Mechanisms of Candida glabrata biofilms tolerance to antifungal agents

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In vitro anti-Candida activity of Glycyrrhiza glabra L.

Publication . Martins, Natália; Ferreira, Isabel C.F.R.; Henriques, Mariana; Silva, Sónia

The severity and frequency of opportunistic fungal infections still growing, concomitantly to the increasing rates of antimicrobial drug’s resistance. Natural matrices have been used over years due to its multitude of health benefits, including antifungal potential. Thus, the present work aims to evaluate the anti-Candida potential of the phenolic extract and individual phenolic compounds of Glycyrrhiza glabra L. (licorice), by disc diffusion assay, followed by determination of the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) for both planktonic cells and biofilms. Licorice extract evidenced inhibitory potential against the nineteen tested Candida strains, but no pronounced effect was observed by testing the most abundant individual phenolic compounds. Candida tropicalis strains were the most sensible, followed by Candida glabrata, Candida parapsilosis and, then, Candida albicans. Lower MIC and MFC values were achieved to C. glabrata and C. tropicalis, which confirms its susceptibility to licorice extract; however, for C. tropicalis strains a higher variability was observed. Anti-biofilm potential was also achieved, being most evident in some C. glabrata and C. tropicalis strains. In general, a twice concentration of the MIC was necessary for planktonic cells to obtain a similar potential to that one observed for biofilms. Thus, an upcoming approach for new antifungal agents, more effective and safer than the current ones, is stablished; notwithstanding, further studies are necessary in order to understand its mechanism of action, as also to assess kinetic parameters.

2016Journal article

Open access

Activity of phenolic compounds from plant origin against Candida species

Publication . Martins, Natália; Barros, Lillian; Henriques, Mariana; Silva, Sónia; Ferreira, Isabel C.F.R.

Candida albicans and other Candida species have been highly associated with several opportunistic fungal infections. Their ability to develop host infections is incited by different determinants, being virulence factors the most highlighted. Molecular targets of the antifungal drugs are crucial components for determination of yeast survival. Ergosterol, nucleic acids and glucan are the most studied molecular targets to destroy Candida species, being considered the basis of the development of new antifungal drugs. However, increasing levels of resistant Candida species to the current antifungal drugs have been observed, making ineffective those agents. Thus, other therapies more effective and safer than the current ones, are being studied, namely the use plant of extracts enriched in phenolic compounds. In this sense, this manuscript provide an historical perspective of the opportunistic fungal infections, molecular targets of the current anti-Candida drugs, as well as a general description of the active principles present in plants, focused on the antifungal potential of whole plant extracts and isolated phenolic compounds, against Candida species.

2015Journal article

Open access

In vivo anti-Candida activity of phenolic extracts and compounds: future perspectives focusing on effective clinical interventions

Publication . Martins, Natália; Barros, Lillian; Henriques, Mariana; Silva, Sónia; Ferreira, Isabel C.F.R.

Candida species have increasingly deserved a special attention among the medical community. In spite of the presence of Candida species as a human commensal, alarming rates of local and systemic infections have been observed, varying from moderate to severe impact. Currently available antifungal drugs have progressively lost their effectiveness, pointing urgently the problem of the microorganisms with acquired-resistance. Natural matrices are secularly used for numerous purposes, being inclusive and highly effective as antimicrobials. Increasing evidence gives a particular emphasis to the contribution of phenolic extracts and related individual compounds. In vitro studies clearly confirm their prominent effects, but the confirmation through in vivo studies, including the involved mechanisms of action, is not so much deepened. Therefore, the present report aims to provide extensive knowledge about all these aspects, highlighting the most efficient phytochemical formulations, including therapeutic doses. Further studies need to be incited to deepen knowledge on this area, namely, focused on clinical trials to provide safer and more effective antimicrobials than the current ones.

2015Journal article

Open access

Plants used in folk medicine: the potential of their hydromethanolic extracts against Candida species

Publication . Martins, Natália; Ferreira, Isabel C.F.R.; Barros, Lillian; Carvalho, Ana Maria; Henriques, Mariana; Silva, Sónia

Currently, opportunistic fungal infections are considered a serious problem regarding public health. Despite the advances towards the synthesis of new antifungal agents, an increasing incidence of drug-resistant microorganisms has been observed. In this sense, other alternatives are necessary. In the present work, the antifungal activity of extracts from ten different plants, commonly used in folk medicine, were evaluated against nineteen Candida strains, including C. albicans, C. glabrata, C. parapsilosis and C. tropicalis species. Although the majority of the extracts had no antimicrobial effect, Juglans regia extract was very effective, exerting an inhibitory effect against all the tested Candida strains, while Eucalyptus globulus was effective against seventeen of them. Pterospartum tridentatum and Rubus ulmifolius presented similar antifungal effects, being effective against six Candida strains. The diameter of halo ranged, respectively, between 9-14 mm and 9-21 mm to the mentioned plant extracts, and the MIC50 values evidenced mainly a fungistatic activity. Both extracts showed similar MIC50 values for C. albicans strains, while C. parapsilosis and C. glabrata were more sensible to E. globulus. Otherwise, all the C. tropicalis strains were more sensible to J. regia. Overall, hydromethanolic plant extracts could constitute promissory alternatives to the traditional antifungal agents.

2015Journal article

Open access