has amino acid transporters for uptake from the environment. Thus, antifungal approaches targeting aromatic amino acid biosynthesis must simultaneously inhibit amino acid biosynthesis and uptake. Herein, we investigate the plant-based antifungal, carvacrol, in conjunction with aromatic amino acid biosynthetic mutants, as a potential anti-candidal strategy. Growth of the WT, ARO2, and ARO7 strains were inhibited by 150 µg/mL carvacrol, whereas the ARO1 mutant was slightly more sensitive (with MIC 125 µg/mL). All repressed mutants exposed to carvacrol are partially rescued in the presence of para-aminobenzoic acid (PABA) (CoQ precursor), indicating that blocking the shikimate pathway impacts both aromatic amino acid and CoQ biosynthesis. Moreover, carvacrol at sublethal concentrations significantly inhibits ARO1 adhesion and hyphal formation, along with pre-attached and pre-formed hyphae, ultimately impacting biofilm metabolic activity and biomass accumulation and significantly reducing biofilm growth. In summary, carvacrol increases the sensitivity of C. albicans to ARO1 repression, with attenuated adhesion, hyphal formation, mycelial growth and biofilm formation, likely by blocking aromatic amino acid uptake.IMPORTANCEThe opportunistic pathogen Candida albicans remains the leading cause of candidemia and invasive candidiasis (IC), causing significant morbidity and mortality in immunocompromised patients. Our current arsenal of effective antifungal drugs is limited in number, mechanistic diversity, and efficacy, are cytotoxic and associated with antifungal resistance, necessitating the development of novel antifungals and combination therapies. Here, we show how simultaneously blocking the shikimate pathway, through ARO1 repression, and disrupting aromatic amino acid uptake by carvacrol prevent C. albicans biofilm formation. Thus, inhibitors of the Aro1 enzyme in combination with carvacrol are expected to shut down C. albicans biofilm formation and virulence.

Internal transcribed spacer sequencing to explore the intrinsic composition of fungal communities in fungal esophagitis

BACKGROUND

Fungal esophagitis (FE) is caused by fungal invasion of the esophageal mucosa. Under endoscopy, the esophageal mucosa shows edema, congestion, erosion, and ulceration, and bleeds easily when touched, and the surface of the mucosa is covered with small white spots like "bean curd residue". Clinical cases showing typical FE under endoscopic imaging but negative esophageal mucosal brush (referred to as suspected FE) have increased the difficulty and challenge of clinical diagnosis and treatment. At present, the esophageal fungal flora of suspected case has not been thoroughly studied.

AIM

To characterize the fungal flora in FE, suspected FE, and the esophageal normal controls (NCs), and to identify marker species to improve detection of FE.

METHODS

This was a case-control study. A total of 19 patients with FE, 16 with suspected FE, and 10 NCs were selected by endoscopy. The esophageal cell brush samples of each group were sequenced by internal transcribed spacer (ITS) 1 and analyzed by bioinformatics.

RESULTS

In FE and suspected FE patients, species richness, species diversity and species evenness, as measured by the Chao1 index, Shannon index and Pielou index, were lower than in the NCs, and the comparison between the FE and NCs was the most significant (P < 0.05). Compared with the NCs, the relative abundance of Candida in FE and suspected FE patients was significantly increased (P < 0.001), while the relative abundance of Yarrowia was significantly decreased (P < 0.05). Moreover, Yarrowia abundance in the FE group was significantly lower than in the NCs and suspected FE groups (P < 0.001). The area under the curve for Candida in FE and suspected FE patients was 99.5% (P < 0.05) and 81.3% (P < 0.05), respectively. Finally, compared with FE patients, the relative abundance of Ascomycota and Candida in the esophageal flora of suspected FE patients was decreased, while the relative abundance of Yarrowia, Thermomyces and Pichia was increased.

CONCLUSION

ITS showed that composition of the fungal community was similar in the FE and suspected FE groups. ITS can be used as an auxiliary diagnostic method for FE and provide a theoretical basis for follow-up diagnosis and treatment.

Bio-orthogonal Labeling of Chitin in Native Pathogenic Candida Species via the Chitin Scavenge Pathway

The fungal cell wall is essential for the integrity of the cell, providing strength and shape, as well as protection against environmental stimuli. For pathogenic fungi, the cell wall is also the initial point of contact with the host. Specific cell wall features such as hypha tails and smaller glycan components modulate a wide range of fungal interactions with the immune defenses. Here, a bio-orthogonal labeling method utilizing N-acetyl-glucosamine (NAG) probes is developed to fluorescently label native, pathogenic yeast via the chitin scavenging pathway. A panel of NAG probes was assembled, synthesized, and characterized for the ability to label the chitin in pathogenic yeast. Enzymatic data show that the native scavenging biosynthetic enzyme, Hxk1, is promiscuous, permitting the labeling of the native chitin biopolymer. This chitin labeling method was validated via the development of mass spectrometry protocols. When compared to the current available labeling systems for chitin, the probes do not affect the integrity of the cell wall and do not interrupt cell growth. Furthermore, the NAG probes enabled multiple "click" platforms across pathogenic Candida species including Candida albicans and Candida tropicalis. Budding and filamentous hyphal states were observed. The results indicate the probes' utility for in vivo study of the morphological, pathogenic switch, and visualization of growth patterns. Thus, the use of these probes in pathogenic Candida strains is ideal for a variety of future applications including strain specific antifungals, diagnostic tools, and immunomodulators.

Cholesterol-terminated cationic lipidated oligomers (CLOs) as a new class of antifungals

Infections caused by fungal pathogens are a global health problem, and have created an urgent need for new antimicrobial strategies. This report details the synthesis of lipidated 2-vinyl-4,4-dimethyl-5-oxazolone (VDM) oligomers via an optimized Cu(0)-mediated reversible-deactivation radical polymerization (RDRP) approach. Cholesterol-Br was used as an initiator to synthesize a library of oligo-VDM (degree of polymerisation = 5, 10, 15, 20, and 25), with an α-terminal cholesterol group. Subsequent ring-opening of the pendant oxazolone group with various functional amines [i.e., 2-(2-aminoethyl)-1,3-di-Boc-guanidine (BG), 1-(3-aminopropyl)imidazole (IMID), N-Boc-ethylenediamine (BEDA), or N,N-dimethylethylenediamine (DMEN)] yielded an 11 functional cationic lipidated oligomer (CLOs) library, which comprised different cationic elements with the same terminal lipid cholesterol element. These CLOs exhibited greater activity against all tested fungal pathogens (Candida albicans, Cryptococcus neoformans, Candida tropicalis, Candida glabrata, Cryptococcus deuterogattii, and Candida auris), compared to the bacterial pathogens (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa or methicillin-resistant Staphylococcus aureus [MRSA]). Specifically, the DMEN and BEDA (after deprotection) series exhibited superior antifungal activities 4-16 times greater [determined by the minimum inhibitory concentration (MIC) in μg mL-1] than the clinically relevant antifungal fluconazole. Two 'hit' CLOs (Chol-DMEN-25 and Chol-BEDA-10) were identified, which inhibited both single sp. (C. albicans, C. tropicalis, C. neoformans, or C. gattii) and dual sp. (C. albicans and C. tropicalis) biofilm formation, and were able to attenuate mature biofilms, with a >50% mature biofilm biomass reduction at 128 μg mL-1. Co-delivery of fluconazole with two 'hit' CLOs demonstrated additive and synergistic effects on the aforementioned single-species and dual-species fungi biofilms, with a synergy score (SS) ranging from ∼3 to 15 and most synergistic area score (MSAS) ∼13-29 (by a Bliss independence model). The mechanistic studies (PI assay and nucleic acid release assay) revealed that these CLOs disrupted the integrity of fungal cell membranes. These results demonstrate that cholesterol terminated CLOs are potential antifungal candidates.

Shape-Shifting Mechanisms: Integrative Multi-Omics Insights Into Candida albicans Morphogenesis

The ability of Candida albicans to switch among yeast, hyphal, and pseudohyphal forms underlies its adaptability and pathogenicity. While cAMP-dependent signaling has long been considered central to hyphal growth, recent multi-omics studies show that cAMP-independent mechanisms also drive morphological changes. Basal PKA activity, cyclin-dependent kinases (e.g., Cdc28), and other regulators can promote shape-shifting even without classical cAMP pathways. In addition, N-acetylglucosamine (GlcNAc) acts as a potent signal that induces hyphal growth independently of its metabolic role, directly connecting environmental cues to morphological states. By integrating transcriptomic, proteomic, and phosphoproteomic data, this review exposes the intricate networks controlling C. albicans morphogenesis. A clearer understanding of these complex regulatory circuits lays the groundwork for future studies that employ advanced multi-omics analyses. Such approaches will help elucidate how these pathways converge, how they respond to changing environments, and how they might be harnessed or disrupted to influence fungal behavior.

Fungal infection monitoring on corneal epithelium ex vivo model and its collection over polyethersulfone membrane for detecting Candida albicans and Aspergillus fumigatus

In this paper we report a human ex vivo model of Aspergillus fumigatus and Candida albicans infection of the cornea. We demonstrate the ability to monitor fungal growth on the cornea through optical and immunofluorescence microscopy. Additionally, we establish a method for collection of fungal antigens in polyethersulfone (PES) membrane-based sample collectors from the surface of fungal inoculated corneas. Immunofluorescence microscopy was performed directly on both corneal tissue and PES membrane sample collectors. For the latter case, we devised an original ad-hoc method by attaching the membranes used for the collection on standard glass slides, which we call glass slide KIT. This enabled easy handling and improved efficiency for specifically recognizing the corresponding fungal infections by simple immunoassay protocols. As a result, we firstly observe the ability to monitor fungi in corneal tissue, and secondly demonstrate the adsorption of fungal antigens onto PES membranes. Thus, we report for the first time the specific detection of fungal corneal infections in easy to use PES membrane based glass slide KITs through simple immunofluorescence, as an alternative to microbiological culture.

Image-based quantification of Candida albicans filamentation and hyphal length using the open-source visual programming language JIPipe

The formation of hyphae is one of the most crucial virulence traits the human pathogenic fungus Candida albicans possesses. The assessment of hyphal length in response to various stimuli, such as exposure to human serum, provides valuable insights into the adaptation strategies of C. albicans to the host environment. Despite the increasing high-throughput capacity live-cell imaging and data generation, the accurate analysis of hyphal growth has remained a laborious, error-prone, and subjective manual process. We developed an analysis pipeline utilizing the open-source visual programming language Java Image Processing Pipeline (JIPipe) to overcome the limitations associated with manual analysis of hyphal growth. By comparing our automated approach with manual analysis, we refined the strategies to achieve accurate differentiation between yeast cells and hyphae. The automated method enables length measurements of individual hyphae, facilitating a time-efficient, high-throughput, and user-friendly analysis. By utilizing this JIPipe analysis approach, we obtained insights into the filamentation behavior of two C. albicans strains when exposed to human serum albumin (HSA), the most abundant protein in human serum. Our findings indicate that despite the known role of HSA in stimulating fungal growth, it reduces filamentous growth. The implementation of our automated JIPipe analysis approach for hyphal growth represents a long-awaited and time-efficient solution to meet the demand of high-throughput data generation. This tool can benefit different research areas investigating the virulence aspects of C. albicans.

Aloin remodels the cell wall of Candida albicans to reduce its hyphal virulence against oral candidiasis

Aloe vera (L.) Burm.f. is a traditional Chinese medicine known for treating various ailments, including fungal infections. Aloin is one of the major components from A. vera, but its antifungal mechanism and therapeutic potential against oral candidiasis are not clear. This study aimed to examine the mechanism of aloin against Candida albicans and its inhibitory activity against oral candidiasis. In this study, we for the first time found that aloin could induce the formation of abnormal hyphae with smaller hyphal diameters and fewer branching points in C. albicans including 11 clinical isolates without growth inhibition. The transcriptome and further cell wall contents analysis indicated that aloin remodeled the cell wall to increase the contents of β-1,3-glucan and furtherly showed an antagonistic effect with micafungin. Aloin also significantly inhibited the cell damage of oral epithelial cells and oral candidiasis in mice infected by C. albicans due to its inhibitory actions on the hyphal development and expressions of virulence factors, including candidalysin (coded by ECE1). Our results suggest that aloin is a promising antifungal agent for controlling candidiasis and targeting hyphal development and pathogenesis represents a practical strategy for developing new antifungal drugs. KEY POINTS: • Aloin remodels the C. albicans cell wall to form avirulent hyphae. • Aloin inhibits C. albicans infections in oral epithelial cells and mouse mucosa without toxicity. • Aloin is a promising antifungal agent with therapeutic potential against C. albicans infections.

A microbial natural product fractionation library screen with HRMS/MS dereplication identifies new lipopeptaibiotics against Candida auris

The rise of drug-resistant fungal pathogens, including Candida auris, highlights the urgent need for novel antifungal therapies. We developed a cost-effective platform combining microbial extract prefractionation with rapid MS/MS-bioinformatics-based dereplication to efficiently prioritize new antifungal scaffolds. Screening C. auris and C. albicans revealed novel lipopeptaibiotics, coniotins, from Coniochaeta hoffmannii WAC11161, which were undetectable in crude extracts. Coniotins exhibited potent activity against critical fungal pathogens on the WHO Fungal Priority Pathogens List, including C. albicans, C. neoformans, multidrug-resistant C. auris, and Aspergillus fumigatus, with high selectivity and low resistance potential. Coniotin A targets β-glucan, compromising fungal cell wall integrity, remodelling, and sensitizing C. auris to caspofungin. Identification of a PKS-NRPS biosynthetic gene cluster further enables the discovery of related clusters encoding potential novel lipopeptaibiotics. This study demonstrates the power of natural product prefractionation in uncovering bioactive scaffolds and introduces coniotins as promising candidates for combating multidrug-resistant fungal pathogens.

Efficacy of lipid nanoparticles-based vaccine to protect against vulvovaginal candidiasis (VVC): Implications for women's reproductive health

AIMS

Vulvovaginal candidiasis (VVC) is a common women's health issue, with rising antifungal resistance. This study was aimed to prepare and evaluate the efficacy of a lipid nanoparticle-based vaccine in a murine model of VVC.

MATERIALS AND METHODS

Dried and reconstituted vesicles containing C. albicans antigens (DRNPs-Ca-Ags) vaccine, formulated with phosphatidylcholine and cholesterol-based lipid nanoparticles via film hydration and freeze-drying. The safety evaluation of DRNPs-CaAgs was conducted by determining hepatic (AST, ALT) or renal (BUN, creatinine) biomarkers. Female mice were immunized with DRNPs-CaAgs or Alum-CaAgs, and immune responses were evaluated via antibody titers, IgG isotypes, and splenocyte proliferation. Protective efficacy of vaccine formulations was assessed through fungal burden, biofilm formation, cytokine levels, and histopathological analysis of vaginal tissues.

KEY FINDINGS

Mice vaccinated with DRNPs-CaAgs showed significantly enhanced immune responses, with higher antibody titers and IgG2a levels as compared to the Alum-CaAgs group. Vaginal fungal burden was dramatically reduced (665 ± 78 CFUs in DRNPs-CaAgs immunized group vs. 12,944 ± 3540 CFUs in Alum-CaAgs group, p < 0.01). Biofilm formation decreased by 45 % (p < 0.05), and inflammatory cytokines were significantly lowered. Histopathological analysis revealed minimal tissue damage in DRNPs-CaAgs vaccinated mice.

SIGNIFICANCE

The findings suggest DRNPs-CaAgs as a promising vaccine for VVC, eliciting strong immunity, reducing fungal load, and minimizing inflammation. While the reliance on a murine model is a limitation, future clinical trials are essential to evaluate its efficacy and safety in humans, offering a potential strategy to combat drug-resistant infections and improve women's reproductive health.

'Sneaky' uninflamed oesophageal candidiasis: morphological clues and comparison with candidiasis associated with inflammation

AIMS

Candida esophagitis is usually readily identified on routine H&E-stained sections as the infection typically presents with prominent acute inflammation as a clue to search for organisms. However, in some cases, inflammation is absent, and detection of organisms relies on the observation of zones exhibiting parakeratosis with a delicate 'flaky' appearance. Our study aimed to establish a correlation between the histomorphology of oesophageal candidiasis and an associated clinical profile.

METHODS

We reviewed 53 sequential biopsy specimens from patients with Candida esophagitis collected over 1 year. Biopsies were assessed for acute inflammation, intraepithelial lymphocytosis and lymphoid aggregates. Patients' medical records were reviewed for data on age, gender, race, immune status, smoking, corticosteroid use, HIV status and organ transplantation history. Correlations between these factors and histomorphological patterns were assessed using test.

RESULTS

Of the 53 biopsies, 20 lacked acute inflammation and 33 had it. 15 biopsies showed both acute and lymphoid inflammation and 5 showed lymphocytosis only. Among 16 smokers, 6 (37%) had acute inflammation and 10 (63%) had parakeratosis. In non-smokers, 24 (71%) had acute inflammation and 10 (29%) had parakeratosis. A significant correlation was found between smoking and absence of acute neutrophilic infiltration (p=0.025), but no other clinical factor was associated with inflammatory patterns.

CONCLUSIONS

Candida esophagitis can be uninflamed with 'flaky' parakeratosis or associated with acute inflammation or lymphocytosis with or without neutrophilic infiltration. Inflammation was often absent in smokers, suggesting synergistic local immunosuppressive effect is this overall immunosuppressed population.

Unconventional approaches for the induction of microbial natural products

Expansion of the microbial drug discovery pipeline has been impeded by a limited and skewed appreciation of the microbial world and its full chemical capabilities and by an inability to induce silent biosynthetic gene clusters (BGCs). Typically, these silent genes are not expressed under standard laboratory conditions, instead requiring particular interventions to activate them. Genetic, physical, and chemical strategies have been employed to trigger these BGCs, and some have resulted in the induction of novel secondary metabolites. This review encompasses a wide range of literature and emphasizes selected successful induction of microbial secondary metabolites examples through unconventional approaches such as quorum sensing, epigenetic modulation, and ribosome engineering. Whenever applicable, we will also discuss their mechanisms and optimizations to improve the microbial drug discovery process.

Clinical Characteristics and In Vivo Confocal Microscopic Study in Candida Keratitis

Purpose

To clarify the clinical and imaging characteristics of Candida keratitis using in vivo confocal microscopy (IVCM) for improved early diagnosis and management.

Methods

A retrospective study of 40 patients with Candida keratitis at Beijing Tongren Hospital from January 2015 to December 2023 was conducted. Data included demographics, risk factors, clinical assessments, lab tests, and IVCM images. Ex vivo confocal microscopy and methylene blue staining of Candida colonies were also analyzed to complement the findings.

Results

Key risk factors identified were topical steroid use, intraocular surgery history, and systemic diseases. Common clinical signs included multifocal infiltration, cream-colored infiltration, and blurred boundary lesions. IVCM on 37 eyes (92.5%) consistently showed round, highly reflective Candida spores, and short rod-shaped spores in some cases. Spores exhibited two patterns: caviar-like clusters (51.4%) and sand-like dispersion (89.2%). Multifocal infiltration was significantly associated with a greater prevalence of clustered spores (75.0% vs. 33.3%; P < 0.05). Candida pseudo-hyphae appeared as beaded (91.7%) or lotus root-shaped (41.7%), highly reflective structures. These IVCM findings closely matched colony ex vivo confocal microscopy and light microscopy observations. After treatment, 45% of patients required surgery owing to minimal improvement in best-corrected visual acuity. Poor outcomes were linked to cream-colored infiltration, blurred lesions boundaries, hypopyon, high inflammatory cell density, and deep Candida infiltration (P < 0.05). Clustered spores suggested better outcomes, but lacked statistical significance (P > 0.05).

Conclusions

IVCM effectively identifies characteristic spores and pseudo-hyphae in Candida keratitis, facilitating early detection and timely management, particularly in cases with multifocal infiltration and blurred boundary lesions.

Translational Relevance

IVCM works well for the early diagnosis of Candida keratitis, especially in cases of deep corneal stromal infiltration or corneal interface infection after corneal transplantation.

Long-chain 4-aminoquinolines inhibit filamentation and increase efficacy of nystatin against Candida albicans infections in vivo

In exploring a growing demand for innovative approaches to tackle emerging and life threatening fungal diseases, we identified long-chain 4-aminoquinoline (4-AQ) derivatives as a new class of anti-virulence agents. For the first time, we demonstrated that 4-AQs effectively prevent filamentation of Candida albicans, a key virulence trait, under multiple triggering conditions. Selected 4-AQ derivatives inhibited filament formation in a zebrafish model of disseminated candidiasis at 1.56 µM, with no toxicity up to 50 µM. Combining nystatin with 4-AQs resulted in a 100% survival rate of infected embryos and complete eradication of C. albicans, compared to 65-75% survival with nystatin alone. The most potent 4-AQ derivatives also showed significant activity against C. albicans biofilms, with derivative 11 suppressing mixed C. albicans-Pseudomonas aeruginosa biofilms. This dual capability highlights the potential of 4-AQs as novel anti-virulence agents to enhance conventional antifungal therapies, marking a significant advance in treating complex fungal infections.

Calcofluor White-Phosphatidylethanolamine Conjugate-Enhanced Ethosomal Delivery of Voriconazole for Targeting Candida albicans

Introduction

The increasing prevalence of systemic fungal infections, especially among immunocompromised individuals, highlights the need for advancements in targeted and effective antifungal treatments. This study presents a novel nanomaterial, CFW-phosphatidylethanolamine conjugate (CFW-PEc), designed to enhance the delivery and efficacy of antifungal agents by targeting fungal cell walls through specific chitin binding. Ethosomes, lipid-based nanocarriers known for their ability to improve drug delivery across skin and cell membranes, were utilized in this study.

Methods

The physicochemical characteristics of voriconazole-loaded CFW-PEc ethosomes (CFW-PEc-VRC-ethosomes) were examined, including particle size, zeta potential, and entrapment efficiency. Antifungal efficacy of CFW-PEc-VRC-ethosomes was evaluated, including antifungal activity in vitro, CFW-PEc-ethosomes cellular uptake, and models of animal infection and imaging analyses.

Results

In vitro experiments demonstrated a concentration-dependent inhibition of C. albicans growth by CFW-PEc, with cell inhibition rates reaching nearly 100% at 256 μM. In vivo investigations confirmed a 5-fold reduction in fungal burden in the liver and a 7.8-fold reduction in the kidney compared to the control group following treatment with CFW-PEc (0.1 μM)-VRC-ethosomes. Imaging analyses also confirmed the extended tissue retention of fluorescent dye-loaded CFW-PEc-ethosomes in mice, further underscoring their potential for clinical use.

Discussion

The targeted delivery of antifungal medications via ethosomes coated with CFW-PEc presents a promising strategy to improve antifungal effectiveness while reducing adverse effects, marking a significant advancement in fungal infection therapy.

Evaluating the Antifungal Potential of Cinnamaldehyde: A Study of its Efficacy against Candida Species

Candida species exist as commensals in nature, colonizing the mucous membranes, gastrointestinal tract, vagina as well as the skin and usually cause infections in immunocompromised patients. C. albicans are known to be the most prevalent Candida species associated with infections, while there has been a significant surge in the incidence of Non-Candida albicans Candida species (NCAC) recently. The recent occurrences of the antifungal resistance in Candida, especially in NCAC species are quite alarming which raises the need for a safe and efficient alternative antimycotic drug. This study analyses the efficacy of cinnamaldehyde against Candida species, which is known to cause the majority of the fungal infections in humans. Cinnamaldehyde is a natural antimicrobial compound derived from cinnamon and has demonstrated significant antimycotic properties. Antifungal susceptibility profiles of cinnamaldehyde against Candida species were studied by disc diffusion as well as by broth microdilution assays. The mean diameter of the inhibition zone (IZ) formed by direct contact and disc volatilization assays were 61.26 mM and 65.20 mM, respectively. Both the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) of cinnamaldehyde ranged from 16-256 mg/L with mean MIC of 60.61 mg/L and a mean MFC of 81.94 mg/L. Co-incubation of Candida cells with cinnamaldehyde resulted in the loss of viable cells within 4 hours of incubation. Cinnamaldehyde was found to exhibit both fungistatic and fungicidal properties, making it a potent natural alternative for conventional antifungal agents.

Ctr9 promotes virulence of Candida albicans by regulating methionine metabolism

Candida albicans, a part of normal flora, is an opportunistic fungal pathogen and causes severe health issues in immunocompromised patients. Its pathogenicity is intricately linked to the transcriptional regulation of its metabolic pathways. Paf1 complex (Paf1C) is a crucial transcriptional regulator that is highly conserved in eukaryotes. The objective of this study was to explore the role of Paf1C in the metabolic pathways and how it influences the pathogenicity of C. albicans. Paf1C knockout mutant strains of C. albicans (ctr9Δ/Δ, leo1Δ/Δ, and cdc73Δ/Δ) were generated using the CRISPR-Cas9 system. To investigate the effect of Paf1C on pathogenicity, macrophage interaction assays and mouse survival tests were conducted. The growth patterns of the Paf1C knockout mutants were analyzed through spotting assays and growth curve measurements. Transcriptome analysis was conducted under yeast conditions (30°C without serum) and hyphal conditions (37°C with 10% FBS), to further elucidate the role of Paf1C in the pathogenicity of C. albicans. CTR9 deletion resulted in the attenuation of C. albicans virulence, in macrophage and mouse models. Furthermore, we confirmed that the reduced virulence of the ctr9Δ/Δ mutant can be attributed to a decrease in C. albicans cell abundance. Moreover, transcriptome analysis revealed that metabolic processes required for cell proliferation are impaired in ctr9Δ/Δ mutant. Notably, CTR9 deletion led to the downregulation of methionine biosynthetic genes and the cAMP-PKA signaling pathway-related hypha essential genes, which are pivotal for virulence. Our results suggest that Ctr9-regulated methionine metabolism is a crucial factor for determining C. albicans pathogenicity.

The Effects of Carbonate on Candida albicans Filamentation, Biofilm Formation, and Antifungal Resistance

Candida albicans, a member of the normal microbial population of healthy humans, is an opportunistic pathogen that can cause serious disease in immunocompromised patients. An important virulence factor of C. albicans is the formation of biofilms. These organized communities of cells are efficient at attaching to host cells and implanted medical devices. Carbonate has been studied as an agricultural antifungal agent, and here we demonstrate that carbonate can affect filamentation, biofilm formation, and antifungal drug resistance in C. albicans.

Pathophysiological microenvironments in oral candidiasis

Oral candidiasis (OC), a prevalent opportunistic infection of the oral mucosa, presents a considerable health challenge, particularly in individuals with compromised immune responses, advanced age, and local predisposing conditions. A considerable part of the population carries Candida in the oral cavity, but only few develop OC. Therefore, the pathogenesis of OC may depend on factors other than the attributes of the fungus, such as host factors and other predisposing factors. Mucosal trauma and inflammation compromise epithelial integrity, fostering a conducive environment for fungal invasion. Molecular insights into the immunocompromised state reveal dysregulation in innate and adaptive immunity, creating a permissive environment for Candida proliferation. Detailed examination of Candida species (spp.) and their virulence factors uncovers a nuanced understanding beyond traditional C. albicans focus, which embrace diverse Candida spp. and their strategies, influencing adhesion, invasion, immune evasion, and biofilm formation. Understanding the pathophysiological microenvironments in OC is crucial for the development of targeted therapeutic interventions. This review aims to unravel the diverse pathophysiological microenvironments influencing OC development focusing on microbial, host, and predisposing factors, and considers Candida resistance to antifungal therapy. The comprehensive approach offers a refined perspective on OC, seeking briefly to identify potential therapeutic targets for future effective management.

Sodium lignosulfonate inhibits multiple virulent proteins of human fungal pathogen Candida albicans

Systemic mycoses, particularly those caused by Candida albicans, represent a serious global health concern due to rising multidrug resistance and limited treatment options. This study explores the antifungal potential of sodium lignosulfonate (LIG), a natural phenolic compound, as a multitarget therapeutic agent against various virulence proteins of C. albicans and other pathogenic Candida species. The objective of this study was to further evaluate its multiple-targeting/polypharmacological potential with plausible mode of action against C. albicans. At first, LIG was subjected to in-silico analysis to acquire preliminary knowledge about its multiple targeting potential. Subsequently, some biochemical analyses were performed to demonstrate its fungicidal activity. In-vitro analysis (plasma membrane permeation, ROS production, chitin depletion study) was performed to further validate its promising multiple-targeting/polypharmacological potential and revealed its mechanism of action. Homology modeling and docking studies revealed that LIG effectively binds to critical C. albicans proteins, including ERG1, ERG11, FKS1, CHS3, CLB2, and CEK1. The docking scores indicated strong interactions, supporting LIG's potential to inhibit multiple virulence factors With ROS production we could confirm the involvement of apoptosis. Time-kill assays confirmed the antifungal effect of LIG against C. albicans, C. glabrata, C. tropicalis, and C. parapsilosis. LIG demonstrated a > 3-log10 reduction in CFU/mL, and in combination with fluconazole, it showed synergistic activity, particularly reducing CFU in C. dubliniensis by 2.5-fold compared to fluconazole alone. The chitin depletion assay has reported a decrease in levels of chitin which indicates another aspect of LIG's mode of action. This study reveals LIG as a potent and persuasive natural antifungal agent that targets multiple proteins of Candida. This revelation might impact the direction of potent antifungal agent development by aiming multiple targets of fungal pathogens simultaneously.

Candida albicans cells exhibit media specific proteomic profiles during induction of filamentation

Candida albicans is an opportunist pathogen responsible for a broad spectrum of infections, from superficial mycosis to the systemic disease candidiasis. C. albicans has various morphological forms, including unicellular budding yeasts, filamentous pseudohyphae and true hyphae, and the ability to switch from yeast to hyphal forms is a key survival mechanism underlying the adaptation of the pathogen to the microenvironments encountered within the host. Filamentation is regulated by multiple signalling pathways and its induction in different growth media in vitro has often led to conflicting results. In this study, we performed quantitative proteomic analyses to compare the response of C. albicans yeast cells grown in YNB minimal medium to those of cells grown in four media widely used in the literature to induce the yeast-to-hyphae transition: YNB-Serum, YNB-N-acetylglucosamine (YNB-NAG), Lee medium and rich Spider medium. We show that each growth medium induces a unique pattern of response in C. albicans cells, and that some conditions trigger an original and specific adaptive metabolic response, showing significant differences in the intracellular content of the various filamentous forms. Moreover, this comparison of proteomic profiles indicates that the medium used can modify the thiol-dependent redox status of the cells, particularly in YNB-Serum and Lee medium and, to a lesser extent, in Spider medium, confirming the role of oxidative stress in the filamentation process. Overall, our data indicate that some of the media routinely used to induce hyphae cause significant changes in proteomic signature that should be taken account more carefully when exploring the hyphal transition in this pathogen.

Pullulan nanoparticles inhibit the pathogenicity of Candida albicans by regulating hypha-related gene expression

Candida albicans is a prevalent opportunistic pathogenic fungus that resides in the skin and gastrointestinal (GI) tract of humans. Under specific conditions, C. albicans cells transition from a commensal to a pathogenic state, leading to both superficial and invasive infections. Although systemic candidiasis poses a life-threatening risk, a limited number of antifungal drugs are employed for its treatment. Moreover, the emergence of resistant strains to antifungal agents underscores the pressing need for new treatment options. In this study, we propose the use of polysaccharide nanoparticles as a strategy for treating candidiasis. We synthesized phthalic pullulan nanoparticles (PPNPs) and examined their ability to inhibit the pathogenicity of C. albicans. We observed that PPNPs inhibit hyphal growth, adhesion to abiotic surfaces, and biofilm formation of C. albicans in a dose-dependent manner. This inhibitory effect is mediated by transcriptional modulation, particularly the downregulation of hypha-related genes and the upregulation of stress-responsive genes, involving the Ras/cAMP/PKA signaling pathway. Furthermore, we observed that PPNPs inhibit the adhesion of C. albicans to human epithelial cells without inducing toxicity in human cells. In addition, PPNPs inhibited the in vivo pathogenicity of C. albicans in Caenorhabditis elegans, suggesting an antagonistic effect on candidiasis. Our findings suggest that PPNPs exhibit inhibitory effects on C. albicans biofilm formation and in vivo pathogenicity, indicating their potential as a novel therapeutic agent for candidiasis.

IMPORTANCE

The pathogenic process of Candida albicans, the primary causative species of candidiasis, involves hyphal growth, biofilm formation, and secretion of virulence factors. Of these factors, the biofilm, created by the secretion of extracellular matrix from adherent cells, shields cells from external threats, enabling them to withstand high concentrations of antifungal agents. Therefore, suppressing biofilm formation is a crucial aspect of combating candidiasis. This study developed phthalic pullulan nanoparticles (PPNPs) as a novel material for inhibiting C. albicans' pathogenicity. PPNPs were internalized within Candida cells and reduced pathogenicity at the gene expression level, resulting in reduced in vitro biofilm formation, adhesion to human cells, and mortality of infected Caenorhabditis elegans. Moreover, PPNPs exhibited these effects without toxicity to human cells and host animals. These findings not only indicate that PPNPs can be employed to hinder in vitro biofilm formation but also suggest their potential as a novel treatment for candidiasis.

Reactive oxygen species sensitive nanomicelles promote the antifungal activity of ketoconazole against Candida albicans in vulvovaginal candidiasis

Excessive local accumulation of reactive oxygen species (ROS) in vulvovaginal candidiasis (VVC) leads to oxidative stress and aggravates inflammation. This study aimed to optimize and synthesize four ROS-sensitive polyethylene glycol (PEG)-boride polymers (PB, PCB, BPB, and BCPCB). A nanomicelle (BCPCB-K) was constructed using BCPCB-encapsulated ketoconazole (KTZ). Finally, the depolymerization principle and ROS-sensitive drug release of BCPCB-K as well as its anti-Candida albicans (CA) and therapeutic effects on mice with VVC were explored through in vitro and in vivo experiments. BCPCB-K exhibited low toxicity to mammalian cells in vitro and good biocompatibility in vivo. It also improved the dispersion and solubility of the hydrophobic drug KTZ. Furthermore, BCPCB-K simultaneously scavenged ROS and released the drug, thus facilitating the antifungal and VVC-treating effects of KTZ. Overall, the findings of this study broadened the application of ROS-sensitive materials in the drug-loading and antifungal fields and provided a strategy for VVC treatment.

Molecular characterization, carbohydrate metabolism and tolerance to abiotic stress of Eremothecium coryli endophytic isolates from fruits of Momordica indica

Yeasts are unicellular fungi that occur in a wide range of ecological niches, where they perform numerous functions. Furthermore, these microorganisms are used in industrial processes, food production, and bioremediation. Understanding the physiological and adaptive characteristics of yeasts is of great importance from ecological, biotechnological, and industrial perspectives. In this context, we evaluated the abilities to assimilate and ferment different carbon sources, to produce extracellular hydrolytic enzymes, and to tolerate salt stress, heavy metal stress, and UV-C radiation of two isolates of Eremothecium coryli, isolated from Momordica indica fruits. The two isolates were molecularly identified based on sequencing of the 18S-ITS1-5.8S-ITS2 region. Our isolates were able to assimilate nine carbon sources (dextrose, galactose, mannose, cellobiose, lactose, maltose, sucrose, melezitose, and pectin) and ferment three (glucose, maltose, and sucrose). The highest values of cellular dry weight were observed in the sugars maltose, sucrose, and melezitose. We observed the presence of hyphae and pseudohyphae in all assimilated carbon sources. The two isolates were also capable of producing amylase, catalase, pectinase, and proteases, with the highest values of enzymatic activity found in amylase. Furthermore, the two isolates were able to grow in media supplemented with copper, iron, manganese, nickel, and zinc and to tolerate saline stress in media supplemented with 5% NaCl. However, we observed a decrease in CFU at higher concentrations of these metals and NaCl. We also observed morphological changes in the presence of metals, which include changes in cell shape and cellular dimorphisms. The isolates were sensitive to UV-C radiation in the shortest exposure time (1 min). Our findings reinforce the importance of endophytic yeasts for biotechnological and industrial applications and also help to understand how these microorganisms respond to environmental variations caused by human activities.

A novel pH-responsive monomer inhibits Candida albicans via a dual antifungal mode of action

The scarcity of the antifungal drug arsenal highlights an urgent need to develop alternative treatments for candidiasis caused by Candida albicans (C. albicans). As pH is closely associated with C. albicans infection, it could be an essential target in a novel approach for designing antifungal therapy. In this study, a novel intelligent antifungal monomer, dodecylmethylaminoethyl methacrylate (DMAEM), with a pH-responsive tertiary amine group and a methacrylate-derived CC double bond group is developed. It is uncovered that the two functional groups of DMAEM contribute to a dual mode of action. Under acidic pH, the tertiary amine of DMAEM protonates into a cationic fungicide, sharing similar structural and functional characteristics with quaternary ammonium salts, which exerts fungicidal activity by targeting the CHK1 two-component system in C. albicans. At neutral pH, the methacrylate-derived CC double bond group contributes to anti-virulence activity by blocking hyphal formation. In addition, it is also identified that DMAEM suppresses filamentation by altering the extracellular vesicles of C. albicans. These findings support that the novel intelligent pH-responsive monomer could be a therapeutic candidate for treating candidiasis.

Host-microbe interaction paradigms in acute and recurrent vulvovaginal candidiasis

Candida spp. are members of the human mucosal microbiota that can cause opportunistic diseases ranging from superficial infections to life-threatening invasive candidiasis. In humans, the most common infection caused by Candida spp. is vulvovaginal candidiasis (VVC), which affects >70% of women at least once in their lifetime. Of those women, ∼5%-10% develop recurrent VVC (RVVC). In this review, we summarize our current understanding of the host and fungal factors that contribute to susceptibility to VVC and RVVC. We synthesize key findings that support the notion that disease symptoms are driven by neutrophil-associated dysfunction and immunopathology and describe how antifungal immune mechanisms in the vagina are distinct from other mucosal barrier sites. Finally, we highlight key, unanswered research areas within the field that can help us better understand the immunopathogenesis of this infection and facilitate the development of novel preventive, therapeutic, and/or vaccination strategies to combat these common, poorly understood diseases.

Conserved signaling modules regulate filamentous growth in fungi: a model for eukaryotic cell differentiation

Eukaryotic organisms are composed of different cell types with defined shapes and functions. Specific cell types are produced by the process of cell differentiation, which is regulated by signal transduction pathways. Signaling pathways regulate cell differentiation by sensing cues and controlling the expression of target genes whose products generate cell types with specific attributes. In studying how cells differentiate, fungi have proved valuable models because of their ease of genetic manipulation and striking cell morphologies. Many fungal species undergo filamentous growth-a specialized growth pattern where cells produce elongated tube-like projections. Filamentous growth promotes expansion into new environments, including invasion into plant and animal hosts by fungal pathogens. The same signaling pathways that regulate filamentous growth in fungi also control cell differentiation throughout eukaryotes and include highly conserved mitogen-activated protein kinase (MAPK) pathways, which is the focus of this review. In many fungal species, mucin-type sensors regulate MAPK pathways to control filamentous growth in response to diverse stimuli. Once activated, MAPK pathways reorganize cell polarity, induce changes in cell adhesion, and promote the secretion of degradative enzymes that mediate access to new environments. However, MAPK pathway regulation is complicated because related pathways can share components with each other yet induce unique responses (i.e. signal specificity). In addition, MAPK pathways function in highly integrated networks with other regulatory pathways (i.e. signal integration). Here, we discuss signal specificity and integration in several yeast models (mainly Saccharomyces cerevisiae and Candida albicans) by focusing on the filamentation MAPK pathway. Because of the strong evolutionary ties between species, a deeper understanding of the regulation of filamentous growth in established models and increasingly diverse fungal species can reveal fundamentally new mechanisms underlying eukaryotic cell differentiation.

Discovery of petroselinic acid with in vitro and in vivo antifungal activity by targeting fructose-1,6-bisphosphate aldolase

BACKGROUND

The incidence of invasive fungal diseases (IFDs), represented by Candida albicans infection, is increasing year by year. However, clinically available antifungal drugs are very limited and encounter challenges such as limited efficacy, drug resistance, high toxicity, and exorbitant cost. Therefore, there is an urgent need for new antifungal drugs.

PURPOSE

This study aims to find new antifungal compounds from plants, preferably those with good activity and low toxicity, and reveal their antifungal targets.

METHODS

In vitro antifungal activities of compounds were investigated using broth microdilution method, spot assay, hyphal growth assay and biofilm formation assay. Synergistic effects were assessed using broth microdilution checkerboard technique. In vivo antifungal activities were evaluated using Galleria mellonella and murine candidiasis models. Cytotoxicity of compounds was investigated using Cell Counting Kit-8 (CCK-8). Discovery and validation of antifungal targets of compounds were conducted by using monoallelic knockout library of C. albicans, haploinsufficiency profiling (HIP), thermal shift assay (TSA), enzyme inhibitory effect assay, molecular docking, and in vitro and in vivo antifungal studies.

RESULTS

814 plant products were screened, among which petroselinic acid (PeAc) was found as an antifungal molecule. As a rare fatty acid isolated from coriander (Coriandrum sativum), carrot (Daucus carota) and other plants of the Apiaceae family, PeAc had not previously been found to have antifungal effects. In this study, PeAc was revealed to inhibit the growth of various pathogenic fungi, exhibited synergistic effects with fluconazole (FLC), inhibited the formation of C. albicans hyphae and biofilms, and showed antifungal effects in vivo. PeAc was less toxic to mammalian cells. Fructose-1,6-bisphosphate aldolase (Fba1p) was identified as a target of PeAc by using HIP, TSA, enzyme inhibitory effect assay and molecular docking methods. PeAc exerted antifungal effects more effectively on fba1Δ/FBA1 than wild-type (WT) strain both in vitro and in vivo.

CONCLUSIONS

PeAc is an effective and low toxic antifungal compound. The target of PeAc is Fba1p. Fba1p is a promising target for antifungal drug development.

Clinical Features, Risk Factors, and Management of Candida Keratitis

BACKGROUND/AIMS

To determine the clinical features, predisposing factors, and management of infectious keratitis caused by Candida spp.

METHODS

Retrospective chart review.

RESULTS

The medical records of 52 patients (54 eyes) with Candida keratitis were available for statistical analysis. Thinning of the corneal stroma was identified in 34 eyes (63.0%), and corneal perforation occurred in 16 eyes (29.6%). Corneal thinning and perforation were more common in Candida albicans compared with non-albicans (P-val < .001, P = .09, respectively). The most common predisposing factors for Candida keratitis were topical steroid use (21 patients, 40.4%), previous corneal transplantation (17 patients, 32.7%), and preexisting ocular surface disease (15 patients, 28.8%). Fourteen eyes (25.9%) required cyanoacrylate glue application and 10 eyes (18.5%) underwent therapeutic penetrating keratoplasty (TPK).

CONCLUSION

Local immunosuppression and ocular surface disease play an important role in Candida keratitis. C. albicans appears to be more invasive compared with non-albicans spp.

Bioorthogonal labeling of chitin in pathogenic Candida species reveals biochemical mechanisms of hyphal growth and homeostasis

Pathogenic fungi rely on the cell wall component, chitin, for critical structural and immunological functions. Here a chitin labeling method to visualize the hyphal pathogenic response was developed. The data show that filamentous fungi, Candida albicans , transport N -acetylglucosamine (NAG) bio-orthogonal probes and incorporate them into the cell wall, indicating the probes utility for in vivo study of the morphological, pathogenic switch. As yeast reside in complex microenvironments, The data show that the opportunistic microbe C. albicans , has developed processes to utilize surrounding bacterial cell wall fragments to initiate the morphogenic switch. The probes are utilized for visualization of growth patterns of pathogenic fungi, providing insights into novel mechanisms for the development of antifungals. Remodeling chitin in fungi using NAG derivatives will advance yeast pathogenic studies.

Effects of Sucrose and Farnesol on Biofilm Formation by Streptococcus mutans and Candida albicans

Candida albicans (C. albicans) and Streptococcus mutans (S. mutans) are frequently detected in the plaque biofilms of children with early childhood caries. This study investigated the effects of sucrose and farnesol on biofilm formation by the oral pathogens S. mutans and C. albicans, including their synergistic interactions. Biofilm formation dynamics were monitored using the Cell Index (CI). The CI for S. mutans increased in the brain-heart infusion medium, peaking at 10 h; however, the addition of sucrose reduced the CI. For C. albicans yeast cells, the CI increased at sucrose concentrations > 0.5%, peaking at 2 h. Mixed cultures of S. mutans and C. albicans yeast cells showed significantly higher CI values in the presence of sucrose, suggesting a synergistic effect on biofilm formation. Farnesol consistently suppressed biofilm formation by C. albicans yeast cells, even in the presence of sucrose, and higher farnesol concentrations resulted in greater inhibition. Regarding C. albicans hyphal cells, sucrose did not enhance biofilm formation, whereas farnesol significantly reduced biofilm formation at all concentrations tested. These findings elucidate the complex roles of sucrose and farnesol in biofilm formation by S. mutans and C. albicans and emphasize the potential of farnesol as an effective oral biofilm inhibitor.

The spliceosome impacts morphogenesis in the human fungal pathogen Candida albicans

At human body temperature, the fungal pathogen Candida albicans can transition from yeast to filamentous morphologies in response to host-relevant cues. Additionally, elevated temperatures encountered during febrile episodes can independently induce C. albicans filamentation. However, the underlying genetic pathways governing this developmental transition in response to elevated temperatures remain largely unexplored. Here, we conducted a functional genomic screen to unravel the genetic mechanisms orchestrating C. albicans filamentation specifically in response to elevated temperature, implicating 45% of genes associated with the spliceosome or pre-mRNA splicing in this process. Employing RNA-Seq to elucidate the relationship between mRNA splicing and filamentation, we identified greater levels of intron retention in filaments compared to yeast, which correlated with reduced expression of the affected genes. Intriguingly, homozygous deletion of a gene encoding a spliceosome component important for filamentation (PRP19) caused even greater levels of intron retention compared with wild type and displayed globally dysregulated gene expression. This suggests that intron retention is a mechanism for fine-tuning gene expression during filamentation, with perturbations of the spliceosome exacerbating this process and blocking filamentation. Overall, this study unveils a novel biological process governing C. albicans filamentation, providing new insights into the complex regulation of this key virulence trait.IMPORTANCEFungal pathogens such as Candida albicans can cause serious infections with high mortality rates in immunocompromised individuals. When C. albicans is grown at temperatures encountered during human febrile episodes, yeast cells undergo a transition to filamentous cells, and this process is key to its virulence. Here, we expanded our understanding of how C. albicans undergoes filamentation in response to elevated temperature and identified many genes involved in mRNA splicing that positively regulate filamentation. Through transcriptome analyses, we found that intron retention is a mechanism for fine-tuning gene expression in filaments, and perturbation of the spliceosome exacerbates intron retention and alters gene expression substantially, causing a block in filamentation. This work adds to the growing body of knowledge on the role of introns in fungi and provides new insights into the cellular processes that regulate a key virulence trait in C. albicans.

Variations in candidalysin amino acid sequence influence toxicity and host responses

Candida albicans causes millions of mucosal infections in humans annually. Hyphal overgrowth on mucosal surfaces is frequently associated with tissue damage caused by candidalysin, a secreted peptide toxin that destabilizes the plasma membrane of host cells thereby promoting disease and immunopathology. Candidalysin was first identified in C. albicans strain SC5314, but recent investigations have revealed candidalysin "variants" of differing amino acid sequence in isolates of C. albicans, and the related species C. dubliniensis, and C tropicalis, suggesting that sequence variation among candidalysins may be widespread in natural populations of these Candida species. Here, we analyzed ECE1 gene sequences from 182 C. albicans isolates, 10 C. dubliniensis isolates, and 78 C. tropicalis isolates and identified 10, 3, and 2 candidalysin variants in these species, respectively. Application of candidalysin variants to epithelial cells revealed differences in the ability to cause cellular damage, changes in metabolic activity, calcium influx, MAPK signalling, and cytokine secretion, while biophysical analyses indicated that variants exhibited differences in their ability to interact with and permeabilize a membrane. This study identifies candidalysin variants with differences in biological activity that are present in medically relevant Candida species.

IMPORTANCE

Fungal infections are a significant burden to health. Candidalysin is a toxin produced by Candida albicans that damages host tissues, facilitating infection. Previously, we demonstrated that candidalysins exist in the related species C. dubliniensis and C. tropicalis, thereby identifying these molecules as a toxin family. Recent genomic analyses have highlighted the presence of a small number of candidalysin "variant" toxins, which have different amino acid sequences to those originally identified. Here, we screened genome sequences of isolates of C. albicans, C. dubliniensis, and C. tropicalis and identified candidalysin variants in all three species. When applied to epithelial cells, candidalysin variants differed in their ability to cause damage, activate intracellular signaling pathways, and induce innate immune responses, while biophysical analysis revealed differences in the ability of candidalysin variants to interact with lipid bilayers. These findings suggest that intraspecies variation in candidalysin amino acid sequence may influence fungal pathogenicity.

Synergic Effect of the Antimicrobial Peptide ToAP2 and Fluconazole on Candida albicans Biofilms

Candida albicans is one of the agents of invasive candidiasis, a life-threatening disease strongly associated with hospitalization, particularly among patients in intensive care units with central venous catheters. This study aimed to evaluate the synergistic activity of the antifungal peptide ToAP2 combined with fluconazole against C. albicans biofilms grown on various materials. We tested combinations of different concentrations of the peptide ToAP2 with fluconazole on C. albicans biofilms. These biofilms were generated on 96-well plates, intravenous catheters, and infusion tubes in RPMI medium at two maturation stages. Scanning electron microscopy and atomic force microscopy were employed to assess the biofilm structure. We also evaluated the expression of genes previously proven to be involved in C. albicans biofilm formation in planktonic and biofilm cells after treatment with the peptide ToAP2 using qPCR. ToAP2 demonstrated a synergistic effect with fluconazole at concentrations up to 25 µM during both the early and mature stages of biofilm formation in 96-well plates and on medical devices. Combinations of 50, 25, and 12.5 µM of ToAP2 with 52 µM of fluconazole significantly reduced the biofilm viability compared to individual treatments and untreated controls. These results were supported by substantial structural changes in the biofilms observed through both scanning and atomic force microscopy. The gene expression analysis of C. albicans cells treated with 25 µM of ToAP2 revealed a decrease in the expression of genes associated with membrane synthesis, along with an increase in the expression of genes involved in efflux pumps, adhesins, and filamentation. Our results highlight the efficacy of the combined ToAP2 and fluconazole treatment against C. albicans biofilms. This combination not only shows therapeutic potential but also suggests its utility in developing preventive biofilm tools for intravenous catheters.

Exploring the role of candidalysin in the pathogenicity of Candida albicans by gene set enrichment analysis and evolutionary dynamics

AIMS

To explore the pathogenic mechanisms of Candida albicans (C. albicans), focusing on its impact on human health, particularly through invasive infections in the gastrointestinal and respiratory tracts.

METHODS

In this study, we evaluated the demographic and clinical profiles of 7 pneumonia patients. Meanwhile, we used Gene Set Enrichment Analysis (GSEA) and Evolutionary Dynamics method to analyze the role of candidalysin in C. albicans pathogenicity.

RESULTS

By analyzing genomic data and conducting biomedical text mining, we identified novel mutation sites in the candidalysin coding gene ECE1-III, shedding light into the genetic diversity within C. albicans strains and their potential implications for antifungal resistance. Our results revealed significant associations between C. albicans and respiratory as well as gastrointestinal diseases, emphasizing the fungus's role in the pathogenesis of these diseases. Additionally, we identified a new mutation site in the C. albicans strain YF2-5, isolated from patients with pneumonia. This mutation may be associated with its heightened pathogenicity.

CONCLUSION

Our research advances the understanding of C. albicans pathogenicity and opens new avenues for developing targeted antifungal therapies. By focusing on the molecular basis of fungal virulence, we aim to contribute to the development of more effective treatment strategies, addressing the challenge of multidrug resistance in invasive fungal infections.

The Vps21 signalling pathway regulates white-opaque switching and mating in Candida albicans

Candida albicans is able to switch between two epigenetic cell types, namely white and opaque. Multiple conserved signalling pathways control the switch between white and opaque cell types in response to environmental changes. Here, we report the regulatory roles of the endosomal Rab family GTPase Vps21 and associated key components of the Vps21 signalling pathway in white-opaque switching and mating in C. albicans. Deletion of VPS21 promoted a switch from the white to the opaque phenotype in the presence of N-acetyl-glucosamine (GlcNAc). Consistently, inactivation of the guanine nucleotide exchange factor of Vps21 (Vps9) and downstream components in the Vps21 pathway (Vps3, Vac1, and Pep12) had similar promoting effects on phenotypic switching. The mating efficiency of opaque cells is much higher than that of white cells under standard laboratory culture conditions. However, compared to the wildtype strain, the vps21/vps21, vps9/vps9, vps3/vps3, vac1/vac1, and pep12/pep12 mutant strains exhibited dramatically reduced mating efficiencies. Quantitative RT-PCR assays demonstrated that inactivation of the Vps21 signalling pathway led to downregulation of pheromone expression and mating response pathway associated genes. Taken together, our findings indicate that the conserved Vps21 signalling pathway plays critical roles in the regulation of cell-type switching and mating in C. albicans.

Molecular Determinants Involved in Candida albicans Biofilm Formation and Regulation

Candida albicans is known for its pathogenicity, although it lives within the human body as a commensal member. The commensal nature of C. albicans is well controlled and regulated by the host's immune system as they live in the harmonized microenvironment. However, the development of certain unusual microhabitat conditions (change in pH, co-inhabiting microorganisms' population ratio, debilitated host-immune system) pokes this commensal fungus to transform into a pathogen in such a way that it starts to propagate very rapidly and tries to breach the epithelial barrier to enter the host's systemic circulations. In addition, Candida is infamous as a major nosocomial (hospital-acquired infection) agent because it enters the human body through venous catheters or medical prostheses. The hysterical mode of C. albicans growth builds its microcolony or biofilm, which is pathogenic for the host. Biofilms propose additional resistance mechanisms from host immunity or extracellular chemicals to aid their survival. Differential gene expressions and regulations within the biofilms cause altered morphology and metabolism. The genes associated with adhesiveness, hyphal/pseudo-hyphal growth, persister cell transformation, and biofilm formation by C. albicans are controlled by myriads of cell-signaling regulators. These genes' transcription is controlled by different molecular determinants like transcription factors and regulators. Therefore, this review has focused discussion on host-immune-sensing molecular determinants of Candida during biofilm formation, regulatory descriptors (secondary messengers, regulatory RNAs, transcription factors) of Candida involved in biofilm formation that could enable small-molecule drug discovery against these molecular determinants, and lead to disrupt the well-structured Candida biofilms effectively.

Candida albicans and Candida glabrata: global priority pathogens

SUMMARYA significant increase in the incidence of Candida-mediated infections has been observed in the last decade, mainly due to rising numbers of susceptible individuals. Recently, the World Health Organization published its first fungal pathogen priority list, with Candida species listed in medium, high, and critical priority categories. This review is a synthesis of information and recent advances in our understanding of two of these species-Candida albicans and Candida glabrata. Of these, C. albicans is the most common cause of candidemia around the world and is categorized as a critical priority pathogen. C. glabrata is considered a high-priority pathogen and has become an increasingly important cause of candidemia in recent years. It is now the second most common causative agent of candidemia in many geographical regions. Despite their differences and phylogenetic divergence, they are successful as pathogens and commensals of humans. Both species can cause a broad variety of infections, ranging from superficial to potentially lethal systemic infections. While they share similarities in certain infection strategies, including tissue adhesion and invasion, they differ significantly in key aspects of their biology, interaction with immune cells, host damage strategies, and metabolic adaptations. Here we provide insights on key aspects of their biology, epidemiology, commensal and pathogenic lifestyles, interactions with the immune system, and antifungal resistance.

Structure and interactions of prion-like domains in transcription factor Efg1 phase separation

Candida albicans, a prominent member of the human microbiome, can make an opportunistic switch from commensal coexistence to pathogenicity accompanied by an epigenetic shift between the white and opaque cell states. This transcriptional switch is under precise regulation by a set of transcription factors (TFs), with Enhanced Filamentous Growth Protein 1 (Efg1) playing a central role. Previous research has emphasized the importance of Efg1's prion-like domain (PrLD) and the protein's ability to undergo phase separation for the white-to-opaque transition of C. albicans. However, the underlying molecular mechanisms of Efg1 phase separation have remained underexplored. In this study, we delved into the biophysical basis of Efg1 phase separation, revealing the significant contribution of both N-terminal (N) and C-terminal (C) PrLDs. Through NMR structural analysis, we found that Efg1 N-PrLD and C-PrLD are mostly disordered but have prominent partial α-helical secondary structures in both domains. NMR titration experiments suggest that the partially helical structures in N-PrLD act as hubs for self-interaction as well as Efg1 interaction with RNA. Using condensed-phase NMR spectroscopy, we uncovered diverse amino acid interactions underlying Efg1 phase separation. Particularly, we highlight the indispensable role of tyrosine residues within the transient α-helical structures of PrLDs particularly in the N-PrLD compared to the C-PrLD in stabilizing phase separation. Our study provides evidence that the transient α-helical structure is present in the phase-separated state and highlights the particular importance of aromatic residues within these structures for phase separation. Together, these results enhance the understanding of C. albicans transcription factor interactions that lead to virulence and provide a crucial foundation for potential antifungal therapies targeting the transcriptional switch.

Optimisation of garlic mustard oil macerate with respect to its antifungal activity against Candida albicans MTCC 183 and in-silico molecular docking of the volatile compounds with N-myristoyltransferase

Candida albicans infections are widespread in people and cause cutaneous and systemic infections. Optimisation of garlic mustard oil macerate (GMM) based on antifungal activity against C. albicans was done using agar diffusion method. Upon vapour diffusion assay, the volatile organic compounds of both GMM and MO were found to eradicate C. albicans. During agar diffusion, MO did not inhibit fungal growth, while undiluted GMM oil demonstrated a 26.33 ± 0.33 mm zone of inhibition. The minimum inhibitory concentration and minimum fungicidal concentration against C. albicans were 12.5%, v/v of GMM oil and 25%, v/v of GMM oil, respectively. Scanning electron microscopy analysis showed cell membrane disintegration of fungal cells by 50%, v/v of GMM oil, and MO caused no cell wall damage. In-silico analysis revealed strong binding affinity of sinigrin, ajoene, dithiin with N-myristoyltransferase. In conclusion, the optimised GMM preparation can be a potential antifungal agent against tropical C. albicans infections.