Candida Biofilms: An Update on Developmental Mechanisms and Therapeutic Challenges

Exploring the antifungal, antibiofilm and antienzymatic potential of Rottlerin in an in vitro and in vivo approach

Candida species have been responsible for a high number of invasive infections worldwide. In this sense, Rottlerin has demonstrated a wide range of pharmacological activities. Therefore, this study aimed to evaluate the antifungal, antibiofilm and antivirulence activity of Rottlerin in vitro against Candida spp. and its toxicity and antifungal activity in vivo. Rottlerin showed antifungal activity against all yeasts evaluated, presenting Minimum Inhibitory and Fungicidal Concentration (MIC and MFC) values of 7.81 to > 1000 µg/mL. Futhermore, it was able to significantly inhibit biofilm production, presenting Biofilm Inhibitory Concentration (MICB50) values that ranged from 15.62 to 250 µg/mL and inhibition of the cell viability of the biofilm by 50% (IC50) from 2.24 to 12.76 µg/mL. There was a considerable reduction in all hydrolytic enzymes evaluated, with emphasis on hemolysin where Rottlerin showed a reduction of up to 20%. In the scanning electron microscopy (SEM) analysis, Rottlerin was able to completely inhibit filamentation by C. albicans. Regarding in vivo tests, Rottlerin did not demonstrate toxicity at the therapeutic concentrations demonstrated here and was able to increase the survival of C. elegans larvae infected. The results herein presented are innovative and pioneering in terms of Rottlerin's multipotentiality against these fungal infections.

Marine Ascomycetes Extract Antifungal Susceptibility against Candida spp. Isolates from Oral Candidiasis HIV/AIDS Patient: An In Vitro Study

OBJECTIVE

 The etiology of oral candidiasis (OC) was Candida albicans, C. krusei, C. dubliniensis, C. tropicalis that are frequently found in human immunodeficiency virus/ acquired immunodeficiency syndrome (HIV/AIDS) patients. Marine ascomycetes (MA) have been widely reported as an important producer of various antibiotic compounds. However, there is limited study of antifungal compounds from MA against Candida species. The aim of this study was to investigate the antifungal susceptibility of MA against Candida spp. isolates from OC HIV/AIDS patient.

MATERIALS AND METHODS

 Trichoderma sp. is a sponge-associated fungus collected from Karimunjawa National Park, Central Java, Indonesia. The validation of C. albicans, C. krusei, C. dubliniensis, C. tropicalis. was done by ChromAgar. This study was true experimental with post-test only control group design; the sample was four replications for each group. Nystatin administration (K +), the golden standard antifungal drug, was used. The minimum fungicidal concentration (MFC), minimum inhibitory concentration (MIC), and diffusion zone methods were done. Analysis of variance difference test, and post-hoc Tukey's honest significant different were done to analyze the significant different between groups (p ≤ 0.05).

RESULTS

 The MFC and MIC of MA against C. albicans, C. krusei, C. dubliniensis, and C. tropicalis were found at 12.5%. In addition, the greatest diffusion zone of MA against C. albicans, C. krusei, C. dubliniensis, and C. tropicalis was found at 12.5%. There is no appreciable difference in antifungal activity between K + and 12.5% of MA extract (p ≥ 0.05).

CONCLUSION

 Concentration of 12.5% MA extract has antifungal susceptibility against Candida spp. isolates from OC HIV/AIDS patient.

Antifungal drug resistance in Candida: a special emphasis on amphotericin B

Invasive fungal infections in humans caused by several Candida species, increased considerably in immunocompromised or critically ill patients, resulting in substantial morbidity and mortality. Candida albicans is the most prevalent species, although the frequency of these organisms varies greatly according to geographic region. Infections with C. albicans and non-albicans Candida species have become more common, especially in the past 20 years, as a result of aging, immunosuppressive medication use, endocrine disorders, malnourishment, extended use of medical equipment, and an increase in immunogenic diseases. Despite C. albicans being the species most frequently associated with human infections, C. glabrata, C. parapsilosis, C. tropicalis, and C. krusei also have been identified. Several antifungal drugs with different modes of action are approved for use in clinical settings to treat fungal infections. However, due to the common eukaryotic structure of humans and fungi, only a limited number of antifungal drugs are available for therapeutic use. Furthermore, drug resistance in Candida species has emerged as a result of the growing use of currently available antifungal drugs against fungal infections. Amphotericin B (AmB), a polyene class of antifungal drugs, is mainly used for the treatment of serious systemic fungal infections. AmB interacts with fungal plasma membrane ergosterol, triggering cellular ion leakage via pore formation, or extracting the ergosterol from the plasma membrane inducing cellular death. AmB resistance is primarily caused by changes in the content or structure of ergosterol. This review summarizes the antifungal drug resistance exhibited by Candida species, with a special focus on AmB.

Epidemiology, clinical characteristics, outcome and biofilm forming properties in candidaemia: A single-centre retrospective 4-year analysis from Hungary

BACKGROUND

Candidaemia is a life-threatening disease that is associated with high mortality, especially in intensive care units (ICUs). The number of comprehensive studies dealing with the epidemiologic characteristics of biofilm-related properties is limited.

OBJECTIVE

This study evaluated the clinical characteristics of candidaemia, to assess the biofilm-forming properties of isolates, and to identify the risk factors of mortality.

PATIENTS AND METHODS

A total of 149 candidaemia episodes from the University of Debrecen, Clinical Centre, between January 2020 and December 2023 were investigated retrospectively. The susceptibility of Candida isolates to fluconazole, amphotericin B, anidulafungin, caspofungin, and micafungin was evaluated and compared to the susceptibility of 1-day-old biofilms. Multivariate logistic regression analysis was applied to identify the independent predictors of 30-day mortality rate.

RESULTS

The most common Candida species was Candida albicans (41%), followed by C. parapsilosis (20%), C. glabrata (14%), C. tropicalis (13%), rare Candida species (7%), and C. krusei (5%). Sixty-six percent of Candida isolates were biofilm formers and 44% had high metabolic activity. The 30-day mortality rate was 52%, which was higher in ICUs (65%). The logistic regression analysis revealed several factors significantly influencing mortality including ICU admission (odds ratio [OR] 2.99, 95% confidence interval [CI] 1.17-8.04, p = 0.025), fluconazole treatment (OR 4.12, 95% CI 1.62-11.42, p = .004), and pneumonia (OR 0.261, 95% CI 0.1-0.67, p = .006).

CONCLUSIONS

This comprehensive analysis supports the better characterisation of candidaemia in healthcare settings, which ultimately may reduce mortality among patients.

Gallic acid triphenylphosphonium derivatives TPP+-C10 and TPP+-C12 inhibit mitochondrial function in Candida albicans exerting antifungal and antibiofilm effects

AIMS

To evaluate the antifungal and antibiofilm activity of gallic acid derivatives TPP+-C10 and TPP+-C12 and their effects on mitochondrial function on two Candida albicans reference strains (ATCC 90029 and ATCC 10231).

METHODS AND RESULTS

First, we determined minimal inhibitory concentration (MIC) using a microdilution assay. Both compounds exerted antifungal effects, and their MICs ranged from 3.9 to 13 µM, with no statistically significant differences between them (P > 0.05, t-test). These concentrations served as references for following assays. Subsequently, we measured oxygen consumption with a Clark electrode. Our observations revealed that both drugs inhibited oxygen consumption in both strains with TPP+-C12 exerting a more pronounced inhibitory effect. We then employed flow cytometry with TMRE as a probe to assess mitochondrial membrane potential. For each strain assayed, the compounds induced a decay in transmembrane potential by 75%-90% compared to the control condition (P < 0.05, ANOVA). Then, we measured ATP levels using a commercial kit. TPP+-C12 showed a 50% decrease of ATP content (P < 0.05 ANOVA), while TPP+-C10 exhibited a less pronounced effect. Finally, we assessed the antibiofilm effect using the MTT reduction assay. Both compounds were effective, but TPP+-C12 displayed a greater potency, requiring a lower concentration to inhibit 50% of biofilms viability (P < 0.05, t-test).

CONCLUSIONS

Derivatives of gallic acid linked to a TPP+ group exert antifungal and antibiofilm activity through impairment of mitochondrial function in C. albicans.

Anti-Biofilm Activity of Cocultimycin A against Candida albicans

Candida albicans (C. albicans), the most common fungal pathogen, has the ability to form a biofilm, leading to enhanced virulence and antibiotic resistance. Cocultimycin A, a novel antifungal antibiotic isolated from the co-culture of two marine fungi, exhibited a potent inhibitory effect on planktonic C. albicans cells. This study aimed to evaluate the anti-biofilm activity of cocultimycin A against C. albicans and explore its underlying mechanism. Crystal violet staining showed that cocultimycin A remarkably inhibited biofilm formation in a dose-dependent manner and disrupted mature biofilms at higher concentrations. However, the metabolic activity of mature biofilms treated with lower concentrations of cocultimycin A significantly decreased when using the XTT reduction method. Cocultimycin A could inhibit yeast-to-hypha transition and mycelium formation of C. albicans colonies, which was observed through the use of a light microscope. Scanning electron microscopy revealed that biofilms treated with cocultimycin A were disrupted, yeast cells increased, and hypha cells decreased and significantly shortened. The adhesive ability of C. albicans cells treated with cocultimycin A to the medium and HOEC cells significantly decreased. Through the use of a qRT-PCR assay, the expression of multiple genes related to adhesion, hyphal formation and cell membrane changes in relation to biofilm cells treated with cocultimycin A. All these results suggested that cocultimycin A may be considered a potential novel molecule for treating and preventing biofilm-related C. albicans infections.

The inhibitory effect of photodynamic therapy on dual-species biofilms of Candida albicans and Candida krusei can be determined by Candida albicans/Candida krusei ratio

Candida krusei and Candida albicans present the ability to form communities of microorganisms called biofilms. Biofilms can be composed of a single species or more and are an important virulence factor. The inhibition of C. albicans and C. krusei as well as of their dual-species biofilms by antimicrobial Photodynamic Therapy (aPDT) has been demonstrated. This study aimed to investigate the effect of aPDT, with TBO, on dual-species biofilms of C. albicans and C. krusei using different culture mediums, RPMI-1640 and Sabouraud-dextrose broth (SDB) to produce biofilms presenting different C. albicans/C. krusei ratio. Biofilms formed using RPMI-1640 presented a higher C. albicans/C. krusei ratio, however, biofilms formed using SDB presented a predominance of C. krusei. The metabolic activity of biofilms produced using RPMI-1640 was inhibited by aP (∼40%), while biofilms produced using SDB were not affected by aPDT. In addition, biofilm biomass was reduced in biofilms produced using RPMI-1640 and treated with aPDT (∼20%). The results demonstrated that aPDT reduces C. albicans development in dual-species biofilms with C. krusei. However, no effect could be observed on C. krusei, demonstrating that C. krusei, when present in the structure of dual-species biofilms can be resistant to aPDT.

Antifungal Biofilm Inhibitory Effects of Combinations of Diclofenac and Essential Oils

Systemic fungal infections have risen in recent decades and most of them are caused by Candida species, which are becoming increasingly resistant to conventional antifungal drugs. Biofilm production has been considered the most common growth form of Candida cells and is associated with a high level of antifungal resistance. At present, international research reports on the antifungal activity of non-traditional antimicrobial drugs and their potential use against life-threatening resistant fungal infections. Indeed, drug repurposing has led to the consideration of well-known compounds as a last-line therapy. The goal of this work is to evaluate the potential synergistic antifungal biofilm activity of new combinations between diclofenac sodium salt (DSS), a widely used non-steroidal anti-inflammatory drug (NSAID), with the essential oils (EOs) of Mentha piperita, Pelargonium graveolens, and Melaleuca alternifolia, whose antifungal activity has been well documented over the years. The in vitro antifungal activity of DSS and EOs was determined on different Candida strains. Susceptibility testing and the synergism of DSS and EOs versus biofilm cells was performed by using the broth microdilution assay and checkerboard methods. Minimum inhibitory concentrations (sMIC50) of DSS alone ranged from 1.25 to 2.05 mg/mL for all the strains considered. These values significantly decreased when the drug was used in combination with the EOs. The fractional inhibitory concentration index (FICI) was lower than 0.5 for almost all the associations, thus indicating a significant synergism, particularly for the DSS-Pelargonium graveolens combination towards the Candida strains examined. These preliminary results show that the combination of the EOs with DSS improves the antifungal activity on all the tested Candida strains, significantly lowering the concentrations of the components used and thus allowing any toxic effects to be overcome.

Fungemia due to rare non-Candida yeasts between 2018 and 2021 in a Greek tertiary care university hospital

INTRODUCTION

Non-Candida yeasts, although rare, are increasingly encountered and recognized as a growing threat.

METHODS

Cases of bloodstream infections (BSIs) due to non-Candida yeasts (NCYs) during the last four years (2018-2021) are presented.

RESULTS

During the study period, 16 cases caused by non-Candida yeasts out of 400 cases of yeast BSIs were recorded, corresponding to an incidence of 4%. Yeasts that were isolated included Cryptococcus spp (4 isolates-25%), Rhodotorula mucilaginosa (2 isolates-12.5%), Trichosporon asahii (7 isolates-43.75%) and Saccharomyces cerevisiae (3 isolates-18.75%). Predisposing factors involved mostly hematological malignancies, long term hospitalization or major surgical interventions. Most isolates, 15 out of 16 were susceptible to amphotericin B. Voriconazole was the most active azole in vitro. All isolates, except Saccharomyces spp., were resistant to echinocandins.

DISCUSSION

Early recognition of rare yeasts as causative agents of BSIs and prompt initiation of appropriate treatment based on current guidelines and expertise remain crucial in efficient patient management.

Evaluation of the polyphenolic profile of native Ecuadorian stingless bee honeys (Tribe: Meliponini) and their antibiofilm activity on susceptible and multidrug-resistant pathogens: An exploratory analysis

Biofilms are associated with infections that are resistant to conventional therapies, contributing to the antimicrobial resistance crisis. The need for alternative approaches against biofilms is well-known. Although natural products like stingless bee honeys (tribe: Meliponini) constitute an alternative treatment, much is still unknown. Our main goal was to evaluate the antibiofilm activity of stingless bee honey samples against multidrug-resistant (MDR) pathogens through biomass assays, fluorescence (cell count and viability), and scanning electron (structural composition) microscopy. We analyzed thirty-five honey samples at 15% (v/v) produced by ten different stingless bee species (Cephalotrigona sp., Melipona sp., M. cramptoni, M. fuscopilosa, M. grandis, M. indecisa, M. mimetica, M. nigrifacies, Scaptotrigona problanca, and Tetragonisca angustula) from five provinces of Ecuador (Tungurahua, Pastaza, El Oro, Los Ríos, and Loja) against 24-h biofilms of Staphylococcus aureus, Klebsiella pneumoniae, Candida albicans, and Candida tropicalis. The present honey set belonged to our previous study, where the samples were collected in 2018-2019 and their physicochemical parameters, chemical composition, mineral elements, and minimal inhibitory concentration (MIC) were screened. However, the polyphenolic profile and their antibiofilm activity on susceptible and multidrug-resistant pathogens were still unknown. According to polyphenolic profile of the honey samples, significant differences were observed according to their geographical origin in terms of the qualitative profiles. The five best honey samples (OR24.1, LR34, LO40, LO48, and LO53) belonging to S. problanca, Melipona sp., and M. indecisa were selected for further analysis due to their high biomass reduction values, identification of the stingless bee specimens, and previously reported physicochemical parameters. This subset of honey samples showed a range of 63-80% biofilm inhibition through biomass assays. Fluorescence microscopy (FM) analysis evidenced statistical log reduction in the cell count of honey-treated samples in all pathogens (P <0.05), except for S. aureus ATCC 25923. Concerning cell viability, C. tropicalis, K. pneumoniae ATCC 33495, and K. pneumoniae KPC significantly decreased (P <0.01) by 21.67, 25.69, and 45.62%, respectively. Finally, scanning electron microscopy (SEM) analysis demonstrated structural biofilm disruption through cell morphological parameters (such as area, size, and form). In relation to their polyphenolic profile, medioresinol was only found in the honey of Loja, while scopoletin, kaempferol, and quercetin were only identified in honey of Los Rios, and dihydrocaffeic and dihydroxyphenylacetic acids were only detected in honey of El Oro. All the five honey samples showed dihydrocoumaroylhexose, luteolin, and kaempferol rutinoside. To the authors' best knowledge, this is the first study to analyze stingless bees honey-treated biofilms of susceptible and/or MDR strains of S. aureus, K. pneumoniae, and Candida species.

Microbiological evaluation in invisible aligner chemical cleaning methods against Candida albicans and Streptococcus mutans

INTRODUCTION

This study aimed to assess the efficacy of chemical agents in removing Candida albicans and Streptococcus mutans biofilm from invisible aligners.

METHODS

The samples were made of EX30 Invisalign trays, biofilm was cultured by standardized suspensions of C. albicans ATCC strain and S. mutans clinical strain on the sample. The treatments used were 0.5% sodium hypochlorite (NaClO) (20 minutes), 1% NaClO (10 minutes), chlorhexidine (5 minutes), peroxide (15 minutes), and orthophosphoric acid (15 seconds). The control group received phosphate-buffered saline for 10 minutes. The colony-forming units per milliliter of each microorganism were determined by serial dilutions seeded in plates with selective culture mediums for each one. Data were analyzed by the Kruskal-Wallis and Conover-Iman tests at an α of 0.05.

RESULTS

For the C. albicans biofilm group, the control group had 9.7 Log10 of microorganism growth, and all treatment groups had statistically significant biofilm reduction, in which chlorhexidine presented the highest inhibition of 3 Log10, followed by alkaline peroxide and orthophosphoric acid both with 2.6 Log10, 1% NaClO (2.5 Log10), and 0.5% NaClO (2 Log10). As for S. mutans, the control group had 8.9 Log10 of growth, and a total microorganism inhibition was reached by chlorhexidine, 1% NaClO, and orthophosphoric acid, whereas alkaline peroxide inhibited growth to 7.9 Log10 and 0.5% NaClO 5.1 Log10.

CONCLUSIONS

Within the limitations, chlorhexidine and orthophosphoric acid had greater efficacy in both biofilms. In addition, 1% NaClO and alkaline peroxide also had significant effects; therefore, their incorporation aligners disinfection protocols are valid.

Combined Application of Antisense Oligomers to Control Transcription Factors of Candida albicans Biofilm Formation

Antisense oligomers (ASOs) have been little exploited to control determinants of Candida albicans virulence. Biofilm formation is an important virulence factor of C. albicans, that is regulated by a complex network of transcription factors (such as EFG1, BRG1 and ROB1). Thus, the main goal of this work was to project ASOs, based on the 2'-OMethyl chemical modification, to target BRG1 and ROB1 mRNA and to validate its application either alone or in combination with the EFG1 mRNA target, to reduce C. albicans biofilm formation. The ability of ASOs to control gene expression was evaluate by qRT-PCR. The effect on biofilm formation was determined by the total biomass quantification, and simultaneously the carbohydrates and proteins reduction on extracellular matrix. It was verified that all the oligomers were able to reduce the levels of gene expression and the ability of C. albicans to form biofilms. Furthermore, the combined application of the cocktail of ASOs enhances the inhibition of C. albicans biofilm formation, minimizing biofilm thickness by reducing the quantity of matrix content (protein and carbohydrate). So, our work confirms that ASOs are useful tools for research and therapeutic development on the control of Candida species biofilm formation.

Candida albicans antibiofilm molecules: analysis based on inhibition and eradication studies

Biofilms are communities of microbial cells surrounded by an extracellular polysaccharide matrix, recognized as a fungal source for local and systemic infections and less susceptible to antifungal drugs. Thus, treatment of biofilm-related Candida spp. infections with popular antifungals such as fluconazole is limited and species-dependent and alternatively demands the use of expensive and high toxic drugs. In this sense, molecules with antibiofilm activity have been studied but without care regarding the use of important criteria such as antibiofilm concentration lower than antifungal concentration when considering the process of inhibition of formation and concentrations equal to or lower than 300 µM. Therefore, this review tries to gather the most promising molecules regarding the activity against the C. albicans biofilm described in the last 10 years, considering the activity of inhibition and eradication. From January 2011 to July 2021, articles were searched on Scopus, PubMed, and Science Direct, combining the keywords "antibiofilm," "candida albicans," "compound," and "molecule" with AND and OR operators. After 3 phases of selection, 21 articles describing 42 molecules were discussed in the review. Most of them were more promising for the inhibition of biofilm formation, with SM21 (24) being an interesting molecule for presenting inhibitory and eradication activity in biofilms with 24 and 48 h, as well as alizarin (26) and chrysazine (27), with concentrations well below the antifungal concentration. Despite the detection of these molecules and the attempts to determine the mechanisms of action by microscopic analysis and gene expression, no specific target has been determined. Thus, a gap is signaled, requiring further studies such as proteomic analyses to clarify it.

Sertraline has in vitro activity against both mature and forming biofilms of different Candida species

Candida spp. infections are a serious health problem, especially in patients with risk factors. The acquisition of resistance, often associated with biofilm production, makes treatment more difficult due to the reduced effectiveness of available antifungals. Drug repurposing is a good alternative for the treatment of infections by Candida spp. biofilms. The present study evaluated the in vitro antibiofilm activity of sertraline in reducing the cell viability of forming and matured biofilms, in addition to elucidating whether effective concentrations are safe. Sertraline reduced biofilm cell viability by more than 80 % for all Candida species tested, acting at low and safe concentrations, both on mature biofilm and in preventing its formation, even the one with highest virulence. Its preventive mechanism seemed to be related to binding with ALS3. These data indicate that sertraline is a promising drug with anticandidal biofilm potential in safe doses. However, further studies are needed to elucidate the antibiofilm mechanism and possible application of pharmaceutical forms.

The Landscape of Gene Expression during Hyperfilamentous Biofilm Development in Oral Candida albicans Isolated from a Lung Cancer Patient

The filamentation ability of Candida albicans represents one of the main virulence factors allowing for host tissue penetration and biofilm formation. The aim of this paper was to study the genetic background of the hyperfilamentous biofilm development in vitro in C. albicans isolated from the oral cavity of a lung cancer patient. Analyzed C. albicans isolates (CA1, CA2, CA3) were chosen based on their different structures of mature biofilm. The CA3 isolate possessing hyperfilamentation properties and forming high biofilm was compared with CA1 and CA2 isolates exhibiting low or average biofilm-forming ability, respectively. The detailed biofilm organization was studied with the use of confocal scanning laser microscopy. The whole transcriptome analysis was conducted during three stages of biofilm development (24 h, 48 h, 72 h). In contrast to CA1 and/or CA2 isolate, the CA3 isolate was characterized by a significant upregulation of genes encoding for cell wall proteins (HWP1, PGA13, PGA44, ALS3) and candidalysin (ECE1), as well as being involved in iron metabolism (FRE1, ALS3), sulfur metabolism (HAL21), the degradation of aromatic compounds (HQD2), and membrane transport (DIP5, PHO89, TNA1). In contrast, some genes (SCW11, FGR41, RBE1) in the CA3 were downregulated. We also observed the overexpression of a few genes over time-mainly FRE1, ATX1, CSA2 involved in iron metabolism. This is the first insight into the potential function of multiple genes in the hyperfilamentous biofilm formation in C. albicans, primarily isolated from host tissue, which may have an important clinical impact on cancer patients. Moreover, the presented data can lay the foundation for further research on novel pathogen-specific targets for antifungal drugs.

Evaluating the effects of zeolitic imidazolate framework and Eremostachys binalodensis extract on Candida albicans and Streptococcus mutans biofilms

Biofilms represent longstanding challenges to oral health care. Candida albicans and Streptococcus mutans are the common pathogens forming biofilms. The growing resistance to and the adverse effects of antibiotics limit their usage and raise the need for novel approaches. Herbal extracts have emerged as efficient choices with lower costs and fewer adverse effects. Metal frameworks have captivated interest due to their high surface area, special biocompatibility, and non-toxicity. The effects of zeolitic imidazolate frameworks/layered double hydroxide (ZIF/LDH) on fungal infections and the potential effects of Eremostachys binalodensis on bacteria encouraged the researchers to evaluate the effect of ZIF/LDH, E. binalodensis, and their combination on C. albicans and S. mutans biofilms. ZIF/LDH nanocomposite was synthesized and characterized using scanning electron microscopy, Fourier transform infrared spectra, and X-ray diffraction to assess morphology and chemical structure. Methanol extracts of the areal parts of E. binalodensis were obtained by Soxhlet extraction. The microdilution tests and biofilm crystal violet staining were applied. Concentrations of 2.048 and 4.096 mg/ml E. binalodensis prevented C. albicans and S. mutans biofilm formation. The combination of ZIF/LDH + E. binalodensis prevented C. albicans and S. mutans biofilm formation. This research suggests the use of E. binalodensis-loaded ZIF/LDH nanocomposites for removing biofilms.

A protocol for ultrastructural study of Candida albicans biofilm using transmission electron microscopy

This protocol describes how to analyze C.albicans biofilm using transmission electron microscopy. We present two approaches to observe the ultrastructure of fungal cells within unperturbed biofilms, as well as an immunogold labeling procedure. This approach maintains the architecture of the fungal biofilm close to its native state by growing C. albicans biofilm on a plastic surface. After the freeze substitution procedure, classical transmission electron microscopy or electron tomography will allow the ultrastructural analysis of the microbial community.

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A protocol to study the ultrastructure of unperturbed biofilms of C. albicans

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Suitable for contrasting, immunogold labeling, and electron tomography

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Maintain cellular junctions between fungal cells from the microbial community

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The protocol may be applicable to other microorganisms able to form biofilms

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Evaluation of the biofilm life cycle between Candida albicans and Candida tropicalis

Candida tropicalis is an emergent pathogen with a high rate of mortality associated with its biofilm formation. Biofilm formation has important repercussions on the public health system. However, little is still known about its biofilm life cycle. The present study analyzed the biofilm life cycle of Candida albicans and C. tropicalis during various timepoints (24, 48, 72, and 96 h) through biomass assays, colony-forming unit (CFU) counting, and epifluorescence and scanning electron microscopies. Our results showed a significant difference between C. albicans and C. tropicalis biofilms in each biomass and viability assay. All-time samples in the biomass and viability assays confirmed statistical differences between the Candida species through pairwise Wilcoxon tests (p < 0.05). C. albicans demonstrated a lower biomass growth but reached nearly the same level of C. tropicalis biomass at 96 h, while the CFU counting assays exhibited a superior number of viable cells within the C. tropicalis biofilm. Statistical differences were also found between C. albicans and C. tropicalis biofilms from 48- and 72-h microscopies, demonstrating C. tropicalis with a higher number of total cells within biofilms and C. albicans cells with a superior cell area and higher matrix production. Therefore, the present study proved the higher biofilm production of C. tropicalis.

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

Purpose

Methods

Results

Conclusion

Petrositis caused by fluconazole-resistant candida: case report and literature review

Background

Petrositis is a rare and fatal complication associated with otitis media. It is most likely caused by bacterial infections, but in some cases it is caused by fungal infections.

Case study

The case in this report is associated with fungal petrositis. The clinical symptoms are: ear pain from chronic otitis media, severe headache, peripheral facial palsy and diplopia. The case was finally confirmed through imaging of middle ear, bacterial culture, pathology, and blood Metagenomic next-generation sequencing (mNGS) test. The patient was treated with sensitive antifungal drugs.

Conclusion

Drug treatment is conservative but efficient method in this case. mNGS can provide pathogenic reference, when antibiotic is not efficient enough for fungal infections or drug-resistant fungal infections cases. This allows we to adjust drug use for the treatment.

JcTI-PepI, a synthetic peptide bioinspired in the trypsin inhibitor from Jatropha curcas, presents potent inhibitory activity against C. krusei, a neglected pathogen

Antimicrobial resistance has been increasing globally, posing a global public health risk. It has prompted the scientific community to look for alternatives to traditional drugs. Antimicrobial Peptides (AMPs) have stood out in this context because they have the potential to control infectious diseases while causing no or little harm to mammalian cells. In the present study, three peptides, JcTI-PepI, JcTI-PepII, and JcTI-PepIII, were designed and tested for antimicrobial activity based on the primary sequence of JcTI-I, a 2S albumin with trypsin inhibitory activity from Jatropha curcas. JcTI-PepI strongly inhibited C. krusei growth, and it caused severe disruptions in cellular processes and cell morphology. C. krusei cells treated with JcTI-PepI showed indicative of membrane permeabilization and overproduction of Reactive Oxygen Species. Moreover, the yeast's ability to acidify the medium was severely compromised. JcTI-PepI was also effective against pre-formed biofilm and did not harm human erythrocytes and Vero cells. Overall, these characteristics indicate that JcTI-PepI is both safe and effective against C. krusei, an intrinsically resistant strain that causes serious health problems and is frequently overlooked. It implies that this peptide has a high potential for use as a new antimicrobial agent in the future.

Microbially-derived cocktail of carbohydrases as an anti-biofouling agents: a 'green approach'

Enzymes, also known as biocatalysts, display vital properties like high substrate specificity, an eco-friendly nature, low energy inputs, and cost-effectiveness. Among their numerous known applications, enzymes that can target biofilms or their components are increasingly being investigated for their anti-biofouling action, particularly in healthcare, food manufacturing units and environmental applications. Enzymes can target biofilms at different levels like during the attachment of microorganisms, formation of exopolymeric substances (EPS), and their disruption thereafter. In this regard, a consortium of carbohydrases that can target heterogeneous polysaccharides present in the EPS matrix may provide an effective alternative to conventional chemical anti-biofouling methods. Further, for complete annihilation of biofilms, enzymes can be used alone or in conjunction with other antimicrobial agents. Enzymes hold the promise to replace the conventional methods with greener, more economical, and more efficient alternatives. The present article explores the potential and future perspectives of using carbohydrases as effective anti-biofilm agents.

Enhancing effect of chitosan on methylene blue-mediated photodynamic therapy against C. albicans: a study in planktonic growth, biofilms, and persister cells

Chitosan (CS) is a natural polymer extracted from the exoskeleton of crustaceans. Due to its cationic structure, CS has been studied as a possible enhancer of antimicrobial photodynamic therapy (aPDT). The objective was to evaluate the association of CS with methylene blue (MB)-mediated aPDT on Candida albicans, investigating its effects on planktonic growth, biofilms, and cells persistent to fluconazole. The ability of CS to interfere with MB absorption by Candida cells was also evaluated. For the assays, planktonic cells of C. albicans were cultivated for 24 h, and the biofilms were formed for 48 h. For the induction of persister cells, C. albicans was cultivated with high concentration of fluconazole for 48 h. Treatments were performed with MB, CS or MB+CS, followed by irradiation with LED (660 nm). As results, aPDT with MB (300 µm) reduced the planktonic cells by 1.6 log10 CFU, while the MB+CS association led to a reduction of 4.8 log10 CFU. For aPDT in biofilms, there was a microbial reduction of 2.9 log10 CFU for the treatment with MB (600 µm) and 5.3 log10 CFU for MB+CS. In relation to persister cells, the fungal reductions were 0.4 log10 CFU for MB and 1.5 log10 CFU for MB+CS. In the absorption assays, the penetration of MB into Candida cells was increased in the presence of CS. It was concluded that CS enhanced the antimicrobial activity of aPDT in planktonic growth, biofilms, and persister cells of C. albicans, probably by facilitating the penetration of MB into fungal cells.

Synergistic Antibiofilm Effects of Pseudolaric Acid A Combined with Fluconazole against Candida albicans via Inhibition of Adhesion and Yeast-To-Hypha Transition

Candida albicans biofilms are resistant to several clinical antifungal agents. Thus, it is necessary to develop new antibiofilm intervention measures. Pseudolaric acid A (PAA), a diterpenoid mainly derived from the pine bark of Pseudolarix kaempferi, has been reported to have an inhibitory effect on C. albicans. The primary aim of the current study was to investigate the antibiofilm effect of PAA when combined with fluconazole (FLC) and explore the underlying mechanisms. Biofilm activity was assessed by tetrazolium {XTT [2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide salt]} reduction assays. PAA (4 μg/mL) combined with FLC (0.5 μg/mL) significantly inhibited early, developmental, and mature biofilm formation compared with the effect of PAA or FLC alone (P < 0.05). Furthermore, PAA (4 μg/mL) combined with FLC (0.5 μg/mL) produced a 56% reduction in C. albicans biofilm adhesion. The combination of PAA (4 μg/mL) and FLC (0.5 μg/mL) also performed well in inhibiting yeast-to-hypha transition. Transcriptome analysis using RNA sequencing and quantitative reverse transcription PCR indicated that the PAA-FLC combination treatment produced a strong synergistic inhibitory effect on the expression of genes involved in adhesion (ALS1, ALS4, and ALS2) and yeast-to-hypha transition (ECE1, PRA1, and TEC1). Notably, PAA, rather than FLC, may have a primary role in suppressing the expression of ALS1. In conclusion, these findings demonstrate, for the first time, that the combination of PAA and FLC has an improved antibiofilm effect against the formation of C. albicans biofilms by inhibiting adhesion and yeast-to-hypha transition; this may provide a novel therapeutic strategy for treating C. albicans biofilm-associated infection.

IMPORTANCE Biofilms are the primary cause of antibiotic-resistant candida infections associated with medical implants and devices worldwide. Treating biofilm-associated infections is a challenge for clinicians because these infections are intractable and persistent. Candida albicans readily forms extensive biofilms on the surface of medical implants and mucosa. In this study, we demonstrated, for the first time, an inhibitory effect of pseudolaric acid A alone and in combination with fluconazole on C. albicans biofilms. Moreover, pseudolaric acid A in combination with fluconazole exerted an antibiofilm effect through multiple pathways, including inhibition of yeast-to-hypha transition and adhesion. This research not only provides new insights into the synergistic mechanisms of antifungal drug combinations but also brings new possibilities for addressing C. albicans drug resistance.

Ethyl Acetate Fraction of Punica granatum and Its Galloyl-HHDP-Glucose Compound, Alone or in Combination with Fluconazole, Have Antifungal and Antivirulence Properties against Candida spp

Candidiasis is the most common fungal infection among immunocompromised patients. Its treatment includes the use of antifungals, which poses limitations such as toxicity and fungal resistance. Plant-derived extracts, such as Punica granatum, have been reported to have antimicrobial activity, but their antifungal effects are still unknown. We aimed to evaluate the antifungal and antiviral potential of the ethyl acetate fraction of P. granatum (PgEA) and its isolated compound galloyl-hexahydroxydiphenoyl-glucose (G-HHDP-G) against Candida spp. In silico analyses predicted the biological activity of G-HHDP-G. The minimum inhibitory concentrations (MIC) of PgEA and G-HHDP-G, and their effects on biofilm formation, preformed biofilms, and phospholipase production were determined. In silico analysis showed that G-HHDP-G has antifungal and hepatoprotective effects. An in vitro assay confirmed the antifungal effects of PgEA and G-HHDP-G, with MIC in the ranges of 31.25–250 μg/mL and 31.25 ≥ 500 μg/mL, respectively. G-HHDP-G and PgEA synergistically worked with fluconazole against planktonic cells. The substances showed antibiofilm action, alone or in combination with fluconazole, and interfered with phospholipase production. The antifungal and antibiofilm actions of PgEA and G-HHDP-G, alone or in combination with fluconazole, in addition to their effects on reducing Candida phospholipase production, identify them as promising candidates for therapeutics.

Antifungal activity of 2-Chloro-N-phenylacetamide, docking and molecular dynamics studies against clinical isolates of Candida tropicalis and Candida parapsilosis

AIMS

This study evaluated the antifungal, antibiofilm, and molecular docking of 2-Chloro-N-phenylacetamide against clinical isolates of Candida tropicalis and Candida parapsilosis.

METHODS AND RESULTS

MIC of the test drugs was determined by microdilution. A1Cl obtained MIC values ranging from 16 and 256 μg/mL. Fluconazole MIC ranging from 16 and 512 μg/mL. MIC of A1Cl showed fungicide activity, emphasizing the solid antifungal potential of this drug. An association study was performed with A1Cl and fluconazole (checkerboard), revealing indifference by decreasing. Thus, we conducted this study using A1Cl isolated. In the micromorphological assay, the test drugs reduced the production of virulence structures compared to the control (concentration-dependent effect). A1Cl inhibited in vitro biofilm formation at all concentrations tested (1/4MIC to 8xMIC) (p<0.05) and reduced mature biofilm biomass (p<0.05) against C. tropicalis and C. parapsilosis. In the ex vivo biofilm susceptibility testing (human nails fragments), A1Cl inhibited biofilm formation and reduced mature biofilm biomass (p<0.05) more than 50% at MIC. Fluconazole had a similar effect at 4xMIC. In silico studies suggest that the mechanism of antifungal activity of A1Cl involves the inhibition of the enzyme dihydrofolate reductase rather than geranylgeranyltransferase-I.

CONCLUSIONS

The results suggest that A1Cl is a promising antifungal agent. Furthermore, this activity is related to attenuation of expression of virulence factors and antibiofilm effects against C. tropicalis and C. parapsilosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study provides the first evidence that A1Cl, a novel synthetic drug, has fungicidal effects against C. tropicalis and C. parapsilosis. Furthermore, in vitro and ex vivo biofilms assays have demonstrated the potential antibiofilm of A1Cl. The mechanism of action involves inhibiting the enzyme dihydrofolate reductase, which was supported by in silico analyses. Therefore, this potential can be explored as a therapeutic alternative for onychomycosis and, at the same time, contribute to decreasing the resistance of clinical isolates of C. tropicalis and C. parapsilosis.

Origanum vulgare L. essential oil inhibits virulence patterns of Candida spp. and potentiates the effects of fluconazole and nystatin in vitro

Background

Recurrence and resistance of Candida spp. infections is associated with the ability of these microorganisms to present several virulence patterns such as morphogenesis, adhesion, and biofilm formation. In the search for agents with antivirulence activity, essential oils could represent a strategy to act against biofilms and to potentiate antifungal drugs.

Objective

To evaluate the antivirulence effect of Origanum vulgare L. essential oil (O-EO) against Candida spp. and to potentiate the effect of fluconazole and nystatin.

Methods

The effect of O-EO was evaluated on ATCC reference strains of C. albicans and non-albicans Candida species. Minimum inhibitory concentration (MIC) was determined through broth microdilution assay. Adhesion to microplates was determined by crystal violet (CV) assay. An adapted scratch assay in 24-well was used to determine the effect of essential oil on biofilms proliferation. Viability of biofilms was evaluated by MTT reduction assay and through a checkerboard assay we determined if O-EO could act synergistically with fluconazole and nystatin.

Results

MIC for C. albicans ATCC-90029 and ATCC-10231 was 0.01 mg/L and 0.97 mg/L, respectively. For non-albicans Candida strains MIC values were 2.6 mg/L for C. dubliniensis ATCC-CD36 and 5.3 mg/L for C. krusei ATCC-6258. By using these concentrations, O-EO inhibited morphogenesis, adhesion, and proliferation at least by 50% for the strains assayed. In formed biofilms O-EO decreased viability in ATCC 90029 and ATCC 10231 strains (IC50 7.4 and 2.8 mg/L respectively). Finally, we show that O-EO interacted synergistically with fluconazole and nystatin.

Conclusions

This study demonstrate that O-EO could be considered to improve the antifungal treatment against Candida spp.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03518-z.

Production and Isolation of the Candida Species Biofilm Extracellular Matrix

The extracellular matrix (ECM) is a dynamic structure comprising of all four classes of macromolecules. In the biofilm setting, this matrix is key to the survival of microbial communities by conferring to biofilms both structural integrity and protection against diverse environmental insults. In Candida spp., this matrix contributes to pathogenesis by conferring to biofilms both drug resistance and protection against immune attack. Understanding the biochemical nature of the matrix and its individual components is critical to the development of novel diagnostics and antifungal strategies against persistent Candida biofilm infections. Therefore, efficient methods for ECM isolation are required. The two matrix isolation protocols described herein are adapted for both small- and large-scale isolation of biofilm matrix. Both procedures involve seeding of biofilms in either 6-well plates or large-surface-area roller bottles, followed by cell adhesion and biofilm maturation for 2 days with continuous motion. In both cases, the matrix is separated from the biomass via sonication, a step which gently and effectively removes the matrix without disturbing the fungal cell wall. The large-scale protocol includes additional filtration, lyophilization, and dialysis steps to yield purified matrix material sufficient for numerous biochemical, structural, and functional assays. Small-scale isolation yields enough matrix for gas chromatography (GC), total carbohydrate quantification via the phenol-sulfuric acid method, and total protein quantification via the bicinchoninic acid (BCA) assay. Large-scale isolation yields enough matrix to perform NMR spectroscopy, liquid chromatography, mass spectrometry, and nucleic acid sequencing. These protocols have been adapted for use in Candida species but may be adapted for other biofilm-forming fungal species and bacteria.

Quantification of the Adhesion Strength of Candida albicans to Tooth Enamel

Caries is one of the most prevalent diseases worldwide, which is caused by the degradation of the tooth enamel surface. In earlier research the opportunistic pathogen Candida albicans has been associated with the formation of caries in children. Colonization of teeth by C. albicans starts with the initial adhesion of individual yeast cells to the tooth enamel surface. In this study, we visualized the initial colonization of C. albicans yeast cells on pellicle-covered enamel by scanning electron microscopy. To quantitatively unravel the initial adhesion strength, we applied fluidic force microscopy-based single-cell force spectroscopy to examine the key adhesion parameters adhesion force, rupture length and de-adhesion work. We analyzed single saliva-treated or untreated yeast cells on tooth enamel specimens with or without salivary pellicle. Under all tested conditions, adhesion forces in the lower nanonewton range were determined. Furthermore, we have found that all adhesion parameters were enhanced on the pellicle-covered compared to the uncovered enamel. Our data suggest that initial adhesion occurs through a strong interaction between yeast cell wall-associated adhesins and the salivary pellicle. Future SCFS studies may show whether specific management of the salivary pellicle reduces the adhesion of C. albicans on teeth and thus contributes to caries prophylaxis.

Fungal Biofilms as a Valuable Target for the Discovery of Natural Products That Cope with the Resistance of Medically Important Fungi-Latest Findings

The development of new antifungal agents that target biofilms is an urgent need. Natural products, mainly from the plant kingdom, represent an invaluable source of these entities. The present review provides an update (2017-May 2021) on the available information on essential oils, propolis, extracts from plants, algae, lichens and microorganisms, compounds from different natural sources and nanosystems containing natural products with the capacity to in vitro or in vivo modulate fungal biofilms. The search yielded 42 articles; seven involved essential oils, two Brazilian propolis, six plant extracts and one of each, extracts from lichens and algae/cyanobacteria. Twenty articles deal with the antibiofilm effect of pure natural compounds, with 10 of them including studies of the mechanism of action and five dealing with natural compounds included in nanosystems. Thirty-seven manuscripts evaluated Candida spp. biofilms and two tested Fusarium and Cryptococcus spp. Only one manuscript involved Aspergillus fumigatus. From the data presented here, it is clear that the search of natural products with activity against fungal biofilms has been a highly active area of research in recent years. However, it also reveals the necessity of deepening the studies by (i) evaluating the effect of natural products on biofilms formed by the newly emerged and worrisome health-care associated fungi, C. auris, as well as on other non-albicans Candida spp., Cryptococcus sp. and filamentous fungi; (ii) elucidating the mechanisms of action of the most active natural products; (iii) increasing the in vivo testing.

Polyhydroxyalkanoate/Antifungal Polyene Formulations with Monomeric Hydroxyalkanoic Acids for Improved Antifungal Efficiency

Novel biodegradable and biocompatible formulations of "old" but "gold" drugs such as nystatin (Nys) and amphotericin B (AmB) were made using a biopolymer as a matrix. Medium chain length polyhydroxyalkanoates (mcl-PHA) were used to formulate both polyenes (Nys and AmB) in the form of films (~50 µm). Thermal properties and stability of the materials were not significantly altered by the incorporation of polyenes in mcl-PHA, but polyene containing materials were more hydrophobic. These formulations were tested in vitro against a panel of pathogenic fungi and for antibiofilm properties. The films containing 0.1 to 2 weight % polyenes showed good activity and sustained polyene release for up to 4 days. A PHA monomer, namely 3-hydroxydecanoic acid (C10-OH), was added to the films to achieve an enhanced synergistic effect with polyenes against fungal growth. Mcl-PHA based polyene formulations showed excellent growth inhibitory activity against both Candida yeasts (C. albicans ATCC 1023, C. albicans SC5314 (ATCC MYA-2876), C. parapsilosis ATCC 22019) and filamentous fungi (Aspergillus fumigatus ATCC 13073; Trichophyton mentagrophytes ATCC 9533, Microsporum gypseum ATCC 24102). All antifungal PHA film preparations prevented the formation of a C. albicans biofilm, while they were not efficient in eradication of mature biofilms, rendering them suitable for the transdermal application or as coatings of implants.

Prevalence of vulvovaginal candidiasis in Brazil: a systematic review

Vulvovaginal candidiasis (CVV) is a condition whose signs and symptoms are related to inflammation caused by Candida spp infection. It is the second leading cause of vaginitis in the world, representing a public health problem. The present systematic review comes with the proposal of analyze and identify the available evidence on CVV prevalence in Brazil, pointing out its variability by regions. For this, a systematic literature review was carried out with meta-analysis of cross-sectional and cohort studies, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) guide recommendations, and was registered in the International Prospective Register of Systematic Reviews (PROSPERO 2020 CRD42020181695). The databases used for survey were LILACS, Scielo, Scopus, PUBMED, Web of Science and CINAHL. Fifteen studies were selected to estimate CVV prevalence in the Brazilian territory. South and Southeast regions have higher prevalences than the North and Northeast regions, no data were found for the Midwest region. The estimated prevalence for Brazil is 18%, however, it is suggested that this number is higher due to underreporting and the presence of asymptomatic cases. Therefore, new epidemiological studies are recommended throughout Brazil, to elucidate the profile of this disease in the country, in addition to assisting in the elaboration of an appropriate prevention plan by state.

LAY ABSTRACT

Data found in the literature regarding the epidemiological profile of VVC in Brazil are obsolete and incomplete, so the present systematic review has the proposal to analyze and identify the evidence on VVC prevalence in Brazil. The estimated prevalence is 18%, however, this number can be higher.

Whole slide imaging is a high-throughput method to assess Candida biofilm formation

New strategies that enable fast and accurate visualization of Candida biofilms are necessary to better study their structure and response to antifungals agents. Here, we applied whole slide imaging (WSI) to study biofilm formation of Candida species. Three relevant biofilm-forming Candida species (C. albicans ATCC 10231, C. glabrata ATCC 2001, and C. tropicalis ATCC 750) were cultivated on glass coverslips both in presence and absence of widely used antifungals. Accumulated biofilms were stained with fluorescent markers and scanned in both bright-field and fluorescence modes using a WSI digital scanner. WSI enabled clear assessment of both size and structural features of Candida biofilms. Quantitative analyses readily detected reductions in biofilm-covered surface area upon antifungal exposure. Furthermore, we show that the overall biofilm growth can be adequately assessed across both bright-field and fluorescence modes. At the single-cell level, WSI proved adequate, as morphometric parameters evaluated with WSI did not differ significantly from those obtained with scanning electron microscopy, considered as golden standard at single-cell resolution. Thus, WSI allows for reliable visualization of Candida biofilms enabling both large-scale growth assessment and morphometric characterization of single-cell features, making it an important addition to the available microscopic toolset to image and analyse fungal biofilm growth.

StuA-Regulated Processes in the Dermatophyte Trichophyton rubrum: Transcription Profile, Cell-Cell Adhesion, and Immunomodulation

Fungal infections represent a significant concern worldwide, contributing to human morbidity and mortality. Dermatophyte infections are among the most significant mycoses, and Trichophyton rubrum appears to be the principal causative agent. Thus, an understanding of its pathophysiology is urgently required. Several lines of evidence have demonstrated that the APSES family of transcription factors (Asm1p, Phd1p, Sok2p, Efg1p, and StuA) is an important point of vulnerability in fungal pathogens and a potential therapeutic target. These transcription factors are unique to fungi, contributing to cell differentiation and adaptation to environmental cues and virulence. It has recently been demonstrated that StuA plays a pleiotropic role in dermatophyte pathophysiology. It was suggested that it functions as a mediator of crosstalk between different pathways that ultimately contribute to adaptive responses and fungal-host interactions. The complex regulation of StuA and its interaction pathways are yet to be unveiled. Thus, this study aimed to gain a deeper understanding of StuA-regulated processes in T. rubrum by assessing global gene expression following growth on keratin or glucose sources. The data showed the involvement of StuA in biological processes related to central carbon metabolism and glycerol catabolism, reactive oxygen species metabolism, and cell wall construction. Changes in carbohydrate metabolism may be responsible for the significant alteration in cell wall pattern and consequently in cell-cell interaction and adhesion. Loss of StuA led to impaired biofilm production and promoted proinflammatory cytokine secretion in a human keratinocyte cell line. We also observed the StuA-dependent regulation of catalase genes. Altogether, these data demonstrate the multitude of regulatory targets of StuA with a critical role in central metabolism that may ultimately trigger a cascade of secondary effects with substantial impact on fungal physiology and virulence traits.

Design, synthesis and biological evaluation of a series of iron and copper chelating deferiprone derivatives as new agents active against Candida albicans

Candida albicans, in specific conditions, is responsible of severe invasive systemic candidiasis that are related to its ability to produce biofilm on biological and artificial surfaces. Many studies reported the role of iron in fungal growth and virulence and the ability of metal chelating agents to interfere with C. albicans metabolism, virulence and biofilm formation. Here we report the activity of 3-hydroxy-1,2-dimethyl-4(1H)-pyridinone (deferiprone) derivatives against C. albicans planktonic cells and biofilm. Some of the studied compounds (2b and 3b) were able to chelate Fe(III) and Cu(II), and showed an interesting activity on planktonic cells (MIC₅₀ of 32 μg/mL and 16 μg/mL respectively) and on biofilm formation (BMIC₅₀ of 32 μg/mL and 16 μg/mL respectively) in cultured ATCC 10,231C. albicans; this activity was reduced, in a concentration dependent way, by the addition of Fe(III) and Cu(II) to the culture media. Furthermore, the most active compound 3b showed a low toxicity on Galleria mellonella larvae.

Pathogenesis and Clinical Relevance of Candida Biofilms in Vulvovaginal Candidiasis

The ability of Candida spp. to form biofilms is crucial for its pathogenicity, and thus, it should be considered an important virulence factor in vulvovaginal candidiasis (VVC) and recurrent VVC (RVVC). Its ability to generate biofilms is multifactorial and is generally believed to depend on the site of infection, species and strain involved, and the microenvironment in which the infection develops. Therefore, both cell surface proteins, such as Hwp1, Als1, and Als2, and the cell wall-related protein, Sun41, play a critical role in the adhesion and virulence of the biofilm. Immunological and pharmacological approaches have identified the NLRP3 inflammasome as a crucial molecular factor contributing to host immunopathology. In this context, we have earlier shown that Candida albicans associated with hyphae-secreted aspartyl proteinases (specifically SAP4-6) contribute to the immunopathology of the disease. Transcriptome profiling has revealed that non-coding transcripts regulate protein synthesis post-transcriptionally, which is important for the growth of Candida spp. Other studies have employed RNA sequencing to identify differences in the 1,245 Candida genes involved in surface and invasive cellular metabolism regulation. In vitro systems allow the simultaneous processing of a large number of samples, making them an ideal screening technique for estimating various physicochemical parameters, testing the activity of antimicrobial agents, and analyzing genes involved in biofilm formation and regulation (in situ) in specific strains. Murine VVC models are used to study C. albicans infection, especially in trials of novel treatments and to understand the cause(s) for resistance to conventional therapeutics. This review on the clinical relevance of Candida biofilms in VVC focuses on important advances in its genomics, transcriptomics, and proteomics. Moreover, recent experiments on the influence of biofilm formation on VVC or RVVC pathogenesis in laboratory animals have been discussed. A clear elucidation of one of the pathogenesis mechanisms employed by Candida biofilms in vulvovaginal candidiasis and its applications in clinical practice represents the most significant contribution of this manuscript.

Oral Colonization by Candida Species in Patients with Multiple Sclerosis

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory demyelinating autoimmune disease that affects the central nervous system. Since immune system plays a key role in this disease, patients with MS can present higher risk of infections.

PURPOSE

This study aimed to investigate the prevalence of Candida spp. in the oral cavity of MS patients in relation to a control group METHODS: In total, 100 individuals were selected: 55 diagnosed with MS and 45 healthy individuals (control group). Saliva samples were collected and seeded in culture media selecting for Candida. Following an incubation period of 48 h, colony-forming units (CFU mL^-1) were counted and colonies were isolated for Candida species identification by multiplex PCR. The results were analysed by chi-squared and Mann-Whitney U statistical tests considering a significance level of 5%.

RESULTS

Candida spp. were confirmed in the oral cavity of 50.09% patients in the MS group and 35.55% individuals in the control group. In individuals positive for the growth of Candida spp., the median values of Candida colonies were 220 CFU mL^-1 for the MS group and 120 CFU mL^-1 for the control group. However, no statistically significant differences were observed between groups for both prevalence and CFU mL^-1 count. Of the Candida species identified, 73.91% were C. albicans, 21.73% C. glabrata, 2.17% C. tropicalis, and 2.17% C. krusei.

CONCLUSIONS

The colonization of Candida spp. in the oral cavity of individuals with multiple sclerosis was higher than in the control group; however these findings were not proven to be statistically significant.

Fungal Quorum-Sensing Molecules: A Review of Their Antifungal Effect against Candida Biofilms

The number of effective therapeutic strategies against biofilms is limited; development of novel therapies is urgently needed to treat a variety of biofilm-associated infections. Quorum sensing is a special form of microbial cell-to-cell communication that is responsible for the release of numerous extracellular molecules, whose concentration is proportional with cell density. Candida-secreted quorum-sensing molecules (i.e., farnesol and tyrosol) have a pivotal role in morphogenesis, biofilm formation, and virulence. Farnesol can mediate the hyphae-to-yeast transition, while tyrosol has the opposite effect of inducing transition from the yeast to hyphal form. A number of questions regarding Candida quorum sensing remain to be addressed; nevertheless, the literature shows that farnesol and tyrosol possess remarkable antifungal and anti-biofilm effect at supraphysiological concentration. Furthermore, previous in vitro and in vivo data suggest that they may have a potent adjuvant effect in combination with certain traditional antifungal agents. This review discusses the most promising farnesol- and tyrosol-based in vitro and in vivo results, which may be a foundation for future development of novel therapeutic strategies to combat Candida biofilms.