Immune response and essential oil activity against pathogenic Candida species ,,

The pathogenic fungi Candida albicans and C. glabrata are present on and in bodies of the majority of the healthy population. However, in immunocompromised patients, they can cause life-threatening diseases that are often hard to treat due to resistance. There are several strategies that can be employed to try and overcome this resistance. In the first part of this work, we try and uncover the mechanisms underlying the resistance of C. albicans biofilms against the murine immune system. Knowing the underlying mechanisms will make it possible to overcome resistance. There are three possible hypotheses that might explain this resistance. First, it is possible that the immune system is unaware of biofilm presence. Alternatively, the biofilm might steer the immune response away from an effective one and last the biofilm may be resistant to the efficient immune response that is mounted. By employing a combination of the subcutaneous catheter model system and the systemic infection model in mice, we try to estimate the contribution of each of these three hypotheses. In the second part of this work we research the vapor-phase-mediated antimicrobial activity (VMAA) of essential oils (EOs) and essential oil components (EOCs). Therefore, we first develop an in vitro assay to allow for the detection of the VMAA using standard laboratory equipment. After this, we assess the VMAA of a collection of over 200 essential oils and components against C. albicans and C. glabrata. As such we determine which EO(C)s are most active against these pathogenic fungi and possibly find chemical features within the components that determine their activity.status: publishe

Recent insights into Candida albicans biofilm resistance mechanisms

Like other microorganisms, free-living Candida albicans is mainly present in a three-dimensional multicellular structure, which is called a biofilm, rather than in a planktonic form. Candida albicans biofilms can be isolated from both abiotic and biotic surfaces at various locations within the host. As the number of abiotic implants, mainly bloodstream and urinary catheters, has been increasing, the number of biofilm-associated bloodstream or urogenital tract infections is also strongly increasing resulting in a raise in mortality. Cells within a biofilm structure show a reduced susceptibility to specific commonly used antifungals and, in addition, it has recently been shown that such cells are less sensitive to killing by components of our immune system. In this review, we summarize the most important insights in the mechanisms underlying biofilm-associated antifungal drug resistance and immune evasion strategies, focusing on the most recent advances in this area of research.status: publishe

Comparison between the vapor-phase-mediated anti-Candida activity of conventional and organic essential oils

status: accepte

Comparison between the vapor-phase-mediated anti-Candida activity of conventional and organic essential oils

© 2018, Badebio Biotechnololgy Ltd. All rights reserved. Essential oils (EOs) are known for their antimicrobial activities against a broad range of microorganisms. In this study we investigated if EOs obtained from plants grown by organic farming are more potent than those obtained from conventional farming, or vice versa. Therefore, the aim of this study was to compare pairwise the inhibitory vapor-phase-mediated antimicrobial activity of 33 certified organic EOs and as many equivalent EOs without such certification against two human pathogenic Candida species using the vapor-phase-mediated susceptibility assay. Overall, C. glabrata is more susceptible than C. albicans to EOs, but we could not show a significant difference in EO antimicrobial activity between certified organic and without certification.status: publishe

Introducing a quantitative assay to assess the volatile antimicrobial activities of essential oils and their components

abstract selected (presentation)status: publishe

Identification of multiple interacting alleles conferring low glycerol and high ethanol yield in Saccharomyces cerevisiae ethanolic fermentation

BACKGROUND: Genetic engineering of industrial microorganisms often suffers from undesirable side effects on essential functions. Reverse engineering is an alternative strategy to improve multifactorial traits like low glycerol/high ethanol yield in yeast fermentation. Previous rational engineering of this trait always affected essential functions like growth and stress tolerance. We have screened Saccharomyces cerevisiae biodiversity for specific alleles causing lower glycerol/higher ethanol yield, assuming higher compatibility with normal cellular functionality. Previous work identified ssk1E330N…K356N as causative allele in strain CBS6412, which displayed the lowest glycerol/ethanol ratio. RESULTS: We have now identified a unique segregant, 26B, that shows similar low glycerol/high ethanol production as the superior parent, but lacks the ssk1E330N…K356N allele. Using segregants from the backcross of 26B with the inferior parent strain, we applied pooled-segregant whole-genome sequence analysis and identified three minor quantitative trait loci (QTLs) linked to low glycerol/high ethanol production. Within these QTLs, we identified three novel alleles of known regulatory and structural genes of glycerol metabolism, smp1R110Q,P269Q, hot1P107S,H274Y and gpd1L164P as causative genes. All three genes separately caused a significant drop in the glycerol/ethanol production ratio, while gpd1L164P appeared to be epistatically suppressed by other alleles in the superior parent. The order of potency in reducing the glycerol/ethanol ratio of the three alleles was: gpd1L164P > hot1P107S,H274Y ≥ smp1R110Q,P269Q. CONCLUSIONS: Our results show that natural yeast strains harbor multiple specific alleles of genes controlling essential functions, that are apparently compatible with survival in the natural environment. These newly identified alleles can be used as gene tools for engineering industrial yeast strains with multiple subtle changes, minimizing the risk of negatively affecting other essential functions. The gene tools act at the transcriptional, regulatory or structural gene level, distributing the impact over multiple targets and thus further minimizing possible side-effects. In addition, the results suggest polygenic analysis of complex traits as a promising new avenue to identify novel components involved in cellular functions, including those important in industrial applications.status: publishe

A Framework for Understanding the Evasion of Host Immunity by Candida Biofilms

Candida biofilms are a major cause of nosocomial morbidity and mortality. The mechanism by which Candida biofilms evade the immune system remains unknown. In this perspective, we develop a theoretical framework of the three, not mutually exclusive, models, which could explain biofilm evasion of host immunity. First, biofilms may exhibit properties of immunological silence, preventing immune activation. Second, biofilms may produce immune-deviating factors, converting effective immunity into ineffective immunity. Third, biofilms may resist host immunity, which would otherwise be effective. Using a murine subcutaneous biofilm model, we found that mice infected with biofilms developed sterilizing immunity effective when challenged with yeast form Candida. Despite the induction of effective anti-Candida immunity, no spontaneous clearance of the biofilm was observed. These results support the immune resistance model of biofilm immune evasion and demonstrate an asymmetric relationship between the host and biofilms, with biofilms eliciting effective immune responses yet being resistant to immunological clearance

Assay and recommendations for the detection of vapour-phase-mediated antimicrobial activities of volatiles

Antimicrobial activity assays can be carried out in aqueous solutions using multi-well plates. However, some bioactive compounds are volatile and can cause effects at a distance. To detect such vapour-phase-mediated antimicrobial activity, we introduce the vapour-phase-mediated patch assay, a simple bioassay that uses standard microtitre plates. As a proof-of-principle, we use the vapour-phase-mediated patch assay to test a small but chemically diverse set of selected essential oils with known antifungal activities i.e. Origanum compactum, Artemisia dracunculus, Cinnamomum camphora ct linalool, Cinnamomum cassia and Melissa officinalis, as well as their corresponding major components carvacrol, estragole, linalool, trans-cinnamaldehyde and citral, against two pathogenic Candida species. As all but one of the tested essential oils i.e. Artemisia dracunculus and its corresponding component estragole, showed vapour-phase-mediated antimicrobial activity, we conclude that it is a rather common characteristic of essential oils and their components, that should always be taken into consideration. Additionally, we provide suggestions to prevent false positive results due to possible vapour-phase-mediated antimicrobial activities in bioactivity tests.status: publishe