Activité anti-biofilm des métabolites secondaires de lichen

The oral bacteria do not only infect the mouth and reside there, but also travel via the blood and reach distant body organs. If left untreated, the dental biofilm that can cause destructive inflammation in the oral cavity may result in serious systemic medical complications. In dental biofilm, Streptococcus gordonii, a primary oral colonizer, constitutes the platform on which late pathogenic colonizers like Porphyromonas gingivalis, the causative agent of periodontal diseases, will bind. The aim of the first study was to determine the antibacterial activity of eleven natural lichen compounds belonging to different chemical families to uncover new antibiotics which can fight against the oral bacteria. Three compounds were shown to have promising antibacterial activities where psoromic acid had the lowest MICs of 11.72 and 5.86 µg/mL against S. gordonii and P. gingivalis, respectively. Novel butyrolactone analogues were then designed and synthesized based on the known lichen antibacterial compounds, lichesterinic acids (B-10 and B-11), by substituting different functional groups on the butyrolactone ring trying to enhance its activity on S. gordonii and P. gingivalis.. Among the derivatives, B-12 and B-13 had the lowest MIC of 9.38 µg/mL where they have shown to be stronger bactericidals, by 2-3 times, than the reference antibiotic, doxycycline. B-12 and B-13 were also the most efficient on P. gingivalis exhibiting MIC of 0.037 and 0.293 µg/mL and MBC of 1.17 and 0.586 µg/mL, respectively. These 2 compounds were then checked for their cytotoxicity against human gingival epithelial cells and macrophages by MTT and LDH assays which confirmed their safety against the tested cell lines. A preliminary study of the structure-activity relationships unveiled the important dual role contributed by two substituents, alkyl chain at C4 and carboxyl group at C5 positions, in their mechanism of action. This was followed by the investigation of B-12 and B-13 for their antibiofilm activity against both oral strains using crystal violet assay and confocal microscopy. Both derivatives displayed a lowest concentration with maximal biofilm inhibition, LCMI, of 9.38 µg/mL against S. gordonii and 1.17 µg/mL against P. gingivalis. However, when sub-inhibitory concentrations of B-12 and B-13 were used, we demonstrated that the two investigated strains were able to form biofilms in vitro. Indeed, this antibiofilm activity decreased as indicated by the expression of the genes implicated in adhesion and biofilm formation. To better understand the mechanism of action of butyrolactones, we have investigated B-13 bacterial localization by synthesizing a fluorescently labeled B-13 with NBD (4-nitro-benzo[1,2,5]oxadiazole) conserving its antibacterial activity. By confocal microscope, we showed that this compound binds to S. gordonii cell surface and this was also demonstrated by HPLC analysis. By adhering to cell surface, B-13 induced cell wall disruption leading to the release of bacterial constituents and consequently, the death of S. gordonii, a Gram-positive bacterium. The expression of two genes, murA and alr, implicated in cell wall synthesis, was modified in the presence of this butyrolactone. Gram-negative bacteria such as P. gingivalis showed also cracked and ruptured cells in the presence of B-13, suggesting that this butyrolactone acts on Gram-positive and Gram-negative strains, but with greater efficacy against the Gram-negatives. Besides, we also demonstrated that the analogue of B-13, B-12, has also induced disruption of P. gingivalis and S. gordonii. All these studies demonstrated that butyrolactones derived from a lichen metabolite can be proposed as potent antibacterial agents against oral pathogens causing serious medical complications.Les bactéries buccales n'infectent pas seulement la bouche mais y resident. Elles peuvent également passer dans la voie sanguine et atteindre des organes secondaires. S’il n'est pas traité, le biofilm dentaire peut provoquer une inflammation destructrice dans la cavité buccale, entrainant de graves complications médicales. Dans ce biofilm, Streptococcus gordonii, colonisateur oral primaire, constitue la plate-forme sur laquelle des colonisateurs pathogènes tardifs comme Porphyromonas gingivalis, l'agent causal des maladies parodontales, se lieront. L'objectif de la première partie de la thèse était de déterminer l'activité antibactérienne de onze composés de lichens appartenant à différentes familles chimiques, pour découvrir de nouveaux antibiotiques pouvant combattre ces bactéries buccales. Nous avons montré que trois composés avaient des activités antibactériennes prometteuses. L'acide psoromique enregistrait les CMIs le plus faibles. De nouveaux analogues de butyrolactone ont ensuite été conçus et synthétisés sur la base des composés antibactériens licheniques connus, les acides lichesteriniques, en substituant différents groupes fonctionnels sur le cycle butyrolactone pour améliorer son activité sur S. gordonii et P. gingivalis. Parmi les dérivés, B-12 et B-13 avaient la plus faible CMI où ils se sont révélés être des bactéricides plus forts, 2 à 3 fois plus, que l'antibiotique, doxycycline. B-12 et B-13 étaient également les plus efficaces vis-à-vis de P. gingivalis. La cytotoxicité de ces 2 composés a ensuite été vérifiée contre les cellulaires épithéliales gingivales humaines et les macrophages. Ils ne présentaient pas de toxicité contre les cellules testées. Une étude préliminaire de relation structure-activité a révélé le double rôle important apporté par deux substituants, chaîne alkyle en C5 et groupe carboxyle en C4 positions, dans leur mécanisme d'action. Ceci a été suivi par l'étude de l’activité antibiofilmique de B-12 et B-13 contre les deux souches orales en utilisant un test de cristal violet et microscopie confocale. Les deux dérivés ont montré, à une concentration plus faible, une inhibition maximale de la formation du biofilm, LCMI, de 9.38 μg/mL contre S. gordonii et 1.17 μg/mL contre P. gingivalis. Cependant, lorsque des concentrations sous-inhibitrices de B-12 et B-13 ont été utilisées, nous avons démontré que les deux souches étudiées pouvaient former des biofilms in vitro, accompagné d’une diminution de l'expression des gènes impliqués dans l'adhésion et la formation de biofilm. Pour mieux comprendre les mécanismes d'action des butyrolactones, nous avons étudié la localisation bactérienne du composé B-13 en synthétisant un B-13 marqué au NBD (4-nitro-benzo [1,2,5] oxadiazole) fluorescent conservant son activité antibactérienne. Par microscopie confocale et HPLC, nous avons montré que ce composé se lie à la surface cellulaire de S. gordonii. Ensuite, B-13 induit une rupture de la paroi cellulaire conduisant à la libération des constituants bactériens et par conséquent, à la mort de S. gordonii, une bactérie Gram-positive. L'expression de deux gènes, murA et alr, impliqués dans la synthèse de la paroi cellulaire, a été modifiée en présence de cette butyrolactone. Les bactéries Gram négatives telles que P. gingivalis ont également montré des cellules abimées présentant une rupture de la paroi en présence de B-13, ce qui suggère que cette butyrolactone agit sur des Gram-positives et Gram-négatives avec une plus grande efficacité contre les Gram-négatives. En outre, nous avons également démontré que l'analogue de B-13, B-12, induit une perturbation de la morphologie de P. gingivalis et S. gordonii. Toutes ces études ont démontré que les butyrolactones dérivées de lichen peuvent être proposés comme des composés antibactériens puissants contre les agents pathogènes oraux qui causent des complications médicales graves

Antibacterial and antibiofilm activities of Scorzonera mackmeliana

International audienceScorzonera have been confiuned to have potent bioactivity. Scorzonera mackmeliana (Asteraceae), the endemic plant to Lebanon, has not yet been investigated. In the present study, we assessed the antibacterial activity of S. mackmeliana extracts against referenced bacterial strains. Extracts from different parts of the plant were evaluated against Staphylococcus, Enterococcus, Escherichia and Pseudomonas species. Phytochemical screening was done by standard biochemical tests and minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and minimal biofilm eradication concentration (MBEC) were detelinined by micro dilution method. The extracts possessed mainly alkaloids, phenols, flavonoids and coumarins. Gram-negative bacteria were most sensitive, whose MICs ranged between 48.98 and 341.85 mg/ml. Water stems extract, rich in phenols, was the most active with an MIC of 48.98 mg/ml. MBC was only recorded for water flowers extract, rich in resins, against P. aeruginosa and ethanolic roots extract, rich in terpenoids, against S. epidermidis with values of 160.85 mg/ml and 284.35 mg/ml, respectively. Furtheimore, antibiofilm activity showed that the lowest MBEC was 0.1 mg/ml for water stems extract with an eradication ability of 91% (p <0.0001). Hence, this study suggests S. mackmeliana as a promising candidate for future investigations to elucidate the major bioactive compound behind the antibacterial and antibiofilm effect

Screening for antibacterial and antibiofilm activities in Astragalus angulosus.

AimIn a search for finding novel therapeutic agents, extracts from an endemic Lebanese plant, Astragalus angulosus, were evaluated for their potential in-vitro antibacterial and antibiofilm activities against three Gram-positive bacterial strains; Staphylococcus epidermidis (CIP444), Staphylococcus aureus (ATCC25923), and Enterococcus faecalis (ATCC29212); in addition to two Gram-negative strains, Escherichia coli (ATCC35218) and Pseudomonas aeruginosa (ATCC27853).Materials and methodsThe plant was collected in April of 2013 and divided into several different portions, then its extracts were obtained by maceration using two different solvents. Extract analysis followed directly where microtiter broth dilution method was employed to assess antibacterial activity, while antibiofilm potential was tested using colorimetric method.ResultsWhole plant ethanolic extract showed the highest bacteriostatic effect at a concentration of 12.78 mg/ml and also was the most versatile exerting its effect against 3 different strains. Other extracts also exhibited an effect but at higher concentrations and each against a single strain. Regarding antibiofilm activity, the majority of the extracts were able to eradicate &gt;50% of S. epidermidis preformed biofilm, where the highest activity was obtained with flower fraction extracted in water, achieving 67.7% biofilm eradication at 0.2 mg/ml.ConclusionsThis plant possesses a promising potential in regard to eradicating bacteria and their biofilms and it is the first contributing step of establishing a library for the endemic Lebanese plants in this domain

Screening for antibacterial and antibiofilm activities in Astragalus angulosus

Aim: in a search for finding novel therapeutic agents, extracts from an endemic Lebanese plant, Astragalus angulosus, were evaluated for their potential in-vitro antibacterial and antibiofilm activities against three Gram positive bacterial strains; Staphylococcus epidermidis (CIP444), Staphylococcus aureus (ATCC25923) and Enterococcus faecalis (ATCC29212);.in addition to two Gram negative strains, Escherichia coli (ATCC35218) and Pseudomonas aeruginosa (ATCC27853). Methods: the plant was collected in April of 2013 and it was divided into several different portions, then its extracts were obtained by maceration using two different solvents. Extract analysis followed directly, where microtiter broth dilution method was employed to assess antibacterial activity, while antibiofilm potential was tested using colorimetric method. Results: whole plant ethanolic extract showed the highest bacteriostatic effect at a concentration of 12.78 mg ml-1 and also was the most versatile exerting its effect against 3 different strains. Other extracts also exhibited an effect but at higher concentrations and each against a single strain. Regarding antibiofilm activity, the majority of the extracts were able to eradicate &gt;50% of Staphylococcus epidermidis preformed biofilm, where the highest activity was obtained with flower fraction extracted in water, achieving 67.7% biofilm eradication at 0.2 mg ml-1. Conclusions: This plant possesses a promising potential in regard to eradicating bacteria and their biofilms, and it is the first contributing step of establishing a library for the endemic Lebanese plants in this domain. [J Complement Med Res 2017; 6(1.000): 50-57

Next-Generation Probiotics and Their Metabolites in COVID-19

International audienceSince December 2019, a global pandemic has been observed, caused by the emergence of a new coronavirus, SARS CoV-2. The latter is responsible for the respiratory disease, COVID-19. The infection is also characterized by renal, hepatic, and gastrointestinal dysfunctions suggesting the spread of the virus to other organs. A dysregulated immune response was also reported. To date, there is no measure to treat or prevent SARS CoV-2 infection. Additionally, as gut microbiota composition is altered in patients with COVID-19, alternative therapies using probiotics can be considered to fight SARS CoV-2 infection. This review aims at summarizing the current knowledge about next-generation probiotics (NGPs) and their benefits in viral respiratory tract infections and in COVID-19. We describe these bacteria, highlighted by studies using metagenomic approaches. In addition, these bacteria generate metabolites such as butyrate, desaminotyrosine, and secondary bile acid, suggested to prevent viral respiratory infections. Gut microbial metabolites transported via the circulation to the lungs could inhibit viral replication or improve the immune response against viruses. The use of probiotics and/or their metabolites may target either the virus itself and/or the immunologic process. However, this review showed that more studies are needed to determine the benefits of probiotics and metabolite products in COVID-19

SARS-CoV-2 and Prevotella spp.: friend or foe? A systematic literature review

International audienceDuring this global pandemic of the COVID- 19 disease, a lot of information has arisen in the media and online without scientific validation, and among these is the possibility that this disease could be aggravated by a secondary bacterial infection such as Prevotella, as well as the interest or not in using azithromycin, a potentially active antimicrobial agent. The aim of this study was to carry out a systematic literature review, to prove or disprove these allegations by scientific arguments. The search included Medline, PubMed, and Pubtator Central databases for English- language articles published 1999???2021. After removing duplicates, a total of final eligible studies (n=149) were selected. There were more articles showing an increase of Prevotella abundance in the presence of viral infection like that related to Human Immunodeficiency Virus (HIV), Papillomavirus (HPV), Herpesviridae and respiratory virus, highlighting differences according to methodologies and patient groups. The arguments for or against the use of azithromycin are stated in light of the results of the literature, showing the role of intercurrent factors, such as age, drug consumption, the presence of cancer or periodontal diseases. However, clinical trials are lacking to prove the direct link between the presence of Prevotella spp. and a worsening of COVID- 19, mainly those using azithromycin alone in this indication

Anti-Acne, Antioxidant and Cytotoxic Properties of Ludwigia peploides Leaf Extract

International audienceObjective: This work is the first to investigate the in vitro anti-acne and cytotoxic activities of the leaves of Ludwigia peploides. With its important seasonal biomass production, this plant has great potential in several therapeutic and cosmetic applications.Methods: The antibacterial activity of the extract was screened against a consortium of skin microorganisms that cause acne vulgaris disease, using disc diffusion and broth microdilution methods. The antioxidant activity of methanolic leaf extract of L. peploides was evaluated by DPPH and NBT assays to assess the free radical scavenging activity of L. peploides, which in turn has a great importance related to its role in minimizing the oxidative stress linked to the pathophysiology of diseases like acne vulgaris. Its putative cytotoxicity was examined against human macrophage-like monocytic leukemia (THP-1) and human keratinocytes (HaCaT) cell lines. In addition, antiproliferative activity was screened against B16 cancer cell lines. Results: The extract displayed antioxidant effect by DPPH (IC50= 58 ± 6.0 µg mL-1) and NBT (IC50= 30 ± 2.8 µg mL-1) assays, and it was not toxic on HaCaT cells (IC50 > 200 µg mL-1). A strong inhibitory activity against Propionibacterium acnes (MIC = 1.9 µg mL-1) was registered for the extract, which had a bactericidal effect against Staphylococcus aureus, Staphylococcus epidermidis, and Salmonella enterica. Finally, the extract was shown to have an antiproliferative activity (IC50=5.5 ± 2.3 µgmL-1).Conclusion: The extract displays antioxidant and anti-acne effects as well as inhibition potential of B16 melanoma cells proliferation

Anti-Acne, Antioxidant and Cytotoxic Properties of Ludwigia peploides Leaf Extract

International audienceObjective: This work is the first to investigate the in vitro anti-acne and cytotoxic activities of the leaves of Ludwigia peploides. With its important seasonal biomass production, this plant has great potential in several therapeutic and cosmetic applications.Methods: The antibacterial activity of the extract was screened against a consortium of skin microorganisms that cause acne vulgaris disease, using disc diffusion and broth microdilution methods. The antioxidant activity of methanolic leaf extract of L. peploides was evaluated by DPPH and NBT assays to assess the free radical scavenging activity of L. peploides, which in turn has a great importance related to its role in minimizing the oxidative stress linked to the pathophysiology of diseases like acne vulgaris. Its putative cytotoxicity was examined against human macrophage-like monocytic leukemia (THP-1) and human keratinocytes (HaCaT) cell lines. In addition, antiproliferative activity was screened against B16 cancer cell lines. Results: The extract displayed antioxidant effect by DPPH (IC50= 58 ± 6.0 µg mL-1) and NBT (IC50= 30 ± 2.8 µg mL-1) assays, and it was not toxic on HaCaT cells (IC50 > 200 µg mL-1). A strong inhibitory activity against Propionibacterium acnes (MIC = 1.9 µg mL-1) was registered for the extract, which had a bactericidal effect against Staphylococcus aureus, Staphylococcus epidermidis, and Salmonella enterica. Finally, the extract was shown to have an antiproliferative activity (IC50=5.5 ± 2.3 µgmL-1).Conclusion: The extract displays antioxidant and anti-acne effects as well as inhibition potential of B16 melanoma cells proliferation

Antibacterial activities of natural lichen compounds against Streptococcus gordonii and Porphyromonas gingivalis

International audienceThe oral bacteria not only infect the mouth and reside there, but also travel through the blood and reach distant body organs. If left untreated, the dental biofilm that can cause destructive inflammation in the oral cavity may result in serious medical complications. In dental biofilm, Streptococcus gordonii, a primary oral colonizer, constitutes the platform on which late pathogenic colonizers like Porphyromonas gingivalis, the causative agent of periodontal diseases, will bind. The aim of this study was to determine the antibacterial activity of eleven natural lichen compounds belonging to different chemical families and spanning from linear into cyclic and aromatic structures to uncover new antibiotics which can fight against the oral bacteria. The compounds were screened by broth microdilution assay. Three compounds were shown to have promising antibacterial activities where the depsidone core with certain functional groups constituted the best compound, psoromic acid, with the lowest MICs=11.72 and 5.86μg/mL against S. gordonii and P. gingivalis, respectively. The compounds screened had promising antibacterial activity which might be attributed to some important functional groups as discussed in our study. The best compounds did not induce the death of gingival epithelial carcinoma cells (Ca9-22). These results introduce new compounds having potent antibacterial activities against oral pathogens causing serious medical complications

Bacteroides fragilis derived metabolites, identified by molecular networking, decrease Salmonella virulence in mice model

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