Personne :
Fliss, Ismaïl

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Structures organisationnelles
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Université Laval. Département des sciences des aliments
Identifiant Canadiana

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Voici les éléments 1 - 10 sur 12
  • Publication
    Accès libre
    Structure-activity studies of the bacteriocin bactofencin A and its interaction with the bacterial membrane
    (American Chemical Society, 2018-12-12) Biron, Éric; Fliss, Ismaïl; Bédard, François
    The antimicrobial peptide bactofencin A is an unmodified non-pediocin-like bacteriocin that inhibits several clinically relevant pathogens, including Listeria monocytogenes and Staphylococcus aureus. Here we report the synthesis and structure–activity relationship studies of bactofencin A and novel analogues thereof. Synthetic bactofencin A was a potent inhibitor of L. monocytogenes (MIC = 8.0 μM) and S. aureus (MIC = 4.0 μM), similar to the bacteriocin produced naturally by Lactobacillus salivarius. Of particular interest is the fact that linear analogues lacking the disulfide bond found in bactofencin A were as potent and also active against several strains of methicillin-resistant S. aureus (MRSA) and one strain of vancomycin-resistant S. aureus (VRSA). Supported by the structure–activity relationship study, investigation of the interaction of bactofencin A with bacterial membrane by molecular dynamics simulations showed the importance of the positively charged N-terminal tail for peptide–membrane interaction. These results suggest that the C-terminal macrocycle is involved in target protein binding and bacterial growth inhibition.
  • Publication
    Lasso-inspired peptides with distinct antibacterial mechanisms
    (Springer-Verlag Wien, 2014-12-04) Biron, Éric; Gomaa, Ahmed; Fliss, Ismaïl; Bédard, François; Subirade, Muriel; Hammami, Riadh
    Abstract Microcin J25 (MccJ25) is an antibacterial peptide with a peculiar molecular structure consisting of 21 amino acids and a unique lasso topology that makes it highly stable. We synthesized various MccJ25-derived peptides that retained some of the inhibitory activity of the native molecule against Salmonella enterica and Escherichia coli. Of the tested peptides, C1, 7-21C and WK_7-21 were the most inhibitory peptides (MIC = 1–250 µM), but all three were less potent than MccJ25. While MccJ25 was not active against Gram-positive bacteria, the three derived peptides were slightly inhibitory to Gram-positive bacteria (MIC = 250 µM). At 5 µM, C1, 7-21C and WK_7-21 reduced E. coli RNA polymerase activity by respectively, 23.4, 37.4 and 65.0 %. The MccJ25 and its derived peptides all appeared to affect the respiratory apparatus of S. enterica. Based on circular dichroism and FTIR spectroscopy, the peptides also interact with bacterial membrane phospholipids. These results suggest the possibility of producing potent MccJ25-derived peptides lacking the lasso structure. Keywords Antimicrobial peptides · Microcin J25 · Solid phase peptide synthesis · Antibacterial activity · Mode of action
  • Publication
    Collagencin, an antibacterial peptide from fish collagen : activity, structure and interaction dynamics with membrane
    (Elsevier, 2016-03-30) Biron, Éric; Gomaa, Ahmed; Fliss, Ismaïl; Beaulieu, Lucie; Bédard, François; Subirade, Muriel; Ennaas, Nadia; Hammami, Riadh
    In this study, we first report characterization of collagencin, an antimicrobial peptide identified from fish collagen hydrolysate. The peptide completely inhibited the growth of Staphylococcus aureus at 1.88 mM. Although non-toxic up to 470 μM, collagencin was hemolytic at higher concentrations. The secondary structure of collagencin was mainly composed by β-sheet and β-turn as determined by CD measurements and molecular dynamics. The peptide is likely to form β-sheet structure under hydrophobic environments and interacts with both anionic (phosphatidylglycerol) and zwitterionic (phosphoethanolamine and phosphatidylcholine) lipids as shown with CD spectroscopy and molecular dynamics. The peptide formed several hydrogen bonds with both POPG and POPE lipids and remained at membrane–water interface, suggesting that collagencin antibacterial action follows a carpet mechanism. Collagenous fish wastes could be processed by enzymatic hydrolysis and transformed into products of high value having functional or biological properties. Marine collagens are a promising source of antimicrobial peptides with new implications in food safety and human health.
  • Publication
    Accès libre
    Insights in the development and uses of alternatives to antibiotic growth promoters in poultry and swine production
    (MDPI AG, 2022-06-02) Biron, Éric; Rahman, Md Ramim Tanver; Fliss, Ismaïl
    The overuse and misuse of antibiotics has contributed to the rise and spread of multidrugresistant bacteria. To address this global public health threat, many countries have restricted the use of antibiotics as growth promoters and promoted the development of alternatives to antibiotics in human and veterinary medicine and animal farming. In food-animal production, acidifiers, bacteriophages, enzymes, phytochemicals, probiotics, prebiotics, and antimicrobial peptides have shown hallmarks as alternatives to antibiotics. This review reports the current state of these alternatives as growth-promoting factors for poultry and swine production and describes their mode of action. Recent findings on their usefulness and the factors that presently hinder their broader use in animal food production are identified by SWOT (strength, weakness, opportunity, and threat) analysis. The potential for resistance development as well as co- and cross-resistance with currently used antibiotics is also discussed. Using predetermined keywords, we searched specialized databases including Scopus, Web of Science, and Google Scholar. Antibiotic resistance cannot be stopped, but its spreading can certainly be hindered or delayed with the development of more alternatives with innovative modes of action and a wise and careful use of antimicrobials in a One Health approach.
  • Publication
    Commercial dairy cow milk microRNAs resist digestion under simulated gastrointestinal tract conditions
    (Charles C. Thomas, Publisher, 2016-10-05) Gilbert, Caroline; Lee, Chan Ho C.; Savard, Patricia; Benmoussa, Abderrahim; Fliss, Ismaïl; Provost, Patrick; Laffont, Benoit; Laugier, Jonathan; Boilard, Éric
    Background: MicroRNAs are small, gene-regulatory noncoding RNA species present in large amounts in milk, where they seem to be protected against degradative conditions, presumably because of their association with exosomes. Objective: We monitored the relative stability of commercial dairy cow milk microRNAs during digestion and examined their associations with extracellular vesicles (EVs). Methods: We used a computer-controlled, in vitro, gastrointestinal model TNO intestinal model-1 (TIM-1) and analyzed, by quantitative polymerase chain reaction, the concentration of 2 microRNAs within gastrointestinal tract compartments at different points in time. EVs within TIM-1 digested and nondigested samples were studied by immunoblotting, dynamic light scattering, quantitative polymerase chain reaction, and density measurements. Results: A large quantity of dairy milk Bos taurus microRNA-223 (bta-miR-223) and bta-miR-125b (∼109–1010 copies/300 mL milk) withstood digestion under simulated gastrointestinal tract conditions, with the stomach causing the most important decrease in microRNA amounts. A large quantity of these 2 microRNAs (∼108–109 copies/300 mL milk) was detected in the upper small intestine compartments, which supports their potential bioaccessibility. A protocol optimized for the enrichment of dairy milk exosomes yielded a 100,000 × g pellet fraction that was positive for the exosomal markers tumor susceptibility gene-101 (TSG101), apoptosis-linked gene 2–interacting protein X (ALIX), and heat shock protein 70 (HSP70) and containing bta-miR-223 and bta-miR-125b. This approach, based on successive ultracentrifugation steps, also revealed the existence of ALIX−, HSP70−/low, and TSG101−/low EVs larger than exosomes and 2–6 times more enriched in bta-miR-223 and bta-miR-125b (P < 0.05). Conclusions: Our findings indicate that commercial dairy cow milk contains numerous microRNAs that can resist digestion and are associated mostly with ALIX−, HSP70−/low, and TSG101−/low EVs. Our results support the existence of interspecies transfer of microRNAs mediated by milk consumption and challenge our current view of exosomes as the sole carriers of milk-derived microRNAs.
  • Publication
    Accès libre
    Gastrointestinal stability and cytotoxicity of bacteriocins from gram-positive and gram-negative bacteria : a comparative in vitro study
    (Frontiers Media, 2022-01-25) Biron, Éric; Zirah, Séverine; Rebuffat, Sylvie; Soltani, Samira; Couture, Frédéric; Fliss, Ismaïl; Subirade, Muriel; Boutin, Yvan.
    Bacteriocins are receiving increased attention as potent candidates in food preservation and medicine. Although the inhibitory activity of bacteriocins has been studied widely, little is known about their gastrointestinal stability and toxicity toward normal human cell lines. The aim of this study was to evaluate the gastrointestinal stability and activity of microcin J25, pediocin PA-1, bactofencin A and nisin using in vitro models. In addition cytotoxicity and hemolytic activity of these bacteriocins were investigated on human epithelial colorectal adenocarcinoma cells (Caco-2) and rat erythrocytes, respectively. Pediocin PA-1, bactofencin A, and nisin were observed to lose their stability while passing through the gastrointestinal tract, while microcin J25 is only partially degraded. Besides, selected bacteriocins were not toxic to Caco-2 cells, and integrity of cell membrane was observed to remain unaffected in presence of these bacteriocins at concentrations up to 400 μg/mL. In hemolysis study, pediocin PA-1, bactofencin A, and nisin were observed to lyse rat erythrocytes at concentrations higher than 50 μg/mL, while microcin J25 showed no effect on these cells. According to data indicating gastrointestinal degradation and the absence of toxicity of pediocin PA-1, bactofencin A, and microcin J25 they could potentially be used in food or clinical applications.
  • Publication
    Accès libre
    In vitro assessment of skin sensitization, irritability and toxicity of bacteriocins and reuterin for possible topical applications
    (Nature Publishing Group, 2022-03-17) Biron, Éric; Frédéric Couture; Soltani, Samira; Fliss, Ismaïl; Subirade, Muriel; Boutin, Yvan.
    Bacteriocins and reuterin are promising antimicrobials for application in food, veterinary, and medical sectors. In the light of their high potential for application in hand sanitizer, we investigated the skin toxicity of reuterin, microcin J25, pediocin PA-1, bactofencin A, and nisin Z in vitro using neutral red and LDH release assays on NHEK cells. We determined their skin sensitization potential using the human cell line activation test (h-CLAT). Their skin irritation potential was measured on human epidermal model EpiDerm™. We showed that the viability and membrane integrity of NHEK cells remained unaltered after exposure to bacteriocins and reuterin at concentrations up to 400 µg/mL and 80 mg/mL, respectively. Furthermore, microcin J25 and reuterin showed no skin sensitization at concentrations up to 100 µg/mL and 40 mg/mL, respectively, while pediocin PA-1, bactofencin A, and nisin Z caused sensitization at concentrations higher than 100 µg/mL. Tissue viability was unafected in presence of bacteriocins and reuterin at concentrations up to 200 µg/mL and 40 mg/ mL, respectively, which was confrmed by measuring cytokine IL-1α and IL-8 levels and by histological analysis. In conclusion, the current study provides scientifc evidence that some bacteriocins and reuterin, could be safely applied topically as sanitizers at recommended concentrations
  • Publication
    Accès libre
    Bacteriocins as a new generation of antimicrobials : toxicity aspects and regulations
    (Elsevier, 2020-09-02) Ben Said, Laila; Biron, Éric; Soltani, Samira; Gaudreau, Hélène; Fliss, Ismaïl; Bédard, François; Hammami, Riadh
    In recent decades, bacteriocins have received substantial attention as antimicrobial compounds. Although bacteriocins have been predominantly exploited as food preservatives, they are now receiving increased attention as potential clinical antimicrobials and as possible immune-modulating agents. Infections caused by antibiotic-resistant bacteria have been declared as a global threat to public health. Bacteriocins represent a potential solution to this worldwide threat due to their broad- or narrow-spectrum activity against antibiotic-resistant bacteria. Notably, despite their role in food safety as natural alternatives to chemical preservatives, nisin remains the only bacteriocin legally approved by regulatory agencies as a food preservative. Moreover, insufficient data on the safety and toxicity of bacteriocins represent a barrier against the more widespread use of bacteriocins by the food and medical industry. Here, we focus on the most recent trends relating to the application of bacteriocins, their toxicity and impacts.
  • Publication
    Monoclonal antibodies raised against native major capsid proteins of lactococcal c2-like bacteriophages
    (American Society for Microbiology, 1998-08-11) Simard, Ronald-E.; Moineau, Sylvain; Fliss, Ismaïl; Chibani Azaïez, Sandra.
    Phage Q38, a representative member of the c2 species, was purified by CsCl gradient and used to immunize BALB/c mice. Monoclonal antibodies (MAbs) were raised and then characterized by enzyme-linked immunosorbent assay. Two MAbs of isotype immunoglobulin G2a, designated 2A5 and 6G7, reacted only with phages belonging to the c2 species and not with phages of the 936 and P335 species, with a Lactococcus lactis cell extract, or with phage DNA. Immunoelectron microscopy showed that both MAbs recognized only phage head proteins. They did not react with any denatured phage proteins in Western blot assays. However, when the nitrocellulose membranes were treated with a Triton-based buffer to assist in protein renaturation, MAbs 2A5 and 6G7 recognized the two major capsid proteins with molecular masses of 80 and 170 kDa. Competitive inhibition tests showed that the two MAbs bind to overlapping epitopes. These MAbs may be a useful tool for monitoring c2 bacteriophages during dairy fermentation and in genetic studies
  • Publication
    Accès libre
    Bacteriocin-based synergetic consortia : a promising strategy to enhance antimicrobial activity and broaden the spectrum of inhibition
    (ASM Press, 2022-02-16) Ben Said, Laila; Biron, Éric; Soltani, Samira; Fliss, Ismaïl; Subirade, Muriel
    Bacteria-derived natural antimicrobial compounds such as bacteriocins, reruterin, and organic acids have recently received substantial attention as food preservatives or therapeutic alternatives in human or animal sectors. This study aimed to evaluate the antimicrobial activity of different bacteria-derived antimicrobials, alone or in combination, against a large panel of Gram-negative and Gram-positive bacteria. Bacteriocins, including microcin J25, pediocin PA-1, nisin Z, and reuterin, were investigated alone or in combination with lactic acid and citric acid, using a checkerboard assay. Concentrations were selected based on predetermined MICs against Salmonella enterica subsp. enterica serovar Newport ATCC 6962 and Listeria ivanovii HPB28 as Gram-negative and Gram-positive indicator strains, respectively. The results demonstrated that the combination of microcin J25 + citric acid + lactic acid; microcin J25 + reuterin + citric acid; and microcin J25 + reuterin + lactic acid tested against S. Newport ATCC 6962 showed synergistic effects (FIC index = 0.5). Moreover, a combination of pediocin PA-1 + citric acid + lactic acid; and reuterin + citric acid + lactic acid against L. ivanovii HPB28 showed a partially synergistic interactions (FIC index = 0.75). Nisin Z exerted a partially synergistic effect in combination with acids (FIC index = 0.625 -0.75), whereas when it was combined with reuterin or pediocin PA-1, it showed additive effects (FIC index = 1) against L. ivanovii HPB28. The inhibitory activity of synergetic consortia were tested against a large panel of Gram-positive and Gram-negative bacteria. According to our results, combining different antimicrobials with different mechanisms of action led to higher potency and a broad spectrum of inhibition, including multidrug-resistance pathogens.