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Validation des activités antiparasitaires des constituants de Muntafara sessilifolia (Apocynaceae)

Muntafara sessilifolia (Baker) Pichon, traditionnellement utilisée à Madagascar lors de fièvres, a été sélectionnée par criblage basé sur l activité antiplasmodiale des extraits. L extraction sélective acide/base avec gradient de pH effectuée sur l extrait MeOH de la poudre d écorce a fournit un extrait alcaloïdique brut et un extrait AcOEt actifs in vitro sur P. falciparum. Leur fractionnement bioguidé a permis d isoler 29 composés : des alcaloïdes mono et bisindoliques et des terpénoïdes dont 11 nouveaux composés. Leurs activités antiparasitaires sur Plasmodium falciparum, Trypanosoma brucei brucei et Leishmania donovani, antibactériennes et cytotoxiques ont été évaluées. Des tests complémentaires ont été effectués afin de connaitre l influence des composants plasmatiques sur leur activité antiplasmodiale, le comportement de ces produits sur des souches de Plasmodium de sensibilité différente et sur le développement des stades précoces du parasite.Muntafara sessilifolia (Baker) Pichon traditionally used for the treatment of fevers in Madagascar, was selected by screening based on the antiplasmodial activity of the extracts. Selective acid-base extraction with gradient of pH performed on MeOH extract from the powdered stem-bark, yielded a crude alkaloid and EtOAc extracts, active in vitro against P. falciparum. Their bioassayguided fractionation led to isolation of 29 compounds : monomeric indole and bisindole alkaloids and terpenoïds, 11 compounds being new. The antiparasitic activities against Plasmodium falciparum, Trypanosoma brucei brucei and Leishmania donovani, were evaluated along with antibacterial and cytotoxic activities on all isolated molecules. Additional tests were conducted to know the influence of plasma components on their antiplasmodial activity, the behavior of the products against strains of P. falciparum of different sensitivity and the development of the early stage of the parasite.PARIS-Museum Hist.Naturelle (751052304) / SudocSudocFranceF

Antifungal and Anti-Biofilm Activities of Acetone Lichen Extracts against Candida albicans

Candida albicans is a commensal coloniser of the human gastrointestinal tract and an opportunistic pathogen, especially thanks to its capacity to form biofilms. This lifestyle is frequently involved in infections and increases the yeast resistance to antimicrobials and immune defenses. In this context, 38 lichen acetone extracts have been prepared and evaluated for their activity against C. albicans planktonic and sessile cells. Minimum inhibitory concentrations of extracts (MICs) were determined using the broth microdilution method. Anti-biofilm activity was evaluated using tetrazolium salt (XTT) assay as the ability to inhibit the maturation phase (anti-maturation) or to eradicate a preformed 24 h old biofilm (anti-biofilm). While none of the extracts were active against planktonic cells, biofilm maturation was limited by 11 of the tested extracts. Seven extracts displayed both anti-maturation and anti-biofilm activities (half maximal inhibitory concentrations IC50_mat and IC50_biof ≤ 100 µg/mL); Evernia prunastri and Ramalina fastigiata were the most promising lichens (IC50_mat < 4 µg/mL and IC50_biof < 10 µg/mL). Chemical profiles of the active extracts performed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) have been analyzed. Depsides, which were present in large amounts in the most active extracts, could be involved in anti-biofilm activities. This work confirmed that lichens represent a reservoir of compounds with anti-biofilm potential

Fungal communities associated with Evernia prunastri , Ramalina fastigiata and Pleurosticta acetabulum : Three epiphytic lichens potentially active against Candida biofilms

International audienceFungal communities associated to three epiphytic lichens active against Candida, were investigated using culture-based methods We hypothetized that associated fungi would contribute to lichens activities. The ability of specific fungi to grow inside or outside lichens was investigated. To detect biogenesis pathways involved in the production of secondary metabolites, genes coding for nonribosomal peptide synthetase (NRPS) and polyketide synthase I (PKS I) were screened by PCR from fungal DNA extracts. Both endo and epilichenic communities were isolated from two fructicose (Evernia prunastri and Ramalina fastigiata) and one foliose (Pleurosticta acetabulum) lichens. A total of 86 endolichenic and 114 epilichenic isolates were obtained, corresponding to 18 and 24 phylogenetic groups respectively suggesting a wide diversity of fungi. The communities and the species richness were distinct between the three lichens which hosted potentially new fungal species. Additionally, the endo- and epilichenic communities differed in their composition: Sordariomycetes were particularly abundant among endolichenic fungi and Dothideomycetes among epilichenic fungi. Only a few fungi colonized both habitats, such as S. fimicola, Cladosporium sp1 and Botrytis cinerea. Interestingly, Nemania serpens (with several genotypes) was the most abundant endolichenic fungus (53% of isolates) and was shared by the three lichens. Finally, 12 out of 36 phylogenetic groups revealed the presence of genes coding for nonribosomal peptide synthetase (NRPs) and polyketide synthase I (PKS I). This study shows that common lichens are reservoirs of diverse fungal communities, which could potentially contribute to global activity of the lichen and, therefore, deserve to be isolated for further chemical studies

Do raspberry extracts and fractions have antifungal or anti-adherent potential against Candida spp.?

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Efficacy of dental unit waterlines disinfectants on a polymicrobial biofilm.

International audienceDue to their high surface-volume ratio, their laminar flow and frequent stagnation periods, dental unit waterlines (DUWL) foster the attachment of microorganisms and the development of biofilm, resulting in the continuous contamination of the outlet water from dental units; this contamination may be responsible for a potential risk of infection due to the exposure of patients and medical staff to droplet inhalation or splashed water. In this study, the anti-biofilm activity of three disinfectants recommended by dental unit manufacturers -Calbenium(©), Oxygenal 6(©) and Sterispray(©) - was evaluated. A dynamic model simulating DUWL conditions was developed and polymicrobial biofilms containing bacteria (Pseudomonas aeruginosa), fungi (Candida albicans) and Free Living Amoeba (FLA: Vermamoeba vermiformis) were allowed to form. The ability of disinfectants to reduce biofilm formation or to eradicate an already formed biofilm was evaluated. Results showed the various effects of the tested disinfectants according to their composition, concentration and the targeted species. V. vermiformis was resistant to disinfectants, regardless of the tested concentrations and the concentrations recommended by manufacturers were not the most appropriate. Results also showed that Calbenium(©) was the most effective disinfectant to reduce already formed biofilms; its maximum efficiency was observed from 0.5% on both P. aeruginosa and C. albicans compared to 2 and 3% respectively for Sterispray(©). The maximum efficiency of Oxygenal(©) was observed from 3% on P. aeruginosa but Oxygenal(©) was unable to totally eliminate C. albicans in the tested conditions, contrary to other disinfectants. Calbenium(©) was able to prevent biofilm formation efficiently even if it displayed no prophylactic activity against V. vermiformis. Overall, the FLA survival may contribute to maintaining other species. Finally the tested disinfectants were partially active against sessile microorganisms and more suitable concentrations could be used to increase their efficacy. Their use in a prophylactic rather than curative way should be recommended

Impact of selection, genetic drift and viral accumulation on the evolution of a plant RNA virus

Genetic control is an efficient way to fight against crop disease, but this method is limited by the pathogen ability to evolve and break the resistance down. In the pepper-Potato virus Y (PVY) pathosystem, studies have demonstrated that the plant genetic background can increase the durability of the major resistance gene (Palloix et al., 2009), especially by constraining pathogen evolution (Quenouille et al., 2013). We conducted an experimental evolution to (i) measure the pathogen ability to adapt to plants combining major resistance gene and partially resistant genetic background and (ii) identify the role of the evolutionary forces induced by the genetic background on virus evolution

Candida albicans enhances initial biofilm growth of Cutibacterium acnes under aerobic conditions

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Access to Anti-Biofilm Compounds from Endolichenic Fungi Using a Bioguided Networking Screening

International audienceEndolichenic microorganisms represent a new source of bioactive natural compounds. Lichens, resulting from a symbiotic association between algae or cyanobacteria and fungi, constitute an original ecological niche for these microorganisms. Endolichenic fungi inhabiting inside the lichen thallus have been isolated and characterized. By cultivation on three different culture media, endolichenic fungi gave rise to a wide diversity of bioactive metabolites. A total of 38 extracts were screened for their anti-maturation effect on Candida albicans biofilms. The 10 most active ones, inducing at least 50% inhibition, were tested against 24 h preformed biofilms of C. albicans, using a reference strain and clinical isolates. The global molecular network was associated to bioactivity data in order to identify and priorize active natural product families. The MS-targeted isolation led to the identification of new oxygenated fatty acid in Preussia persica endowed with an interesting anti-biofilm activity against C. albicans yeasts