Quorum sensing in Candida species

Quorum sensing is the ability of micro-organisms to communicate, via signalling molecules, in order to coordinate their behaviour. Farnesol and tyrosol were the first molecules identified as Candida albicans quorum sensing molecules. Nowadays non-Candida albicans Candida species, as Candida dubliniensis, Candida parapsilosis, Candida krusei, Candida glabrata and Candida tropicalis, are emerging as pathogens and the identification of their extracellular molecules as well of their effect is of utmost importance. Farnesol, which was firstly described as having an effect on C. albicans morphology and also on C. dubliniensis, was shown to affect C. krusei, C. glabrata and C. tropicalis growth in suspension, without affecting their morphology. Additionally other alcohols as 1-dodecanol, E-nerolidol, 2-phenylethanol and isoamylalchool, have been identified in C. albicans and C. dubliniensis suspended and sessile supernatants. Interestingly, phenylethanol production increases along time, both for planktonic and biofilm cells and for both species. These alcohols were also found to cause high inhibition of filamentation on those two species. Moreover, those molecules were also shown to be secreted by other Candida species and at physiological levels affected C. parapsilosis and C. tropicalis biofilms

Liposomal and Deoxycholate Amphotericin B Formulations: Effectiveness against Biofilm Infections of Candida spp.

Background: candidiasis is the primary fungal infection encountered in patients undergoing prolonged hospitalization, and the fourth leading cause of nosocomial bloodstream infections. One of the most important Candida spp. virulence factors is the ability to form biofilms, which are extremely refractory to antimicrobial therapy and very difficult to treat with the traditional antifungal therapies. It is known that the prophylaxis or treatment of a systemic candidiasis are recurrently taken without considering the possibility of a Candida spp. biofilm-related infections. Therefore, it is important to assess the effectiveness of the available drugs and which formulations have the best performance in these specific infections. Methods: 24-h-biofilms of four Candida spp. and their response to two amphotericin B (AmB) pharmaceutical formulations (liposomal and deoxycholate) were evaluated. Results: generally, Candida glabrata was the less susceptible yeast species to both AmBs. MBECs revealed that it is therapeutically more appealing to use AmB-L than AmB-Deox for all Candida spp. biofilms, since none of the determined concentrations of AmB-L reached 10% of the maximum daily dose, but both formulations showed a very good capacity in the biomass reduction. Conclusions: the liposomal formulation presents better performance in the eradication of the biofilm cells for all the species in comparison with the deoxycholate formulation.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte and Célia F. Rodrigues’ [SFRH/BD/93078/2013] Ph.D. grant. The authors thank the Project “BioHealth—Biotechnology and Bioengineering approaches to improve health quality”, Ref. NORTE-07-0124-FEDER-000027, co-funded by the Programa Operacional Regional do Norte (ON.2—O Novo Norte), QREN, FEDER.info:eu-repo/semantics/publishedVersio

Portrait of matrix gene expression in Candida glabrata biofilms with stress induced by different drugs

(1) Background: Candida glabrata is one of the most significant Candida species associated with severe cases of candidiasis. Biofilm formation is an important feature, closely associated with antifungal resistance, involving alterations of gene expression or mutations, which can result in the failure of antifungal treatments. Hence, the main goal of this work was to evaluate the role of a set of genes, associated with matrix production, in the resistance of C. glabrata biofilms to antifungal drugs. (2) Methods: the determination of the expression of BGL2, XOG1, FKS1, FKS2, GAS2, KNH1, UGP1, and MNN2 genes in 48-h biofilms cells of three C. glabrata strains was performed through quantitative real-time PCR (RT-qPCR), after contact with Fluconazole (Flu), Amphotericin B (AmB), Caspofungin (Csf), or Micafungin (Mcf). (3) Results: Mcf induced a general overexpression of the selected genes. It was verified that the genes related to the production of -1,3-glucans (BGL2, XOG1, GAS2) had the highest expressions. (4) Conclusion: though -1,6-glucans and mannans are an essential part of the cell and biofilm matrix, C. glabrata biofilm cells seem to contribute more to the replacement of -1,3-glucans. Thus, these biopolymers seem to have a greater impact on the biofilm matrix composition and, consequently, a role in the biofilm resistance to antifungal drugs.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte and Célia F. Rodrigues’ [SFRH/BD/93078/2013] Ph.D. grant. We also would like to acknowledge MSD® and Astellas® for the kind donation of Caspofungin and Micafungin, respectivelyinfo:eu-repo/semantics/publishedVersio

Candida albicans and Candida dubliniensis: comparison of biofilm formation in terms of biomass and activity

Candida albicans and C. dubliniensis are two species responsible for oral candidiasis, especially in immunocompromised patients. Microbial infection is preceded by adherence and biofilm formation. Biofilm formation represents the most common form of C. albicans in the oral cavity and is considered to be one of the most important virulence factors. In this study, the biofilm formation ability of C. dubliniensis was compared with that of C. albicans in terms of biomass (quantified using crystal violet) and activity (assessed by formazan salts formation). Both species formed heterogeneous biofilms; however, species and strain variations were seen in the quantification of biomass and activity. There was no correlation between pseudohyphae formation and biofilm formation capability.Fundação para a Ciência e a Tecnologia (FCT) - grant BD3195/2000, project POCTI/BIO/42638/2001

The influence of subinhibitory concentrations of fluconazol and amphotericin B in the adhesion of different Candida species to acrylic

The most common antifungal agents used to treat candidiasis are fluconazol and amphotericinB. Candidal species adhesion is the first step in oral pathogenesis, therefore it is very important to study the behaviour of the adhesion of yeasts submitted to subinhibitory concentrations of antifungal agents. In this study the adhesion was done with Candida albicans and Candida dubliniensis. In order to mimetize real conditions the adhesion assays were performed using a medium with artificial saliva and acrylic as substratum, which is the material used to produce prosthetic devices. The results showed that in the case of Candida albicans the adherence decreased in the presence of fluconazol (1/4MIC=0,25μg/ml). Considering Candida dubliniensis there were no significative differences in the number of adhered cells to acrylic either in the presence of fluconazol or amphotericinB (1/4MIC=0,01μg/ml). Observing cell morphology after adhesion, by SEM, it was possible to notice that cells incubated with subMIC fluconazol formed less hifas than those grown in the presence of subMIC amphotericinB, which can explain the differences in adhesion

Mini-review: antimicrobial central venous catheters : recent advances and strategies

Central venous catheters (CVCs) nowadays constitute critical devices used in medical care, namely in intensive care units. However, CVCs also represent one of the indwelling medical devices with enhanced risk of nosocomial device-related infection. Catheter-related infections (CRIs) are a major cause of patient morbidity and mortality, often justifying premature catheter removal and an increase in costs and use of resources. Adhesion and subsequent biofilm formation on the surfaces of indwelling catheters is elemental to the onset of pathogenesis. Seeking the prevention of CVC colonisation and CRI, a variety of approaches have been studied, tested and, in some cases, already applied in clinical practice. This review looks at the current preventive strategies often used to decrease the risk of CRIs due to colonization and biofilm formation on catheter surfaces, as well as at the more recent approaches under investigation.Fundação para a Ciência e a Tecnologia(SFRH/BPD/47693/2008

The involvement of physico-chemical interactions in the adhesion of Candida albicans and Candida dubliniensis to epithelial cells

Candida albicans and Candida dubliniensis are two pathogenic yeasts particularly hazardous to immunocompromised patients. Adhesion of yeast cells to epithelium is considered one of the virulence factors and its study is of major importance. The main aim of this study was the comparison of the influence of physico-chemical properties on the adhesion of C. albicans and C. dubliniensis to epithelium. Two strains of each Candida species were used in the adhesion assays to HeLa cells. Adhered cells were enumerated by direct microscopic images observation. Yeast cell surface tension parameters and degree of hydrophobicity were determined by contact angle measurement. Pseudohyphae and hyphae formation was analysed by scanning electron microscopy. Yeast cells presented no statistical differences concerning their physico-chemical surface properties. However, the extent of adhesion to epithelium was different among the four strains. As general conclusion, yeast adhesion to epithelium seems to be strain-dependent and not directly correlated with pseudohyphae formation.Fundação para a Ciência e a Tecnologia (FCT); Department of Biology, University of Minho; Instituto de Ciêncicas Biomédicas Abel Salazar, University of Porto; Faculty of Pharmacy, University of Lisbon, Portugal

Candida species adhesion to oral epithelium : factors involved and experimental methodology used

Due to the increasing prevalence and emergence of Non-Candida albicans Candida (NCAC) species, especially in immunosupressed patients, it is becoming urgent to deepen the current knowledge about virulence factors of these species. Adhesion of cells to epithelium is considered one of the major virulence factors of Candida species. However, relatively little is known concerning the adhesion mechanisms of NCAC species to epithelium, as well as about the factors affecting the adhesion process. This review focuses both the mechanisms that regulate the adhesion interactions and the factors involved and the description of the experimental methodology that has been used to perform the adhesion assays.Fundação para a Ciência e a Tecnologia (FCT