ARTICLE | doi:10.20944/preprints202103.0677.v1
Subject: Life Sciences, Biochemistry Keywords: Candida albicans; CD137; neutrophil; fungal clearance
Online: 29 March 2021 (09:47:02 CEST)
Invasive fungal infections by Candida albicans frequently cause mortality in immunocompromised patients. Neutrophils are particularly important for fungal clearance at the early phase of infections, yet little has been known regarding which surface receptor controls neutrophil phagocytic activities during systemic C. albicans infection. CD137, which is encoded by Tnfrsf9, belongs to the tumor necrosis receptor superfamily and has been shown to regulate neutrophils in Gram-positive bacterial infection. Here, we used genetic and immunological tools to probe the involvement of CD137 signaling in innate defense mechanisms against systemic C. albicans infection. We first found that Tnfrsf9-/- mice were susceptible to C. albicans infection, whereas injection of anti-CD137 agonistic antibody protected the host from infection, suggesting that CD137 signaling is indispensable for innate immunity against C. albicans infection. Priming of isolated neutrophils with anti-CD137 antibody promoted their phagocytic and fungicidal activities through phospholipase C. In addition, injection of anti-CD137 antibody significantly augmented restriction of fungal growth in Tnfrsf9-/- mice that received WT neutrophils. In conclusion, our results demonstrate that CD137 signaling contributes to defense mechanisms against systemic C. albicans infection by promoting rapid fungal clearance whereby harmful immunopathology-induced tissue injuries are minimalized.
ARTICLE | doi:10.20944/preprints202209.0424.v1
Subject: Medicine & Pharmacology, General Medical Research Keywords: Candida albicans; Lactobacillus species; biofilm; probiotics
Online: 27 September 2022 (12:34:41 CEST)
Antifungal agents are not always efficient in resolving vulvovaginal candidiasis (VVC), a common genital infection caused by overgrowth of Candida spp., including Candida albicans, or preventing recurrent infections. Although lactobacilli (which are dominant microorganisms constituting healthy human vaginal microbiota) are important barriers against VVC, the Lactobacillus metabolite concentration needed to suppress VVC is unknown. Therefore, we quantitatively evaluated Lactobacillus metabolite concentrations to determine their effect on Candida spp., including 27 vaginal strains of Lactobacillus crispatus, Lactobacillus jensenii, Lactobacillus gasseri, Lacticaseibacillus rhamnosus, and Limosilactobacillus vaginalis, with inhibitory abilities against biofilms of Candida clinical isolates. Lactobacillus culture supernatants suppressed viable bacteria by approximately 24%-92% relative to preformed Candida biofilms, but their suppression differed between strains, not species. Lactate production was necessary to suppress preformed biofilms and hyphal elongation of C. albicans, whereas hydrogen peroxide was not always essential. Both lactic acid and hydrogen peroxide were required to suppress Candida planktonic cell growth. Lactobacillus strains that significantly inhibited biofilm formation in culture supernatant also inhibited Candida adhesion to epithelial cells in an actual live bacterial adhesion competition test. Healthy human microflora and their metabolites may play important roles in the development of new antifungal agent against VVC caused by C. albicans.
ARTICLE | doi:10.20944/preprints202010.0162.v1
Subject: Medicine & Pharmacology, Allergology Keywords: biofilm; Candida albicans; E-cadherin; Enterococcus faecalis; FISH; oral mucosa.
Online: 8 October 2020 (08:20:36 CEST)
Candida albicans as an opportunistic pathogen exploits the host immune system and causes a variety of life-threatening infections. The polymorphic nature of this fungus gives it tremendous advantage to breach mucosal barriers and cause a variety of oral and disseminated infections. Enterococcus faecalis, another opportunistic pathogen co-exists with C. albicans in several niches in the human body, including the oral cavity and gastrointestinal tract. However, interactions between E. faecalis and C. albicans on oral mucosal surfaces remain unknown. Here, for the first time, we comprehensively characterized the interactive profiles between laboratory and clinical isolates of C. albicans (SC5314 and BF1) and E. faecalis (OG1RF and 846) on an organotypic oral mucosal model. Our results demonstrated that the two species formed robust biofilms on the mucosal tissue surface with profound surface erosion and fungal invasion. Specifically, this effect was more pronounced in the laboratory isolates than in the clinical isolates. Notably, several genes of C. albicans involved in tissue adhesion, hyphal formation, fungal invasion, and biofilm formation were significantly upregulated in the presence of E. faecalis. This study highlights the strain-dependent cross-kingdom interactions between E. faecalis and C. albicans on oral mucosa, demonstrating the requisite to study more substrate-dependent polymicrobial interactions.
ARTICLE | doi:10.20944/preprints202102.0045.v1
Subject: Biology, Anatomy & Morphology Keywords: Burkina Faso; Candida albicans; ERG11; virulence; susceptibility; Fluconazole; Galleria mellonella
Online: 1 February 2021 (14:31:17 CET)
The aim of this study is to have an idea on the molecular mechanisms of C. albicans resistance to fluconazole in Burkina Faso, by studying the polymorphism of the ERG11 gene, and its implication in the C. albicans virulence and resistance in vivo according to the Galleria mellonella model; (2) Methods: Ten (10) clinical strains including, 5 resistant and 5 susceptible and 1 virulent and susceptible reference strain SC5314 are used. For the estimation of virulence, the larvae were inoculated with 10 μL of C. albicans cell suspension at variable concentrations: 2,5.105, 5.105, 1.106, and 5.106 CFU/larva of each strain. For the in vivo efficacy study, fluconazole was administered at 1, 4 and 16 mg/kg respectively to G. mellonella larvae, after infection by inoculum 5.106 CFU / larvae of each strain; (3) Results: Six (6) non-silent mutations in the ERG11 gene (K143R, F145L, G307S, S405F, G448E, V456I on ERG11p) were found in 4 resistant isolates. Larval mortality depended on fungal burden and strain. The inoculum 5.106 CFU caused 100% mortality in 2 days for the 2 CAAL-1 and CAAL-2 strains carrying the F145L mutation, in 3 days for the reference strain SC5314, in 4 days for the ensemble of resistant strains, and in 5 days for the ensemble of susceptible strains. The comparison of the mortality due to the reference strain SC5314 CFU / larva and the average mortality due to the two mutant F145L strains, shows a significant difference (P <0.05).Fluconazole significantly protected (P> 0.05) the larvae from infection by susceptible strains and the reference strain. However, 100% mortality in 6 days after injection of the resistant strains, was observed (4) Conclusions: Certain mutations in the ERG11 gene such as the F145L mutation are thought to be a source of increased virulence in Candida albicans. Fluconazole effectively protected larvae from infection by susceptible strains in vivo, unlike resistant strain
ARTICLE | doi:10.20944/preprints202101.0437.v1
Subject: Materials Science, Biomaterials Keywords: Candida albicans biofilm; Mixed salivary bacterial biofilm; Phosphated PMMA; Antimicrobials; Salivary pellicle
Online: 22 January 2021 (09:34:24 CET)
Biofilms play a crucial role in the development of Candida-associated denture stomatitis. Inhibition of microbial adhesion to PMMA and phosphate containing PMMA has been examined in this work. C. albicans and mixed salivary microbial biofilms were compared on naked and salivary pre-conditioned PMMA surfaces in the presence or absence of antimicrobials (cetyl pyridinium chloride [CPC], KSL-W, histatin 5 [his 5]). Polymers with varying amounts of phosphate (0-25%) were tested using four C. albicans oral isolates as well as mixed salivary bacteria and 24 h biofilms were assessed for metabolic activity and confirmed using Live/Dead staining and confocal microscopy. Biofilm metabolism was reduced as phosphate density increased (15%: P=0.004; 25%: P=0.001). Loading of CPC on 15% phosphated disks showed a substantial decrease (P=0.001) in biofilm metabolism in the presence or absence of a salivary pellicle. Salivary pellicle on uncharged PMMA enhanced the antimicrobial activity of CPC only. CPC also demonstrated remarkable antimicrobial activity on mixed salivary bacterial biofilms under different conditions displaying the potent efficacy of CPC (350 µg/ml) when combined with an artificial protein pellicle (Biotene half strength).
ARTICLE | doi:10.20944/preprints202105.0752.v1
Subject: Life Sciences, Biochemistry Keywords: Candida albicans; invasive candidiasis; secretome; secreted proteins; hypha; diagnosis; biomarkers; immunoproteomics; SERPA; serologic response.
Online: 31 May 2021 (11:40:35 CEST)
Invasive candidiasis (IC) is associated with high morbidity and mortality in hospitalized patients if not diagnosed early. Long-term use of central venous catheters is a predisposing factor for IC. Hyphal forms of Candida albicans (the major etiological agent of IC) are related to invasion of host tissues. The secreted proteins of hyphae are involved in virulence, host interaction, immune response, and immune evasion. To identify IC diagnostic biomarker candidates, we characterized the C. albicans hyphal secretome by gel-free proteomic analysis, and further assessed the antibody-reactivity patterns to this subproteome in serum pools from 12 patients with non-catheter-associated IC (ncIC), 11 patients with catheter-associated IC (cIC), and 11 non-IC patients. We identified 301 secreted hyphal proteins stratified to stem from the extracellular region, cell wall, cell surface, or intracellular compartments. ncIC and cIC patients had higher antibody levels to the hyphal secretome than non-IC patients. Seven secreted hyphal proteins were identified to be immunogenic (Bgl2, Eno1, Pgk1, Glx3, Sap5, Pra1 and Tdh3). Antibody-reactivity patterns to Bgl2, Eno1, Pgk1 and Glx3 discriminated IC patients from non-IC patients, while those to Sap5, Pra1 and Tdh3 differentiated between cIC and non-IC patients. These proteins may be useful for development of future IC diagnostic tests.
ARTICLE | doi:10.20944/preprints202108.0424.v1
Subject: Chemistry, Medicinal Chemistry Keywords: hydrazone; Candida species; antifungal agents; Candida albicans; Candida glabrata
Online: 23 August 2021 (10:29:47 CEST)
The treatment of benzylidenemalononitriles 3a-c with phenylhydrazines 4a-n in refluxing ethanol did not provide pyrazole derivatives but furnished hydrazones 1a-o. The structure of hydrazones was secured by X-Ray analysis. Newly synthesized hydrazones 1a-o were tested against 8 Candida spp. strains in a dose response assay to determine the minimum inhibitory concentration (MIC99). Five compounds 1c, 1d, 1i, 1k and 1l were identified as promising antifungal agents against Candida spp. (C. albicans SC5314, C. glabrata, C. tropicalis, C. parapsilosis and C. glabrata (R azoles)) with MIC99 values ranging from 16 to 32 µg/mL. To further evaluate the antifungal potential of the active compounds, they have been assayed against a mammalian cell line HEK293 to determine general cell toxicity and on NCI-60 cancer cell lines panel, demonstrating selectivity antifungal activity over cytotoxicity.
BRIEF REPORT | doi:10.20944/preprints202104.0658.v1
Subject: Life Sciences, Biochemistry Keywords: Candida; Candida auris; Culture; Emerging fungus; Isolation; Specific medium
Online: 26 April 2021 (11:06:41 CEST)
Candida auris is an emerging multidrug resistant yeast causing nosocomial infections and associated with high mortality in immunocompromised patients. Rapid identification and characterisation is necessary for its diagnosis and containing spread. In this study, we present a selective culture medium for all C. auris clades. This medium is sensitive with a limit of detection of 102 CFU/ml. The 100% specificity of SCA (Specific C. auris) medium is confirmed on a set of 134 Candida strains, 50 bacterial species and 200 human stool samples. Thus, this medium specifically selects for C. auris isolation from clinical samples, and allows studying its phenotypic profile.
REVIEW | doi:10.20944/preprints202106.0603.v1
Subject: Life Sciences, Biochemistry Keywords: Candida auris; Superbug fungus; biofilm; Candida albicans; nosocomial infection; Candidiasis
Online: 24 June 2021 (11:54:40 CEST)
The newly emerging nosocomial pathogen Candida auris is linked with persistent hospital-acquired infections and abrupt outbreaks across six continents. Genotypic analysis is indicative of the appearance of independent distinct clades of this particular fungus in different geographic locations simultaneously. Intrusive deep seated infections in addition to colonization have been diagnosed primarily in hospitalized patients and have drawn a lot of attention because of different antifungal susceptibility profiles and transmission despite strict preventive measures. Problems with the accurate identification of C. auris using phenotypic and molecular approaches has raised concerns about the detection of relevant levels of the problem. Candida family associated infections are a serious causative agent of mortality and morbidity in immune-compromised individuals. Candida auris are also known as superbug fungus that spreads rapidly all over the world. In 2009, shortly after the first case, various strains across the six continents have been recognized as nosocomial pathogens. Simultaneous and independent C. auris outbreaks appear to be of great concern for the healthcare settings as well as scientific community. Additionally, microbiological misidentification and multidrug resistance, rarely noticed for other non-albicans Candida species, lead to problems in obliteration and frequent treatment failures for C. auris infections. This review article aims to provide a comprehensive and up to date report on the global C. auris outbreaks, considering clinical along with microbiological characteristics, virulence mechanisms and susceptibility to antifungals, as well as the effectiveness of available preventive and therapeutic implementations.
ARTICLE | doi:10.20944/preprints202005.0308.v1
Subject: Medicine & Pharmacology, Pharmacology & Toxicology Keywords: Oral health care products; cyclooxygenase; lipoxygenase; periodontal disease; Candida albicans; Candida glabrata; medicinal herbs
Online: 19 May 2020 (03:45:56 CEST)
Background: Given the increasing request for natural pharmacological molecules, this study assessed the antimicrobial capacity of Pistacia lentiscus L. essential oil (PLL-EO) obtained from the leaves of wild plants growing in North Sardinia (Italy), toward a wide range of periodontal bacteria and Candida including laboratory and clinical isolates sp., together with its anti-inflammatory activity and safety; Methods: PLL-EO was screened by gas chromatography / mass spectrometry. The minimal inhibitory concentration (MIC) was determined. The anti-inflammatory activity was measured by cyclooxygenase (COX 1/2) and lipoxygenase (LOX) inhibition while the antioxidant capacity was determined electro-chemically and by the MTT assay. The WST-1 assay was used to ascertain cytotoxicity toward four line of oral cells; Results: According to the concentrations of terpens, PLL-EO is a pharmacologically active phytocomplex. MICs against periodontal bacteria ranged between 3.13 and 12.5 µg/ml, while against Candida sp. were between 6.25 and 12.5 µg/ml. Oxidation by COX 1/2 and LOX was inhibited by 80% and 20% µg/mL of the oil respectively. Antioxidant activity seemed negligible, and no cytotoxicity arose; Conclusions: PLL-EO exhibits a broad-spectrum activity against periodontal bacteria and Candida, with an interesting dual inhibitory capacity toward COX2 and LOX inflammatory enzymes and without side effects against oral cells.
ARTICLE | doi:10.20944/preprints202012.0182.v1
Subject: Medicine & Pharmacology, Allergology Keywords: candida; bloodstream infection; pediatric; neonatal; antifungal
Online: 8 December 2020 (07:47:24 CET)
Background. Candida bloodstream infections (CBSIs) have decreased among pediatric populations in the United States, but remain an important cause of morbidity and mortality. Species distributions and susceptibility patterns of CBSI isolates diverge widely between children and adults. Awareness of these patterns can inform clinical decision-making for empiric or pre-emptive therapy of children at risk for candidemia. Methods. CBSIs occurring from 2006-2016 among patients in a large children’s hospital were analyzed for age specific trends in incidence rate, risk factors for breakthrough-CBSI and death, as well as underlying conditions. Candida species distributions and susceptibility patterns were evaluated in addition to antifungal agent use. Results. The overall incidence rate of CBSI among this complex patient population was 1.97/1,000 patient-days. About half of CBSI episodes occurred in immunocompetent children and 14% in Neonatal Intensive Care Unit (NICU) patients. Antifungal resistance was minimal: 96.7% of isolates were fluconazole-, 99% were micafungin-, and all were amphotericin susceptible. Liposomal amphotericin was the most commonly prescribed antifungal agent including for NICU patients. Overall CBSI-associated mortality was 13.7%; there were no deaths associated with CBSI among NICU patients after 2011. Conclusions. Pediatric CBSI characteristics differ substantially from those in adults. Improved management of underlying diseases and antimicrobial stewardship may further decrease morbidity and mortality from CBSI while continuing to maintain low resistance rates among Candida isolates.
ARTICLE | doi:10.20944/preprints201805.0122.v1
Subject: Life Sciences, Microbiology Keywords: propolis; Candida spp., biofilm; resistance; synergism
Online: 8 May 2018 (05:58:33 CEST)
The aim of our work was to check if one of the products of natural origin, namely honey bee propolis may be an alternative or supplement to currently used antifungal agents. The activity of 50 ethanolic extracts of propolis (EEPs), harvested in Polish apiaries, was tested on a group of 69 clinical isolates of C. albicans. Most of the EEPs showed satisfactory activity, with minimum fungicidal concentrations (MFC) mainly in the range of 0.08-1.25% (v/v). Eradication of biofilm from polystyrene microtitration plates in 50% (MBEC50) required concentrations in the range of 0.04% (v/v) to more than 1.25% (v/v). High activity was also observed in eradication of biofilm formed by C. glabrata and C. krusei on the surfaces of PVC and silicone catheters. EEPs at subinhibitory concentrations inhibited yeast-to-mycelia morphological transformation of C. albicans in liquid medium and mycelial growth on solid medium. A synergistic effect was observed for the action of EEPs in combination with fluconazole (FLU) and voriconazole (VOR) against C. albicans. In the presence of EEP at concentration as low as 0.02%, the MICs of FLU and VOR were 256 to 32 times lower in comparison to those of the drug alone. Evidences for the fungal cell membrane as the most probable target of EEPs are presented.
ARTICLE | doi:10.20944/preprints202203.0175.v1
Subject: Biology, Other Keywords: Fluconazole; Itraconazole; ROS; mitochondrial activity; Trehalase; Trehalose; Candida parapsilosis
Online: 14 March 2022 (08:36:24 CET)
Central metabolic pathways may play a major role in the virulence of pathogenic fungi. Here, we have investigated the susceptibility of a Candida parapsilosis mutant deficient in trehalase activity (atc1Δ/ntc1Δ strain) to the azolic compounds Fluconazole and Itraconazole. A time-course exposure to Itraconazole but not Fluconazole induced a significant degree of cell-killing in mutant cells compared to the parental strain. Flow cytometry determinations indicated that Itraconazole was able to induce a marked production of endogenous ROS together with a simultaneous increase in membrane potential, these effects being irrelevant after Fluconazole addition. Furthermore, only Itraconazole induced a significant synthesis of endogenous trehalose. The recorded impaired capacity of mutant cells to produce structured biofilms was further increased in the presence of both azoles, with Itraconazole being more effective than Fluconazole. Our results in the opportunistic pathogen yeast C. parapsilosis reinforce the study of trehalose metabolism as an attractive therapeutic target and allow extending the hypothesis that the generation of internal oxidative stress may be a component of the antifungal action exerted by the compounds currently available in medical practice.
REVIEW | doi:10.20944/preprints202106.0575.v1
Subject: Life Sciences, Biochemistry Keywords: Candida glabrata; candidiasis; virulence factors; biofilm; antifungal drug resistance
Online: 23 June 2021 (11:21:53 CEST)
Candida glabrata is a yeast of increasing medical relevance, particularly in critically ill patients. It is the second most isolated Candida species associated with invasive candidiasis (IC) behind C. albicans. The attributed higher incidence is primarily due to an increase in the acquired immunodeficiency syndrome (AIDS) population, cancer, and diabetes patients. The elderly population and the frequent use of indwelling medical devices are also predisposing factors. The work aimed to review various virulence factors that facilitate the survival of pathogenic C. glabrata in IC. The available published research articles related to the pathogenicity of C. glabrata were retrieved and reviewed from four credible databases, mainly Google Scholar, ScienceDirect, PubMed, and Scopus. The articles highlighted many virulence factors associated with pathogenicity in C. glabrata, including adherence to a susceptible host surface, evading host defences, and producing hydrolytic enzymes (e.g., phospholipases, proteases, and haemolysins). The factors facilitate infection initiation. Other virulent factors include iron regulation and genetic mutations. Accordingly, biofilm production, tolerance to high-stress environments, and development of resistance to the antifungal drug, notably to fluconazole and other azole derivatives, were reported. The review provided evident pathogenic mechanisms and antifungal resistance associated with C. glabrata in ensuring its sustenance and survival.
ARTICLE | doi:10.20944/preprints202102.0222.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Prosthodontics; Edentulism; Elderly; Complete Denture; Candida Albicans; Antimicrobial activity
Online: 8 February 2021 (21:38:48 CET)
To assess the clinical efficacy of a novel organic olive oil-based denture adhesive and its effect on Candida Albicans growth in maxillary edentulous individuals wearing complete dentures. Individuals were selected from two Dental Schools in Portugal and Spain. Twenty-eight complete dentures were relined, following a standardized protocol. The novel product (Test) was compared with a commercialized adhesive (Control) and Vaseline (Placebo) randomly assigned in a cross-study design. The retention resistance was measured with a Gnathometer and a dynamometer, the patient related outcome evaluations with a 5-points questionnaire and the Candida albicans growth in a Sabouraud dextrose agar (SDA) medium in order to evaluate differences between the placebo and experimental product. Twenty-three participants were included. Dynamometer evaluation showed significant differences between not using a denture adhesive and using either (experimental, p = .03; control, p = .04), no significant differences between the two adhesives (p > .05). In the subjective analysis, the experimental adhesive showed a significantly longer effectiveness (p = .001); the control reported better results at taste (p = .03) in chewing (p = .001). The test adhesive showed better (p < .001) Candida albicans growth inhibition. The experimental adhesive showed longer effectiveness than the control and placebo with a better inhibition capacity for the growth of Candida albicans, patients reported better abilities for speech, chewing, taste and retirement in the control adhesive.
ARTICLE | doi:10.20944/preprints201909.0148.v1
Subject: Life Sciences, Microbiology Keywords: Candida spp.; PCR-RFLP; Honduras; HardyCHROM®; MicroScan®
Online: 15 September 2019 (03:30:16 CEST)
Candida species are one of the most important causes of human infections, especially in hospitals and among immunocompromised patients. The correct and rapid etiological identification of yeast infections is important to provide adequate therapy, reduce mortality and control outbreaks. In this study, Candida species were identified in patients with suspected fungal infection, and phenotypic and genotypic identification methods were compared. A total of 167 axenic fungal cultures and 46 clinical samples were analyzed by HardyCHROM®, MicroScan®, and PCR-RFLP. The species of the C. albicans complex were the most frequent, followed by C. tropicalis and C. glabrata. Less common but clinically relevant species of Candida were also isolated. The comparison between the three methods was concordant, especially for the most common Candida species. Fungal DNA amplification was successful in all clinical samples.
REVIEW | doi:10.20944/preprints201808.0306.v1
Subject: Biology, Other Keywords: Candida glabrata, drug resistance, tolerance, FKS, MSH2, echinocandin, azole
Online: 17 August 2018 (12:43:43 CEST)
Candida glabrata has thoroughly adapted to successfully colonize human mucosal membranes and survive in vivo pressures prior to and during antifungal treatment. Out of all the medically relevant Candida species, C. glabrata has emerged as a leading cause of azole, echinocandin, and multidrug (MDR: azole + echinocandin) adaptive resistance. Neither mechanism of resistance is intrinsic to C. glabrata, since stable genetic resistance depends on mutation of drug target genes, FKS1 and FKS2 (echinocandin resistance), and a transcription factor, PDR1, which controls expression of major drug transporters, such as CDR1 (azole resistance). However, another hallmark of C. glabrata is the ability to withstand drug pressure both in vitro and in vivo prior to stable ‘genetic escape’. Additionally, these resistance events can arise within individual patients, which underscores the importance of understanding how this fungus is adapting to its environment and to drug exposure in vivo. Here, we explore the evolution of echinocandin resistance as a multistep model that includes general cell stress, drug adaptation (tolerance), and genetic escape. The extensive genetic diversity reported in C. glabrata will be highlighted.
REVIEW | doi:10.20944/preprints202203.0262.v1
Subject: Life Sciences, Microbiology Keywords: Keywords: antifungal; azole; synergy; mycosis; resistance; Candida; dermatophytes; natural products
Online: 18 March 2022 (07:04:16 CET)
Fungal infections impact the lives of at least 12 million people every year, killing over 1.5 million. Wide-spread use of fungicides and prophylactic antifungal therapy have driven resistance in many serious fungal pathogens, and there is an urgent need to expand the current antifungal ar-senal. Recent research has focused on improving azoles, our most successful class of antifungals, by looking for synergistic interactions with secondary compounds. Synergists can co-operate with azoles by targeting steps in related pathways, or they may act on mechanisms related to re-sistance like active efflux or on totally disparate pathways or processes. A variety of sources of potential synergists have been explored, including pre-existing antimicrobials, pharmaceuticals approved for other uses, bioactive natural compounds and phytochemicals, and novel synthetic compounds. Synergy can successfully widen the antifungal spectrum, decrease inhibitory dosag-es, reduce toxicity, and prevent the development of resistance. This review highlights the diversity of mechanisms that have been exploited for the purposes of azole synergy and demonstrates that synergy remains a promising approach for meeting the urgent need for novel antifungal strate-gies.
ARTICLE | doi:10.20944/preprints202103.0147.v1
Subject: Life Sciences, Biochemistry Keywords: Candida sp.; head - neck tumor; innovative antifungals; azole-resistant; Ruta graveolens.
Online: 4 March 2021 (09:18:46 CET)
The problem of drug resistance in terms of antifungal therapy, unknown until a few years ago, is assuming increasing importance. Particularly in immunosuppressed patients and subject to chemotherapy and radiotherapy. In the last years the use of essential oils as approach to improving the effectiveness of antifungal agents and reducing the antibiotic resistant has been proposed. Our research aimed to evaluate the antifungal activity of Colombian essential oil of Ruta graveolens (REO) against clinical strains of Candida albicans, Candida parapsilopsis, C. glabrata and Candida tropicalis. The data obtained showed that Candida tropicalis and Candida albicans were most sensible strains showing minimum inhibitory concentrations (MIC) of 0.5 and 1.0 µg/ml of REO. The Time Kill Kinetics assay demonstrated that REO showed fungicide effect against C. tropicalis and fungistatic effect against C. albicans. In addition, the 40% of the biofilm formed by C. albicans was eradicated using 1% of REO after 1 hour of exposure.
ARTICLE | doi:10.20944/preprints202110.0104.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: Candida; Corneal infection; Corneal ulcer; Contact lens; Fungal infection; Fusarium; Infectious keratitis; Keratoplasty
Online: 6 October 2021 (10:45:42 CEST)
Fungal keratitis (FK) is a serious ocular infection that often poses significant diagnostic and therapeutic dilemmas. This study aimed to examine the causes, clinical characteristics, outcomes, and prognostic factors of FK in the UK. All culture-positive and culture-negative presumed FK (with complete data) that presented to Queen’s Medical Centre, Nottingham, and Queen Victoria Hospital, East Grinstead, between 2011 and 2020 were included. A total of 117 patients (n=117 eyes) with FK were included in this study. The mean age was 59.0±19.6 years (range, 4-92 years) and 51.3% patients were female. Fifty-three fungal isolates were identified from 52 (44.4%) culture-positive cases, with Candida spp. (33, 62.3%), Fusarium spp. (9, 17.0%), and Aspergillus spp. (5, 9.4%) being the most common organisms. Ocular surface disease (60, 51.3%), prior corneal surgery (44, 37.6%), and systemic immunosuppression (42, 35.9%) were the three most common risk factors. Hospitalisation for intensive treatment was required for 95 (81.2%) patients, with a duration of 18.9±16.3 days. Sixty-six (56.4%) patients required additional surgical interventions for eradicating the infection. Emergency therapeutic/tectonic keratoplasty was performed in 29 (24.8%) cases, though 13 (44.8%) of them failed at final follow-up. The final corrected-distance-visual-acuity (CDVA) was 1.67±1.08 logMAR. Multivariable logistic regression analyses demonstrated increased age, large infiltrate size (>3mm), and poor presenting CDVA (<1.0 logMAR) as significant negative predictive factors for poor visual outcome (CDVA of <1.0 logMAR) and poor corneal healing (>60 days of healing time or occurrence of corneal perforation requiring emergency keratoplasty; all p<0.05). In conclusion, FK represents a difficult-to-treat ocular infection that often results in poor visual outcome, with a high need for surgical interventions. Innovative treatment strategies are urgently required to tackle this unmet need.
ARTICLE | doi:10.20944/preprints202109.0117.v1
Subject: Biology, Plant Sciences Keywords: Anticandidosic activity; Candida albicans; Quercus suber L.; Methanolic extracts; Traditional pharmacopoeia; Acute Toxicity
Online: 7 September 2021 (10:32:31 CEST)
The cork oak (Quercus suber L.), endemic essence of the Mediterranean Basin, is commonly used in traditional pharmacopoeia. The main objective of this work is to enhance the valorization of this plant species through the study of the anticandidosic activity of cork oak bark methalonic extracts in order to develop an efficient natural formulation for Candidiasis treatment.The anticandidosic activity of methanolic extracts of Q. suber bark stemming from decoction, maceration and Soxhlet methods of extraction in was tested on five different Candida albicans strains. Our results showed that all the tested extracts displayed an inhibitive activity, which varies according to the obtained extract and the tested strain. The best anticandidosic potential was observed with extracts obtained with Soxhlet method. The study of the acute toxicity showed that the lethal dose is 1150 mg/kg in mice, which remained moderately toxic according to Hodge and Sterner classification scale. Thus, this extract can be used in phytotherapy without danger in doses that are below 300 mg/kg of corporal weight. Based on these results, we can conclude that Cork oak bark extracts can be used to treat Candida albicans infections.
CASE REPORT | doi:10.20944/preprints202008.0198.v1
Subject: Life Sciences, Microbiology Keywords: SARS-CoV-2; coinfection; diabetes, bloodstream infection; Candida glabrata; echinocandin resistance; FKS mutation
Online: 7 August 2020 (12:54:12 CEST)
Coinfections with bacteria or fungi may be a frequent complication of COVID-19, although coinfections with Candida species in COVID-19 patients remain rare. We report the 53-day clinical course of a complicated type-2 diabetes patient diagnosed with COVID-19, who developed bloodstream infections initially due to methicillin-resistant Staphylococcus aureus, secondly to multidrug-resistant Gram-negative bacteria, and lastly to a possibly fatal Candida glabrata. Development of FKS-associated pan-echinocandin resistance in the C. glabrata isolated from the patient after 13 days of caspofungin treatment aggravated the situation. The patient died of septic shock shortly before the prospect of receiving potentially effective antifungal therapy. This case emphasizes the importance of early diagnosis and monitoring for antimicrobial drug-resistant coinfections to reduce their unfavorable outcomes in COVID-19 patients.
ARTICLE | doi:10.20944/preprints201911.0293.v1
Subject: Life Sciences, Microbiology Keywords: Candida spp; cryptic species; Honduras; PCR-RFLP; hwp1 gene; gpi gene; C. auris
Online: 24 November 2019 (16:05:45 CET)
Candida spp. are the most common cause of fungal infections worldwide. The taxonomy of Candida is controversial and has undergone recent changes due to novel genetically related species. Therefore, some complexes of cryptic species have been proposed. In clinical settings, the correct identification of Candida species is relevant since some species are associated with high resistance to antifungal drugs and increased virulence. This study aimed to identify the species of four Candida complexes (C. albicans, C. glabrata, C. parapsilosis, and C. haemulonii) by molecular methods. This is the first report of six cryptic Candida species in Honduras: C. dubliniensis, C. africana, C. duobushaemulonii, C. orthopsilosis, and C. metapsilosis, and it is also the first report of the allele hwp1-2 of C. albicans sensu stricto. It was not possible to demonstrate the existence of C. auris among the isolates of the C. haemulonii complex. We also propose a simple method based on PCR-RFLP for the discrimination of the multi-resistant pathogen C. auris within the C. haemulonii complex.
Subject: Chemistry, Analytical Chemistry Keywords: (S)-Practolol; paracetamol; (S)-pindolol; (S)-carteolol; Candida antarctica Lipase B; chiral chromatography; dimer formation
Online: 4 March 2021 (08:34:02 CET)
The -blocker (S)-practolol ((S)-N-(4-(2-hydroxy (isopropylamino)propoxy)phenyl)acetamide) was synthesized with 96% enantiomeric excess (ee) from the chlorohydrin (R)-N-(4-(3-chloro-2 hydroxypropoxy)phenyl)acetamide, which was produced in 97% ee and with 27% yield. Racemic building block 1-((1H-indol-4-yl)oxy)-3-chloropropan-2-ol for the -blocker pindolol was produced in 53% yield and (R)-1-((1H-indol-4-yl)oxy)-3-chloropropan-2-ol was produced in 92% ee. The chlorohydrin 7-(3-chloro-2-hydroxypropoxy)-3,4-dihydroquinolin-2(1H)-one, a building block for a derivative of carteolol was produced in 77% yield. (R)-7-(3-chloro-2-hydroxypropoxy)-3,4-dihydroquinolin-2(1H)-one was obtained in 96% ee. The S-enantiomer of this carteolol derivative was produced in 97% ee in 87% yield. Racemic building block 5-(3-chloro-2-hydroxypropoxy)- 3,4-dihydroquinolin-2(1H)-one, building block for the drug carteolol was also produced in 53% yield, with 99% ee of the R-chlorohydrin (R)-5-(3-chloro-2-hydroxypropoxy)-3,4-dihydroquinolin-2(1H)-one. The yield of all four chlorohydrins increased by use of catalytic amounts of base. The reason for this was found to be less formation of the dimeric by-products compared to use of higher concentration of the base. An overall reduction of reagents and reaction time was also obtained compared to our previous reported data of similar compounds. The enantiomers of the chlorohydrin building blocks were obtained by kinetic resolution of the racemate in transesterification reactions catalyzed by Candida antarctica Lipase B (CALB) from SyncoZymes Co, Shanghai, China. Optical rotations confirmed the absolute configuration of the enantiopure drugs.
ARTICLE | doi:10.20944/preprints202210.0412.v1
Subject: Life Sciences, Microbiology Keywords: biolog phenotypic technology; Candida; energy-dispersive X-ray spectroscopy; genotype; multilocus DNA sequencing; one new taxon; yeast
Online: 26 October 2022 (10:15:55 CEST)
The majority of Candida species are known as non-pathogenic yeasts and rarely involved in human diseases. However, recently case reports of human infections caused by non-albicans Candida species have increased, mostly in immunocompromised hosts. Our study aimed to describe and caracterise as thoroughly as possible, a new species of the Candida genus, named here Candida massiliensis (PMML0037), isolated from a clinical sample of human sputum. We compared genetic data based on the sequences of four genetic regions: "Internal Transcribed Spacers" of rRNA, D1/D2 domains (28S large subunit rRNA) and part of the genes encoding Translation Elongation Factor 1-α and β-tubulin2, to morphological characters, from scanning electron microscopy (TM 4000 Plus, SU5000), physiological, including the results of oxidation and assimilation tests of different carbon sources by the Biolog system, and chemical mapping by Energy-Dispersive X-ray Spectroscopy. Lastly, the in vitro antifungal susceptibility profile was performed using the E-testTM exponential gradient method. The multilocus analysis supported the genetic position of Candida massiliensis (PMML0037) as a new species of the genus Candida, and the phenotypic analysis highlighted its unique morphological and chemical profile when compared to other Candida species included in the study.
ARTICLE | doi:10.20944/preprints202105.0039.v1
Subject: Chemistry, Analytical Chemistry Keywords: antifungal activity; Candida albicans; antibiofilm effect; mode of action; cytotoxicity; hemolytic assay; HOMO-LUMO; molecular electrostatic potential
Online: 5 May 2021 (12:04:01 CEST)
There is a need to search for new antifungals, especially for the treatment of the invasive Candida infections, caused mainly by C. albicans. These infections are steadily increasing at an alarming rate, mostly among immunocompromised patients. The newly synthesized compounds (3a-3k) were characterized by physico-chemical parameters and investigated for antimicrobial activity using the microdilution broth method to estimate minimal inhibitory concentration (MIC). Additionally, their antibiofilm activity and mode of action together with the effect on the membrane permeability in C. albicans were investigated. Biofilm biomass and its metabolic activity were quantitatively measured using crystal violet (CV) staining and tetrazolium salt (XTT) reduction assay. The cytotoxic effect on normal human lung fibroblasts and hemolytic effect were also evaluated. The results showed differential activity of the compounds against yeasts (MIC = 0.24-500 µg/mL) and bacteria (MIC = 125-1000 µg/mL). Most compounds possessed strong antifungal activity (MIC = 0.24-7.81 µg/mL). The compounds 3b, 3c, and 3e, showed no inhibitory (at 1/2 MIC) and eradication (at 8 x MIC) effect on C. albicans biofilm. Only slight decrease in the biofilm metabolic activity was observed for compound 3b. Moreover, the studied compounds increased the permeability of the membrane/cell wall of C. albicans and their mode of action may be related to action within the fungal cell wall structure and/or within the cell membrane. It is worth noting that the compounds had no cytotoxicity effect on pulmonary fibroblasts and erythrocytes at concentrations showing anticandidal activity. The present studies in vitro confirm that these derivatives appear to be a very promising group of antifungals for further preclinical studies.
ARTICLE | doi:10.20944/preprints202212.0572.v1
Subject: Biology, Other Keywords: formate dehydrogenase; Candida boidinii; protein engineering; X-ray crystallography; structural biology; structural dynamics; Turkish Light Source; Turkish DeLight.
Online: 30 December 2022 (08:03:07 CET)
Candida boidinii NAD+-dependent formate dehydrogenase (CbFDH) has gained significant attention for its potential applications in the production of biofuels and various industrial chemicals from inorganic carbon dioxide. In this study, we present an atomic X-ray crystal structure of the apo CbFDH to 1.4 Å resolution determined at cryogenic temperature at the Turkish Light Source, “Turkish DeLight”. This structure offers a comprehensive view of the apo enzyme's dynamics, filling the gaps in our understanding from previous studies. Also, comparison of our high-resolution apo and previously available holo enzyme structures reveals major conformational changes of this dynamic enzyme in the absence and presence of the coenzyme and substrate/inhibitor complexes. Collectively all these information may provide invaluable insights into future protein engineering efforts that could enhance enzymatic activity and stability, potentially increasing its efficiency and effectiveness of CbFDH in industrial processes.
REVIEW | doi:10.20944/preprints202102.0455.v1
Subject: Medicine & Pharmacology, Allergology Keywords: essential oils; water extracts; ethanol extracts; periodontal bacteria; Candida; natural antimicrobials; natural anti-inflammatory; Sardinian plants; pharmaceutical plants
Online: 22 February 2021 (10:53:13 CET)
There is an increasing interest in revisiting plants for drug discovery proving scientifically their role as remedies. Pistacia lentiscus (PL) is a wild-growing shrub rich in terpenoids, which are pharmacological appealing. The more recurrent components in the oil are represented by α-pinene, terpinene, caryophyllene, limonene, and myrcene. High concentration of polyphenols enriches the extracts. PL-extracts showed in vitro and in animal model strong anti-inflammatory and anti-oxidative activities. The anti-inflammatory activity mainly occurs due to inhibition of NF-kB pathway or directly toward the proinflammatory cytokines, or arachidonic acid cascade against COX-2 and LOX. The antimicrobial activity of PL essential oil and extracts includes among others Staphylococcus aureus, Escherichia coli, periodontal bacteria and Candida sp.. In conclusion, the biological properties, and particularly the anti-inflammatory and anti-microbial capacity, propose PL as a new safe pharmaceutical agent.
ARTICLE | doi:10.20944/preprints202001.0182.v1
Subject: Chemistry, Medicinal Chemistry Keywords: dinoflagellate; Karenia mikimotoi; glycolipids; monogalactosyldiacylglycerol; monogalactosylmonoacylglycerol; polyunsaturated fatty acid methyl ester; Staphylococcus aureus; Escherichia coli; Candida albicans; anti-inflammatory activity
Online: 17 January 2020 (09:18:08 CET)
A New monogalactosyldiacylglycerol (MGDG), a known monogalactosylmonoacylglycerol (MGMG) and a known polyunsaturated fatty acid methyl ester (PUFAME) were isolated from the marine dinoflagellate Karenia mikimotoi. The planar structure of the glycolipids was elucidated using MS and NMR spectroscopic analyses and comparisons to the known glycolipid to confirm its structure. The isolation of PUFAME strongly supports the polyunsaturated fatty acid fragment of these glycolipids. The relative configuration of the sugar was deduced by comparisons of 3JHH values and proton chemical shifts with those of known glycolipids. All isolated compounds MGDG, MGMG and PUFAME (1-3) were evaluated for their antimicrobial and anti-inflammatory activity. All compounds modulated macrophage responses, with compound 3 exhibiting the greatest anti-inflammatory activity.