Polyunsaturated fatty acids cause apoptosis in C. albicans and C. dubliniensis biofilms

Studies on the Inhibition Mechanism of Linalyl Alcohol against the Spoilage Microorganism Brochothrix thermosphacta

The aim of this study was to investigate the bacterial inhibitory ability and mechanism of action of linalyl alcohol against B. thermosphacta. Linalyl alcohol causes the leakage of intracellular material by disrupting the cell wall and exposing the hydrophobic phospholipid bilayer, which binds to bacterial membrane proteins and alters their structure. In addition, linalyl alcohol causes cell membrane damage by affecting fatty acids and proteins in the cell membrane. By inhibiting the synthesis of macromolecular proteins, the normal physiological functions of the bacteria are altered. Linalyl alcohol binds to DNA in both grooved and embedded modes, affecting the normal functioning of B. thermosphacta, as demonstrated through a DNA interaction analysis.

Identification of bioactive compounds of Bacillus velezensis HNA3 that contribute to its dual effects as plant growth promoter and biocontrol against post-harvested fungi

IMPORTANCE

The current study is an extension to our previous work on the plant growth-promoting rhizobacteria (PGPR) Bacillus velezensis HNA3 strain, which comes to confirm and reveals the huge stock of active secondary metabolites produced by HNA3. HNA3-emitted volatile organic compounds (VOCs) have demonstrated the capacity to impede the growth of phytopathogens affecting some fruits and vegetables, even in the absence of direct contact. Additionally, these volatiles enhanced soybean seed germination by breaking seed dormancy and inducing root system development. Furthermore, they promoted seedling growth, giving it prominence in soybean cultivation. The relevance of active volatiles derives from the fact that they can be developed as natural-safe biocontrol agents and plant promoters. This research validates the remarkable bioactivities exhibited by the Bacillus velezensis HNA3 and their potential applications in agriculture as an inoculant, encompassing biocontrol, plant growth promotion, and seed germination activities, thereby offering a safer alternative to hazardous chemicals.

Activity of propolis from Mexico on the proliferation and virulence factors of Candida albicans

BACKGROUND

This research evaluated the anti-Candida albicans effect of Mexican propolis from Chihuahua. Chemical composition of the ethanolic extract of propolis was determined by GC-MS, HPLC-DAD, and HPLC-MS. The presence of anthraquinone, aromatic acid, fatty acids, flavonoids, and carbohydrates was revealed.

RESULTS

The anti-Candida activity of propolis was determined. The inhibitions halos were between 10.0 to 11.8 mm; 25% minimum inhibitory concentration (0.5 mg/ml) was fungistatic, and 50% minimum inhibitory concentration (1.0 mg/ml) was fungicidal. The effect of propolis on the capability of C. albicans to change its morphology was evaluated. 25% minimum inhibitory concentration inhibited to 50% of germ tube formation. Staining with calcofluor-white and propidium iodide was performed, showing that the propolis affected the integrity of the cell membrane. INT1 gene expression was evaluated by qRT-PCR. Propolis significantly inhibited the expression of the INT1 gene encodes an adhesin (Int1p). Chihuahua propolis extract inhibited the proliferation of Candida albicans, the development of the germ tube, and the synthesis of adhesin INT1.

CONCLUSIONS

Given the properties demonstrated for Chihuahua propolis, we propose that it is a candidate to be considered as an ideal antifungal agent to help treat this infection since it would not have the toxic effects of conventional antifungals.

Eicosapentaenoic acid influences the pathogenesis of Candida albicans in Caenorhabditis elegans via inhibition of hyphal formation and stimulation of the host immune response

The intake of omega-3 polyunsaturated fatty acids, including eicosapentaenoic acid (EPA), is associated with health benefits due to its anti-inflammatory properties. This fatty acid also exhibits antifungal properties in vitro. In order to determine if this antifungal property is valid in vivo, we examined how EPA affects Candida albicans pathogenesis in the Caenorhabditis elegans infection model, an alternative to mammalian host models. The nematodes were supplemented with EPA prior to infection, and the influence of EPA on C. elegans lipid metabolism, survival and immune response was studied. In addition, the influence of EPA on hyphal formation in C. albicans was investigated. It was discovered that EPA supplementation changed the lipid composition, but not the unsaturation index of C. elegans by regulating genes involved in fatty acid and eicosanoid production. EPA supplementation also delayed killing of C. elegans by C. albicans due to the inhibition of hyphal formation in vivo, via the action of the eicosanoid metabolite of EPA, 17,18-epoxyeicosatetraenoic acid. Moreover, EPA supplementation also caused differential expression of biofilm-related gene expression in C. albicans and stimulated the immune response of C. elegans. This provides a link between EPA and host susceptibility to microbial infection in this model.

A Re-Purposing Strategy: Sub-Lethal Concentrations of an Eicosanoid Derived from the Omega-3-Polyunsaturated Fatty Acid Resolvin D1 Affect Dual Species Biofilms

The fungal species Candida parapsilosis and the bacterial species Staphylococcus aureus may be responsible for hospital-acquired infections in patients undergoing invasive medical interventions or surgical procedures and often coinfect critically ill patients in complicating polymicrobial biofilms. The efficacy of the re-purposing therapy has recently been reported as an alternative to be used. PUFAs (polyunsaturated fatty acids) may be used alone or in combination with currently available traditional antimicrobials to prevent and manage various infections overcoming antimicrobial resistance. The objectives of the study were to evaluate the effects of Resolvin D1 (RvD1) as an antimicrobial on S. aureus and C. parapsilosis, as well as the activity against the mixed biofilm of the same two species. Microdilution assays and time-kill growth curves revealed bacterial and fungal inhibition at minimum concentration values between 5 and 10 μg mL-1. In single-species structures, an inhibition of 55% and 42% was reported for S. aureus and C. parapsilosis, respectively. Moreover, RvD1 demonstrated an eradication capacity of 60% and 80% for single- and mixed-species biofilms, respectively. In association with the inhibition activity, a downregulation of genes involved in biofilm formation as well as ROS accumulation was observed. Eradication capability was confirmed also on mature mixed biofilm grown on silicone platelets as shown by scanning electron microscopy (SEM). In conclusion, RvD1 was efficient against mono and polymicrobial biofilms in vitro, being a promising alternative for the treatment of mixed bacterial/fungal infections.

High-throughput assay for effect screening of amphotericin B and bioactive components on filamentous Candida albicans

AIMS

The aim of this study was to develop a high-throughput robotic microtiter plate-based screening assay for Candida albicans, optimizing growth conditions to replicate the filamentous biofilm growth found in vivo, and subsequently, to demonstrate the assay by evaluating the effect of nutritional drinks alone and in combination with the antifungal amphotericin B (AmB).

METHODS AND RESULTS

Candida albicans cultured in a defined growth medium showed filamentous growth in microcolonies, mimicking the morphology of oral mucosal disease (oral candidiasis). Addition of nutrient drinks containing fruit juices, fish oil and whey protein to the medium resulted in changed morphology and promoted growth as free yeast cells and with weak biofilm structures. Minimum inhibitory concentration of AmB on the biofilms was 0.25 μg ml^-1 , and this was eightfold reduced (0.0038 μg ml^-1 ) in the presence of the nutritional drinks.

CONCLUSIONS

The established assay demonstrated applicability for screening of antifungal and anti-biofilm effects of bioactive substances on C. albicans biofilm with clinically relevant morphology.

SIGNIFICANCE AND IMPACT OF THE STUDY

Candida albicans is the causative agent of the majority of fungal infections globally. The filamentous morphology of C. albicans and the ability to form biofilm are traits known to increase virulence and resistance towards antifungals. This study describes the development of a plate-based in vitro screening method mimicking the filamentous morphology of C. albicans found in vivo. The assay established can thus facilitate efficient antifungal drug discovery and development.

Access to Anti-Biofilm Compounds from Endolichenic Fungi Using a Bioguided Networking Screening

Endolichenic microorganisms represent a new source of bioactive natural compounds. Lichens, resulting from a symbiotic association between algae or cyanobacteria and fungi, constitute an original ecological niche for these microorganisms. Endolichenic fungi inhabiting inside the lichen thallus have been isolated and characterized. By cultivation on three different culture media, endolichenic fungi gave rise to a wide diversity of bioactive metabolites. A total of 38 extracts were screened for their anti-maturation effect on Candida albicans biofilms. The 10 most active ones, inducing at least 50% inhibition, were tested against 24 h preformed biofilms of C. albicans, using a reference strain and clinical isolates. The global molecular network was associated to bioactivity data in order to identify and priorize active natural product families. The MS-targeted isolation led to the identification of new oxygenated fatty acid in Preussia persica endowed with an interesting anti-biofilm activity against C. albicans yeasts.

Antibiofilm Activity of Essential Fatty Acids Against Candida albicans from Vulvovaginal Candidiasis and Bloodstream Infections

Purpose

Methods

Results

Conclusion

The Potential of Fatty Acids and Their Derivatives as Antifungal Agents: A Review

Fungal contamination presents several problems: in humans, health issues arise from infections with opportunistic filamentous fungi and yeast, while in food, fungi cause spoilage and, in particular, in the case of mycotoxigenic fungi, can cause serious health issues. Several types of fatty acids and their derivatives, oxylipins, have been found to have inhibitory effect towards fungal growth and the production of mycotoxins. The use of fatty acids as antifungals could fulfil consumer’s requests of more natural and environmentally friendly compounds, while being less likely to promote fungal resistance. In addition, due to their nature, fatty acids are easily used as food additives. In this work, we review the most relevant and recent studies on the antifungal ability of fatty acids. We focused on saturated fatty acids, unsaturated fatty acids, and oxylipins, their different impact on fungal inhibition, their proposed modes of action, and their ability to impair mycotoxin production. Applications of fatty acids as antifungals and their limitations are also addressed.

UPLC-ESI-MS/MS profiling of the underground parts of common Iris species in relation to their anti-virulence activities against Staphylococcusaureus

ETHNOPHARMACOLOGICAL RELEVANCE

The use of plant extracts and their phytochemicals as candidates for targeting the microbial resistance inhibition is increasingly focused in last decades. In Mongolian traditional medicine, Irises were long used for the treatment of bacterial infections. Irises have been used since the Ancient Egyptians.

AIM OF THE STUDY

Chemical composition and virulence inhibition potential of both polar (PF) and non-polar fractions (NPF) of three common Iris species (I. confusa, I. pseudacorus and I. germanica) were explored.

MATERIAL AND METHODS

Secondary metabolites profiling was characterized by the UPLC-HRMS/MS technique. Multi-variate data analysis was performed using Metaboanalyst 3.0. Anti-virulence inhibitory activity was evaluated via anti-haemolytic assay and Quantitative biofilm inhibition assay.

RESULTS

I. pseudacorus PF exhibited the most potent effect against S. aureus haemolytic activity. All the tested fractions from all species, except I. pseudacorus NPF, have no significant inhibition on the biofilm formation of methicillin resistant and sensitive (MRSA and MSSA) S. aureus. I. pseudacorus NPF showed potent biofilm inhibitory potential of 71.4 and 85.8% against biofilm formation of MRSA and MSSA, respectively. Metabolite profiling of the investigated species revealed ninety and forty-five metabolites detected in the PFs and NPFs, respectively. Nigricin-type, tectorigenin-type isoflavonids and xanthones allowed the discrimination of I. pseudacorus PF from the other species, highlighting the importance of those metabolites in exerting its promising activity. On the other hand, triterpene acids, iridals, triacylglycerols and ceramides represented the metabolites detected in highest abundance in I. pseudacorus NPF.

CONCLUSIONS

This is the sole map represents the secondary metabolites profiling of the PFs and NPFs of common Iris species correlating them with the potent explored Staphylococcus aureus anti-virulence activity.

Long-chain unsaturated fatty acids are involved in the viability and itraconazole susceptibility of Aspergillus fumigatus

The prevalence of invasive aspergillosis with azole resistance is increasing, but the mechanisms underlying the development of resistance and treatment strategies are still limited. The present work is focused on finding a relationship between long-chain unsaturated fatty acids (LCUFAs), Aspergillus fumigatus development, and antifungal resistance. The effects of LCUFAs on antifungal agents in vitro were determined, and the stearic acid desaturase gene (sdeA) of A. fumigatus was characterized. In in vitro antifungal tests, LCUFAs antagonized the antifungal activity of itraconazole by extracting it from media, thereby preventing it from entering cells. The OA auxotrophic phenotype caused by an sdeA deletion confirmed that SdeA was required for OA biosynthesis in A. fumigatus. Furthermore, several low-level sdeA-overexpressing mutants with impaired vegetative growth phenotypes were successfully constructed. Additionally, an sdeA-overexpressing mutant, OEsdeA-5, showed lowered sensitivity levels to itraconazole. Moreover, RNA sequencing of OEsdeA-5 revealed that the altered gene-expression pattern. Through targeted metabolomics, decreased palmitic acid and stearic acid contents, accompanied by higher palmitoleic acid, margaroleic acid, and OA production levels, were found in OEsdeA-5. This study provides a novel insight of understanding of azole resistance and a potential target for drug development.

Fatty Acids and Oxylipins as Antifungal and Anti-Mycotoxin Agents in Food: A Review

Fungal contamination of food, especially by mycotoxigenic fungi, not only reduces the quality of the food, but can also cause serious diseases, thus posing a major food safety challenge to humans. Apart from sound food control systems, there is also a continual need to explore antifungal agents that can inhibit fungal growth and mycotoxin production in food. Many types of fatty acids (FAs) and their oxidized derivatives, oxylipins, have been found to exhibit such effects. In this review, we provide an update on the most recent literature on the occurrence and formation of FAs and oxylipins in food, their effects on fungal growth and mycotoxin synthesis, as well as the genetic and molecular mechanisms of actions. Research gaps in the field and needs for further studies in order to realizing the potential of FAs and oxylipins as natural antifungal preservatives in food are also discussed.

Inhibitory effect of polyunsaturated fatty acids alone or in combination with fluconazole on Candida krusei biofilms in vitro and in Caenorhabditis elegans

The incidence of infections by non-albicans Candida species, including Candida krusei, is increasing. Candida krusei exhibits intrinsic resistance to fluconazole and rapidly develops acquired resistance to other antifungals. Moreover, this yeast can form biofilm with increased resistance. Hence, there is a need to develop novel therapeutic strategies to combat infections caused by this pathogen. One such approach is through combination therapy with natural compounds, such as polyunsaturated fatty acids (PUFAs). This study aims to investigate the effect of PUFAs on fluconazole susceptibility of C. krusei biofilms, as well as the conserved nature of these effects in the Caenorhabditis elegans infection model. C. krusei biofilms were exposed to various fatty acids as well as combinations of fluconazole and linoleic acid (LA) or gamma-linolenic acid (GLA). The effect of these treatments on biofilm formation, cell ultrastructure, membrane integrity, oxidative stress and efflux pump activity was evaluated. In addition, the ability of the PUFAs to prolong survival and reduce the fungal burden of infected C. elegans, in the absence and presence of fluconazole, was assessed. Two P|UFAs, LA and GLA had he displayed significant inhibition of C. krusei biofilms and both of them increased the susceptibility of C. krusei biofilm to fluconazole in vitro via induction of oxidative stress, cell membrane damage, and disruption of efflux pump activity. These PUFAs also extended the lifespan of infected nematodes and displayed a potentiating effect with fluconazole in this model. This may pave the way for future studies into novel antifungal drug targets and treatment options.

LAY ABSTRACT

The pathogenic yeast, Candida krusei, is naturally resistant to the antifungal drug, fluconazole. This study finds that polyunsaturated fatty acids, linoleic and gamma-linolenic acid, can inhibit C. krusei and overcome this resistance of in vitro biofilms, as well as in a nematode infection model.

Inhibition of polymicrobial biofilm formation by saw palmetto oil, lauric acid and myristic acid

Biofilms are communities of bacteria, fungi or yeasts that form on diverse biotic or abiotic surfaces, and play important roles in pathogenesis and drug resistance. A generic saw palmetto oil inhibited biofilm formation by Staphylococcus aureus, Escherichia coli O157:H7 and fungal Candida albicans without affecting their planktonic cell growth. Two main components of the oil, lauric acid and myristic acid, are responsible for this antibiofilm activity. Their antibiofilm activities were observed in dual-species biofilms as well as three-species biofilms of S. aureus, E. coli O157:H7 and C. albicans. Transcriptomic analysis showed that lauric acid and myristic acid repressed the expressions of haemolysin genes (hla and hld) in S. aureus, several biofilm-related genes (csgAB, fimH and flhD) in E. coli and hypha cell wall gene HWP1 in C. albicans, which supported biofilm inhibition. Also, saw palmetto oil, lauric acid and myristic acid reduced virulence of three microbes in a nematode infection model and exhibited minimal cytotoxicity. Furthermore, combinatorial treatment of fatty acids and antibiotics showed synergistic antibacterial efficacy against S. aureus and E. coli O157:H7. These results demonstrate that saw palmetto oil and its main fatty acids might be useful for controlling bacterial infections as well as multispecies biofilms.

Plasma Membrane MCC/Eisosome Domains Promote Stress Resistance in Fungi

There is growing appreciation that the plasma membrane orchestrates a diverse array of functions by segregating different activities into specialized domains that vary in size, stability, and composition. Studies with the budding yeast Saccharomyces cerevisiae have identified a novel type of plasma membrane domain known as the MCC (membrane compartment of Can1)/eisosomes that correspond to stable furrows in the plasma membrane. MCC/eisosomes maintain proteins at the cell surface, such as nutrient transporters like the Can1 arginine symporter, by protecting them from endocytosis and degradation. Recent studies from several fungal species are now revealing new functional roles for MCC/eisosomes that enable cells to respond to a wide range of stressors, including changes in membrane tension, nutrition, cell wall integrity, oxidation, and copper toxicity. The different MCC/eisosome functions are often intertwined through the roles of these domains in lipid homeostasis, which is important for proper plasma membrane architecture and cell signaling. Therefore, this review will emphasize the emerging models that explain how MCC/eisosomes act as hubs to coordinate cellular responses to stress. The importance of MCC/eisosomes is underscored by their roles in virulence for fungal pathogens of plants, animals, and humans, which also highlights the potential of these domains to act as novel therapeutic targets.

Transcriptome Analyses of Candida albicans Biofilms, Exposed to Arachidonic Acid and Fluconazole, Indicates Potential Drug Targets

Candida albicans is an opportunistic yeast pathogen within the human microbiota with significant medical importance because of its pathogenic potential. The yeast produces highly resistant biofilms, which are crucial for maintaining infections. Though antifungals are available, their effectiveness is dwindling due to resistance. Alternate options that comprise the combination of existing azoles and polyunsaturated fatty acids, such as arachidonic acid (AA), have been shown to increase azoles susceptibility of C. albicans biofilms; however, the mechanisms are still unknown. Therefore, transcriptome analysis was conducted on biofilms exposed to sub-inhibitory concentrations of AA alone, fluconazole alone, and AA combined with fluconazole to understand the possible mechanism involved with the phenomenon. Protein ANalysis THrough Evolutionary Relationships (PANTHER) analysis from the differentially expressed genes revealed that the combination of AA and fluconazole influences biological processes associated with essential processes including methionine synthesis and those involved in ATP generation, such as AMP biosynthesis, fumarate metabolism and fatty acid oxidation. These observations suggests that the interference of AA with these processes may be a possible mechanisms to induce increased antifungal susceptibility.

Inhibition of Candida albicans and Staphylococcus aureus biofilms by centipede oil and linoleic acid

Microbial biofilms are associated with persistent infections because of their high tolerance to antimicrobial agents and host defenses. The effects of centipede oil from Scolopendra subspinipes mutilans and its main components were investigated to identify non-toxic biofilm inhibitors. Centipede oil and linoleic acid at 20 µg ml^-1 markedly inhibited biofilm formation by two fluconazole-resistant Candida albicans strains and three Staphylococcus aureus strains without affecting their planktonic cell growth. Also, both centipede oil and linoleic acid inhibited hyphal growth and cell aggregation by C. albicans. In addition, centipede oil and linoleic acid showed anti-biofilm activities against mixed C. albicans and S. aureus biofilms. Transcriptomic analysis showed that centipede oil and linoleic acid downregulated the expressions of several hypha/biofilm-related genes in C. albicans and α-hemolysin in S. aureus. Furthermore, both compounds effectively reduced C. albicans virulence in a nematode infection model with minimal toxicity.

Physiological and Transcriptional Responses of Candida parapsilosis to Exogenous Tyrosol

Tyrosol plays a key role in fungal morphogenesis and biofilm development. Also, it has a remarkable antifungal effect at supraphysiological concentrations. However, the background of the antifungal effect remains unknown, especially in the case of non-albicans Candida species such as Candida parapsilosis We examined the effect of tyrosol on growth, adhesion, redox homeostasis, virulence, as well as fluconazole susceptibility. To gain further insights into the physiological consequences of tyrosol treatment, we also determined genome-wide gene expression changes using transcriptome sequencing (RNA-Seq). A concentration of 15 mM tyrosol caused significant growth inhibition within 2 h of the addition of tyrosol, while the adhesion of yeast cells was not affected. Tyrosol increased the production of reactive oxygen species remarkably, as revealed by a dichlorofluorescein test, and it was associated with elevated superoxide dismutase, glutathione peroxidase, and catalase activities. The interaction between fluconazole and tyrosol was antagonistic. Tyrosol exposure resulted in 261 and 181 differentially expressed genes with at least a 1.5-fold increase or decrease in expression, respectively, which were selected for further study. Genes involved in ribosome biogenesis showed downregulation, while genes related to the oxidative stress response and ethanol fermentation were upregulated. In addition, tyrosol treatment upregulated the expression of efflux pump genes, including MDR1 and CDR1, and downregulated the expression of the FAD2 and FAD3 virulence genes involved in desaturated fatty acid formation. Our data demonstrate that exogenous tyrosol significantly affects the physiology and gene expression of C. parapsilosis, which could contribute to the development of treatments targeting quorum sensing in the future.IMPORTANCE Candida-secreted quorum-sensing molecules (i.e., farnesol and tyrosol) are key regulators in fungal physiology, which induce phenotypic adaptations, including morphological changes, altered biofilm formation, and synchronized expression of virulence factors. Moreover, they have a remarkable antifungal activity at supraphysiological concentrations. Limited data are available concerning the tyrosol-induced molecular and physiological effects on non-albicans Candida species such as C. parapsilosis In addition, the background of the previously observed antifungal effect caused by tyrosol remains unknown. This study reveals that tyrosol exposure enhanced the oxidative stress response and the expression of efflux pump genes, while it inhibited growth and ribosome biogenesis as well as several virulence-related genes. Metabolism was changed toward glycolysis and ethanol fermentation. Furthermore, the initial adherence was not influenced significantly in the presence of tyrosol. Our results provide several potential explanations for the previously observed antifungal effect.

Hexane extract from Spondias tuberosa (Anacardiaceae) leaves has antioxidant activity and is an anti-Candida agent by causing mitochondrial and lysosomal damages

Background

Spondias tuberosa is a plant that produces a fruit crop with high economic relevance at Brazilian Caatinga. Its roots and leaves are used in folk medicine.

Methods

Chemical composition of a hexane extract from S. tuberosa leaves was evaluated by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) and ¹H nuclear magnetic resonance (NMR). Antioxidant potential was investigated by DPPH and ABTS assays. Antifungal action on Candida species was evaluated determining the minimal inhibitory concentration (MIC₅₀) and putative mechanisms were determined by flow cytometry analysis. In addition, hemolytic activity on human erythrocytes was assessed and the concentration required to promote 50% hemolysis (EC₅₀) was determined.

Results

Phytochemical analysis by TLC showed the presence of flavonoids, hydrolysable tannins, saponins and terpenes. The HPLC profile of the extract suggested the presence of gallic acid (0.28 ± 0.01 g%) and hyperoside (1.27 ± 0.01 g%). The representative ¹H NMR spectrum showed saturated and unsaturated fatty acids among the main components. The extract showed weak and moderate antioxidant activity in DPPH (IC₅₀: 234.00 μg/mL) and ABTS (IC₅₀: 123.33 μg/mL) assays, respectively. It was able to inhibit the growth of C. albicans and C. glabrata with MIC₅₀ of 2.0 and 0.078 mg/mL, respectively. The treatment of C. glabrata cells with the extract increased levels of mitochondrial superoxide anion, caused hyperpolarization of mitochondrial membrane, and compromised the lysosomal membrane. Weak hemolytic activity (EC₅₀: 740.8 μg/mL) was detected.

Conclusion

The results demonstrate the pharmacological potential of the extract as antioxidant and antifungal agent, aggregating biotechnological value to this plant and stimulating its conservation.

Fungicidal PMMA-Undecylenic Acid Composites

Undecylenic acid (UA), known as antifungal agent, still cannot be used to efficiently modify commercial dental materials in such a way that this affects Candida. Actually, issues with Candida infections and fungal resistance compromise the use of Poly(methyl-methacrylate) (PMMA) as dental material. The challenge remains to turn PMMA into an antifugal material, which can ideally affect both sessile (attached) and planktonic (free-floating) Candida cells. We aimed to tackle this challenge by designing PMMA-UA composites with different UA concentrations (3-12%). We studied their physico-chemical properties, the antifungal effect on Candida and the cytotoxicity toward human cells. We found that UA changes the PMMA surface into a more hydrophilic one. Mainly, as-preparation composites with ≥6% UA reduced sessile Candida for >90%. After six days, the composites were still efficiently reducing the sessile Candida cells (for ~70% for composites with ≥6% UA). Similar results were recorded for planktonic Candida. Moreover, the inhibition zone increased along with the UA concentration. The antifungal effect of UA was also examined at the surface of an UA-loaded agar and the minimal inhibitory concentration (MIC90) was below the lowest-studied 0.0125% UA. Furthermore, the embedded filamentation test after 24 h and 48 h showed complete inhibition of the Candida growth at 0.4% UA.

Guidelines and recommendations on yeast cell death nomenclature

Elucidating the biology of yeast in its full complexity has major implications for science, medicine and industry. One of the most critical processes determining yeast life and physiology is cel-lular demise. However, the investigation of yeast cell death is a relatively young field, and a widely accepted set of concepts and terms is still missing. Here, we propose unified criteria for the defi-nition of accidental, regulated, and programmed forms of cell death in yeast based on a series of morphological and biochemical criteria. Specifically, we provide consensus guidelines on the differ-ential definition of terms including apoptosis, regulated necrosis, and autophagic cell death, as we refer to additional cell death rou-tines that are relevant for the biology of (at least some species of) yeast. As this area of investigation advances rapidly, changes and extensions to this set of recommendations will be implemented in the years to come. Nonetheless, we strongly encourage the au-thors, reviewers and editors of scientific articles to adopt these collective standards in order to establish an accurate framework for yeast cell death research and, ultimately, to accelerate the pro-gress of this vibrant field of research.

Lipoxygenase Activity Accelerates Programmed Spore Germination in Aspergillus fumigatus

The opportunistic human pathogen Aspergillus fumigatus initiates invasive growth through a programmed germination process that progresses from dormant spore to swollen spore (SS) to germling (GL) and ultimately invasive hyphal growth. We find a lipoxygenase with considerable homology to human Alox5 and Alox15, LoxB, that impacts the transitions of programmed spore germination. Overexpression of loxB (OE::loxB) increases germination with rapid advance to the GL stage. However, deletion of loxB (ΔloxB) or its signal peptide only delays progression to the SS stage in the presence of arachidonic acid (AA); no delay is observed in minimal media. This delay is remediated by the addition of the oxygenated AA oxylipin 5-hydroxyeicosatetraenoic acid (5-HETE) that is a product of human Alox5. We propose that A. fumigatus acquisition of LoxB (found in few fungi) enhances germination rates in polyunsaturated fatty acid-rich environments.

Providing lipid-based nutrient supplement during pregnancy does not reduce the risk of maternal P falciparum parasitaemia and reproductive tract infections: a randomised controlled trial

BACKGROUND

Maternal infections are associated with maternal and foetal adverse outcomes. Nutrient supplementation during pregnancy may reduce the occurrence of infections by improving maternal immunity. We aimed to investigate the impact of small-quantity lipid-based nutrient supplement (SQ-LNS) on the occurrence of Plasmodium falciparum parasitaemia during pregnancy and trichomoniasis, vaginal candidiasis and urinary tract infection (UTI) after delivery.

METHODS

Pregnant Malawian women enrolled in the iLiNS-DYAD trial receiving daily supplementation with SQ-LNS, multiple micronutrients (MMN) or iron & folic acid (IFA) from <20 gestation weeks (gw) were assessed for P. falciparum parasitaemia at 32 gw using rapid diagnostic testing (RDT), at 36 gw using polymerase chain reaction (PCR) and at delivery using both RDT and PCR; and at one week after delivery for trichomoniasis and vaginal candidiasis using wet mount microscopy and for UTI using urine dipstick analysis. The prevalence of each infection by intervention group was estimated at the prescribed time points and the global null hypothesis was tested using logistic regression. Adjusted analyses were performed using preselected covariates.

RESULTS

The prevalence of P. falciparum parasitaemia was 10.7% at 32 gw, 9% at 36 gw, and 8.3% by RDT and 20.2% by PCR at delivery. After delivery the prevalence of trichomoniasis was 10.5%, vaginal candidiasis was 0.5%, and UTI was 3.1%. There were no differences between intervention groups in the prevalence of any of the infections.

CONCLUSION

In this population, SQ-LNS did not influence the occurrence of maternal P. falciparum parasitaemia, trichomoniasis, vaginal candidiasis or UTI.

TRIAL REGISTRATION

Identifier: NCT01239693 (10 November 2010).

Protective effects of seabuckthorn pulp and seed oils against radiation-induced acute intestinal injury

Radiation-induced gastrointestinal syndrome, including nausea, diarrhea and dehydration, contributes to morbidity and mortality after medical or industrial radiation exposure. No safe and effective radiation countermeasure has been approved for clinical therapy. In this study, we aimed to investigate the potential protective effects of seabuckthorn pulp and seed oils against radiation-induced acute intestinal injury. C57/BL6 mice were orally administered seabuckthorn pulp oil, seed oil and control olive oil once per day for 7 days before exposure to total-body X-ray irradiation of 7.5 Gy. Terminal deoxynucleotidyl transferase dUTP nick end labeling, quantitative real-time polymerase chain reaction and western blotting were used for the measurement of apoptotic cells and proteins, inflammation factors and mitogen-activated protein (MAP) kinases. Seabuckthorn oil pretreatment increased the post-radiation survival rate and reduced the damage area of the small intestine villi. Both the pulp and seed oil treatment significantly decreased the apoptotic cell numbers and cleaved caspase 3 expression. Seabuckthorn oil downregulated the mRNA level of inflammatory factors, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-8. Both the pulp and seed oils elevated the level of phosphorylated extracellular-signal-regulated kinase and reduced the levels of phosphorylated c-Jun N-terminal kinase and p38. Palmitoleic acid (PLA) and alpha linolenic acid (ALA) are the predominant components of pulp oil and seed oil, respectively. Pretreatment with PLA and ALA increased the post-radiation survival time. In conclusion, seabuckthorn pulp and seed oils protect against mouse intestinal injury from high-dose radiation by reducing cell apoptosis and inflammation. ALA and PLA are promising natural radiation countermeasure candidates.

Repurposing of Aspirin and Ibuprofen as Candidate Anti-Cryptococcus Drugs

The usage of fluconazole and amphotericin B in clinical settings is often limited by, among other things, drug resistance development and undesired side effects. Thus, there is a constant need to find new drugs to better manage fungal infections. Toward this end, the study described in this paper considered the repurposing of aspirin (acetylsalicylic acid) and ibuprofen as alternative drugs to control the growth of cryptococcal cells. In vitro susceptibility tests, including a checkerboard assay, were performed to assess the response of Cryptococcus neoformans and Cryptococcus gattii to the above-mentioned anti-inflammatory drugs. Next, the capacity of these two drugs to induce stress as well as their mode of action in the killing of cryptococcal cells was determined. The studied fungal strains revealed a response to both aspirin and ibuprofen that was dose dependent, with ibuprofen exerting greater antimicrobial action. More importantly, the MICs of these drugs did not negatively (i) affect growth or (ii) impair the functioning of macrophages; rather, they enhanced the ability of these immune cells to phagocytose cryptococcal cells. Ibuprofen was also shown to act in synergy with fluconazole and amphotericin B. The treatment of cryptococcal cells with aspirin or ibuprofen led to stress induction via activation of the high-osmolarity glycerol (HOG) pathway, and cell death was eventually achieved through reactive oxygen species (ROS)-mediated membrane damage. The presented data highlight the potential clinical application of aspirin and ibuprofen as candidate anti-Cryptococcus drugs.

Flavodoxin-Like Proteins Protect Candida albicans from Oxidative Stress and Promote Virulence

The fungal pathogen Candida albicans causes lethal systemic infections in humans. To better define how pathogens resist oxidative attack by the immune system, we examined a family of four Flavodoxin-Like Proteins (FLPs) in C. albicans. In agreement with previous studies showing that FLPs in bacteria and plants act as NAD(P)H quinone oxidoreductases, a C. albicans quadruple mutant lacking all four FLPs (pst1Δ, pst2Δ, pst3Δ, ycp4Δ) was more sensitive to benzoquinone. Interestingly, the quadruple mutant was also more sensitive to a variety of oxidants. Quinone reductase activity confers important antioxidant effects because resistance to oxidation was restored in the quadruple mutant by expressing either Escherichia coli wrbA or mammalian NQO1, two distinct types of quinone reductases. FLPs were detected at the plasma membrane in C. albicans, and the quadruple mutant was more sensitive to linolenic acid, a polyunsaturated fatty acid that can auto-oxidize and promote lipid peroxidation. These observations suggested that FLPs reduce ubiquinone (coenzyme Q), enabling it to serve as an antioxidant in the membrane. In support of this, a C. albicans coq3Δ mutant that fails to synthesize ubiquinone was also highly sensitive to oxidative stress. FLPs are critical for survival in the host, as the quadruple mutant was avirulent in a mouse model of systemic candidiasis under conditions where infection with wild type C. albicans was lethal. The quadruple mutant cells initially grew well in kidneys, the major site of C. albicans growth in mice, but then declined after the influx of neutrophils and by day 4 post-infection 33% of the mice cleared the infection. Thus, FLPs and ubiquinone are important new antioxidant mechanisms that are critical for fungal virulence. The potential of FLPs as novel targets for antifungal therapy is further underscored by their absence in mammalian cells.

Reactive oxygen species-inducing antifungal agents and their activity against fungal biofilms

Invasive fungal infections are associated with very high mortality rates ranging from 20–90% for opportunistic fungal pathogens such as Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. Fungal resistance to antimycotic treatment can be genotypic (due to resistant strains) as well as phenotypic (due to more resistant fungal lifestyles, such as biofilms). With regard to the latter, biofilms are considered to be critical in the development of invasive fungal infections. However, there are only very few antimycotics, such as miconazole (azoles), echinocandins and liposomal formulations of amphotericin B (polyenes), which are also effective against fungal biofilms. Interestingly, these antimycotics all induce reactive oxygen species (ROS) in fungal (biofilm) cells. This review provides an overview of the different classes of antimycotics and novel antifungal compounds that induce ROS in fungal planktonic and biofilm cells. Moreover, different strategies to further enhance the antibiofilm activity of such ROS-inducing antimycotics will be discussed.

Aging and cell death in the other yeasts, Schizosaccharomyces pombe and Candida albicans

How do cells age and die? For the past 20 years, the budding yeast, Saccharomyces cerevisiae, has been used as a model organism to uncover the genes that regulate lifespan and cell death. More recently, investigators have begun to interrogate the other yeasts, the fission yeast, Schizosaccharomyces pombe, and the human fungal pathogen, Candida albicans, to determine if similar longevity and cell death pathways exist in these organisms. After summarizing the longevity and cell death phenotypes in S. cerevisiae, this mini-review surveys the progress made in the study of both aging and programed cell death (PCD) in the yeast models, with a focus on the biology of S. pombe and C. albicans. Particular emphasis is placed on the similarities and differences between the two types of aging, replicative aging, and chronological aging, and between the three types of cell death, intrinsic apoptosis, autophagic cell death, and regulated necrosis, found in these yeasts. The development of the additional microbial models for aging and PCD in the other yeasts may help further elucidate the mechanisms of longevity and cell death regulation in eukaryotes.