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Michel Hébraud - One of the best experts on this subject based on the ideXlab platform.
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Anti-bacterial and anti-adherence activities of a probiotic strain of Lactobacillus paracasei subsp. paracasei against Listeria monocytogenes
International Journal of Applied Microbiology and Biotechnology Research, 2014Co-Authors: F. Bendali, Michel Hébraud, D. SadounAbstract:Lactobacilli are very ubiquitous, frequently associated to h uman microbial flora and foodstuffs ; where they have being observed to accomplish various protective roles against adverse microorganisms. A human strain of Lactobacillus paracasei subsp. paracasei originally isolated from newborn faeces was investigated o n its anti - Listerial activities. Using intestinal Caco - 2 cell line in an in vitro model and abiotic surfaces, stainless steel and Teflon (polytetrafluoroethylene) which are the most largely used materials in food ind ustry, i t was observed that this strain exhibited adherence and anti - adherence properties. The inhibitory effects of this strain on the adherence of Listeria monocytogenes were determined. A decrease in the number of adhering pathogen cells was observed, using either pre - incubation or co - incubat ion of the pathogen with Lb. paracasei . Moreover, the anti - Listerial and anti - adherence activities of its cell - free supernatant were examined. A n antibacterial activity related to the production of a bacteriocin - like substance and a d isplacement of the pat hogen from all the surfaces (Caco - 2 cell line, stainless steel and Teflon ) were registered. Together, these findings suggest that this strain could be used to prevent colonization of the gastrointestinal tract and the food - contact surfaces by L isteria mono cytogenes.
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Molecular biology of surface colonization by Listeria monocytogenes: an additional facet of an opportunistic Gram-positive foodborne pathogen
Environmental Microbiology, 2011Co-Authors: Sandra Renier, Michel Hébraud, Mickael DesvauxAbstract:The opportunistic and facultative intracellular pathogenic bacterium Listeria monocytogenes causes a rare but severe foodborne disease called listeriosis, the outcome of which can be fatal. The infection cycle and key virulence factors are now well characterized in this species. Nonetheless, this knowledge has not prevented the re-emergence of listeriosis, as recently reported in several European countries. Listeria monocytogenes is particularly problematic in the food industry since it can survive and multiply under conditions frequently used for food preservation. Moreover, this foodborne pathogen also forms biofilms, which increase its persistence and resistance in industrial production lines, leading to contamination of food products. Significant differences have been reported regarding the ability of different isolates to form biofilms, but no clear correlation can be established with serovars or lineages. The architecture of Listerial biofilms varies greatly from one strain to another as it ranges from bacterial monolayers to the most recently described network of knitted chains. While the role of polysaccharides as part of the extracellular matrix contributing to Listerial biofilm formation remains elusive, the importance of eDNA has been demonstrated. The involvement of flagella in biofilm formation has also been pointed out, but their exact role in the process remains to be clarified because of conflicting results. Two cell-cell communication systems LuxS and Agr have been shown to take part in the regulation of biofilm formation. Several additional molecular determinants have been identified by functional genetic analyses, such as the (p)ppGpp synthetase RelA and more recently BapL. Future directions and questions about the molecular mechanisms of biofilm formation in L. monocytogenes are further discussed, such as correlation between clonal complexes as revealed by MLST and biofilm formation, the swarming over swimming regulation hypothesis regarding the role of the flagella, and the involvement of microbial surface components recognizing adhesive matrix molecules in the colonization of abiotic and biotic surfaces.
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Bacterial secreted proteins: secretory mechanisms and role in pathogenesis
2009Co-Authors: Mickael Desvaux, Michel HébraudAbstract:As a monoderm prokaryote, protein secretion systems in Listeria monocytogenes are distinct from those encounter in diderm bacteria, still they remain the gates for expressing protein functions outside the intracellular bacterial cell compartment. Despite the fact that protein secretion is a key factor in virulence of a pathogen, fewer studies have been dedicated to pathogenic Gram-positive bacteria compared to Gram-negative bacteria and L. monocytogenes is no exception. Among the six protein secretion systems identified in L. monocytogenes, only proteins putatively translocated via the Sec pathway are indisputably involved in bacterial virulence. The 16 secreted virulence effectors characterized to date are either (i) associated with the cytoplasmic membrane, i.e. as integral membrane proteins or lipoproteins, (ii) associated with the cell wall, i.e. covalently in a sortase-dependent manner or via cell-wall binding domains, or (iii) released in the extracellular milieu. Identification of several candidates as putative secreted virulence factors as well as the availability in the near future of a large amount of Listeria genomic data from different sequencing projects promise a very exciting time in the field of Listerial protein secretion and should provide further insights into how L. monocytogenes interacts with its biotic or abiotic surroundings. Introduction The genus Listeria is hitherto circumscribed to only six species namely L. monocytogenes, L. in-nocua, L. seeligeri, L. welshimeri, L. ivanovii and L. grayi (Vaneechoutte et al., 1998); it is worth
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kinetic of production and mode of action of the lactobacillus paracasei subsp paracasei anti Listerial bacteriocin an algerian isolate
Lwt - Food Science and Technology, 2008Co-Authors: Farida Bendali, Michel Hébraud, Brigitte Gaillardmartinie, Djamila SadounAbstract:Abstract Lactobacillus paracasei subsp. paracasei was isolated in our laboratory from breast-fed newborn faeces and identified phenotypically and genotypically. The strain was able to produce a bacteriocin-like substance active towards Listerial strains ( Listeria innocua CLIP 74915 and Listeria monocytogenes EGDe). The maximum production of the substance by producing strain was detected in the late logarithmic growth phase (14 h in MRS and 18 h in BHI broths). It displayed bactericidal mode of action with leakage of cellular content (K + and ATP) leading to cell lysis as secondary effect. A reduction of about 5 log with 35.7 ± 0.2% of cell lysis and of about 4 log with 82.0 ± 0.3% of cell lysis were observed, respectively, in a phosphate buffer and BHI suspensions. This was further demonstrated by electron microscopy that showed severe modifications in the cell morphology with a concomitant lysis.
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Kinetic of production and mode of action of the Lactobacillus paracasei subsp. paracasei anti-Listerial bacteriocin, an Algerian isolate
LWT - Food Science and Technology, 2008Co-Authors: Farida Bendali, Michel Hébraud, Brigitte Gaillard-martinie, Djamila SadounAbstract:Lactobacillus paracasei subsp. paracasei was isolated in our laboratory from breast-fed newborn faeces and identified phenotypically and genotypically. The strain was able to produce a bacteriocin-like substance active towards Listerial strains (Listenia innocua CLIP 74915 and Listeria monocytogenes EGDe). The maximum production of the substance by producing strain was detected in the late logarithmic growth phase (14 h in MRS and 18 h in BHI broths). It displayed bactericidal mode of action with leakage of cellular content (K+ and ATP) leading to cell lysis as secondary effect. A reduction of about 5 log with 35.7 +/- 0.2% of cell lysis and of about 4 log with 82.0 +/- 0.3% of cell lysis were observed, respectively, in a phosphate buffer and BHI suspensions. This was further demonstrated by electron microscopy that showed severe modifications in the cell morphology with a concomitant lysis. (C) 2008 Swiss Society of Food Science and Technology.
Djamila Sadoun - One of the best experts on this subject based on the ideXlab platform.
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kinetic of production and mode of action of the lactobacillus paracasei subsp paracasei anti Listerial bacteriocin an algerian isolate
Lwt - Food Science and Technology, 2008Co-Authors: Farida Bendali, Michel Hébraud, Brigitte Gaillardmartinie, Djamila SadounAbstract:Abstract Lactobacillus paracasei subsp. paracasei was isolated in our laboratory from breast-fed newborn faeces and identified phenotypically and genotypically. The strain was able to produce a bacteriocin-like substance active towards Listerial strains ( Listeria innocua CLIP 74915 and Listeria monocytogenes EGDe). The maximum production of the substance by producing strain was detected in the late logarithmic growth phase (14 h in MRS and 18 h in BHI broths). It displayed bactericidal mode of action with leakage of cellular content (K + and ATP) leading to cell lysis as secondary effect. A reduction of about 5 log with 35.7 ± 0.2% of cell lysis and of about 4 log with 82.0 ± 0.3% of cell lysis were observed, respectively, in a phosphate buffer and BHI suspensions. This was further demonstrated by electron microscopy that showed severe modifications in the cell morphology with a concomitant lysis.
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Kinetic of production and mode of action of the Lactobacillus paracasei subsp. paracasei anti-Listerial bacteriocin, an Algerian isolate
LWT - Food Science and Technology, 2008Co-Authors: Farida Bendali, Michel Hébraud, Brigitte Gaillard-martinie, Djamila SadounAbstract:Lactobacillus paracasei subsp. paracasei was isolated in our laboratory from breast-fed newborn faeces and identified phenotypically and genotypically. The strain was able to produce a bacteriocin-like substance active towards Listerial strains (Listenia innocua CLIP 74915 and Listeria monocytogenes EGDe). The maximum production of the substance by producing strain was detected in the late logarithmic growth phase (14 h in MRS and 18 h in BHI broths). It displayed bactericidal mode of action with leakage of cellular content (K+ and ATP) leading to cell lysis as secondary effect. A reduction of about 5 log with 35.7 +/- 0.2% of cell lysis and of about 4 log with 82.0 +/- 0.3% of cell lysis were observed, respectively, in a phosphate buffer and BHI suspensions. This was further demonstrated by electron microscopy that showed severe modifications in the cell morphology with a concomitant lysis. (C) 2008 Swiss Society of Food Science and Technology.
Colin Hill - One of the best experts on this subject based on the ideXlab platform.
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Inhibitory activity of Lactobacillus plantarum LMG P-26358 against Listeria innocua when used as an adjunct starter in the manufacture of cheese
Microbial Cell Factories, 2011Co-Authors: Susan Mills, Colin Hill, Lmariela Serrano, Carmel Griffin, Paula M O'connor, Gwenda Schaad, Chris Bruining, Rpaul Ross, Wilco C MeijerAbstract:Lactobacillus plantarum LMG P-26358 isolated from a soft French artisanal cheese produces a potent class IIa bacteriocin with 100% homology to plantaricin 423 and bacteriocidal activity against Listeria innocua and Listeria monocytogenes . The bacteriocin was found to be highly stable at temperatures as high as 100°C and pH ranges from 1-10. While this relatively narrow spectrum bacteriocin also exhibited antimicrobial activity against species of enterococci, it did not inhibit dairy starters including lactococci and lactobacilli when tested by well diffusion assay (WDA). In order to test the suitability of Lb. plantarum LMG P-26358 as an anti-Listerial adjunct with nisin-producing lactococci, laboratory-scale cheeses were manufactured. Results indicated that combining Lb. plantarum LMG P-26358 (at 10^8 colony forming units (cfu)/ml) with a nisin producer is an effective strategy to eliminate the biological indicator strain, L. innocua . Moreover, industrial-scale cheeses also demonstrated that Lb. plantarum LMG P-26358 was much more effective than the nisin producer alone for protection against the indicator. MALDI-TOF mass spectrometry confirmed the presence of plantaricin 423 and nisin in the appropriate cheeses over an 18 week ripening period. A spray-dried fermentate of Lb. plantarum LMG P-26358 also demonstrated potent anti-Listerial activity in vitro using L. innocua . Overall, the results suggest that Lb. plantarum LMG P-26358 is a suitable adjunct for use with nisin-producing cultures to improve the safety and quality of dairy products.
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role of the glutamate decarboxylase acid resistance system in the survival of Listeria monocytogenes lo28 in low ph foods
Journal of Food Protection, 2001Co-Authors: Paul D Cotter, Karen Oreilly, Colin HillAbstract:The glutamate decarboxylase (GAD) acid resistance system of the foodborne pathogen Listeria monocytogenes plays a major role in its survival at low pH. It was found that survival of the wild-type strain, LO28, in acidified reconstituted skim milk, diluted to reduce free glutamate levels, improves in response to supplementation with monosodium glutamate. A mutant, in which the two Listerial GAD homologs have been deleted (and in which there is no discernible GAD activity), did not respond to glutamate supplementation and displayed greatly enhanced sensitivity in a number of low pH foods, even when levels of free glutamate were as low as 0.22 mM. We thus show that the GAD system plays a major role in the survival of L. monocytogenes in acidic foods even when levels of free glutamate are low.
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analysis of the role of opuc an osmolyte transport system in salt tolerance and virulence potential of Listeria monocytogenes
Applied and Environmental Microbiology, 2001Co-Authors: Roy D Sleator, Jeroen Wouters, Cormac G M Gahan, Tjakko Abee, Colin HillAbstract:The success of Listeria monocytogenes as a food-borne pathogen owes much to its ability to survive a variety of stresses, both in the external environment prior to ingestion and subsequently within the animal host. Growth at high salt concentrations and low temperatures is attributed mainly to the accumulation of organic solutes such as glycine betaine and carnitine. We utilized a novel system for generating chromosomal mutations (based on a lactococcal pWVO1-derived Ori+ RepA− vector, pORI19) to identify a Listerial OpuC homologue. Mutating the operon in two strains of L. monocytogenes revealed significant strain variation in the observed activity of OpuC. Radiolabeled osmolyte uptake studies, together with growth experiments in defined media, linked OpuC to carnitine and glycine betaine uptake in Listeria. We also investigated the role of OpuC in contributing to the growth and survival of Listeria in an animal (murine) model of infection. Altering OpuC resulted in a significant reduction in the ability of Listeria to colonize the upper small intestine and cause subsequent systemic infection following peroral inoculation.
José A. Vázquez-boland - One of the best experts on this subject based on the ideXlab platform.
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Epistatic control of intrinsic resistance by virulence genes in Listeria
PLoS Genetics, 2018Co-Authors: Mariela Scortti, Lei Han, Sonsiray Alvarez, Alexandre Leclercq, Alexandra Moura, Marc Lecuit, José A. Vázquez-bolandAbstract:Elucidating the relationships between antimicrobial resistance and virulence is key to understanding the evolution and population dynamics of resistant pathogens. Here, we show that the susceptibility of the gram-positive bacterium Listeria monocytogenes to the antibiotic fosfomycin is a complex trait involving interactions between resistance and virulence genes and the environment. We found that a FosX enzyme encoded in the Listerial core genome confers intrinsic fosfomycin resistance to both pathogenic and non-pathogenic Listeria spp. However, in the genomic context of the pathogenic L. monocytogenes, FosX-mediated resistance is epistatically suppressed by two members of the PrfA virulence regulon, hpt and prfA, which upon activation by host signals induce increased fosfomycin influx into the bacterial cell. Consequently, in infection conditions, most L. monocytogenes isolates become susceptible to fosfomycin despite possessing a gene that confers high-level resistance to the drug. Our study establishes the molecular basis of an epistatic interaction between virulence and resistance genes controlling bacterial susceptibility to an antibiotic. The reported findings provide the rationale for the introduction of fosfomycin in the treatment of Listeria infections even though these bacteria are intrinsically resistant to the antibiotic in vitro.
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The PrfA virulence regulon.
Microbes and Infection, 2007Co-Authors: Mariela Scortti, Héctor J. Monzó, Lizeth Lacharme-lora, Deborah A. Lewis, José A. Vázquez-bolandAbstract:The PrfA protein, a member of the Crp/Cap-Fnr family of bacterial transcription factors, controls the expression of key virulence determinants of the facultative intracellular pathogen Listeria monocytogenes. Each of the steps of the Listerial intracellular infection cycle-host cell invasion, phagosomal escape, cytosolic replication, and direct cell-to-cell spread-is mediated by products of the PrfA regulon. Only 10 of the 2853 genes of the L. monocytogenes EGDe genome have been confirmed as bona fide (directly regulated) members of this regulon, a number surprisingly small given the apparent complexity of Listerial intracellular parasitism. PrfA activates transcription by binding as a dimer to a palindromic promoter element of canonical sequence tTAACanntGTtAa, with seven invariant nucleotides (in capitals) and a two-mismatch tolerance. PrfA integrates a number of environmental and bacteria-derived signals to ensure the correct spatio-temporal and niche-adapted expression of the regulon, with maximum induction in the host cell cytosol and repression in the environmental habitat. Regulation operates through changes in PrfA activity-presumably by cofactor-mediated allosteric shift-and concentration, and involves transcriptional, translational and post-translational control mechanisms. There is evidence that PrfA exerts a more global influence on L. monocytogenes physiology via indirect mechanisms.
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Hpt, a bacterial homolog of the microsomal glucose- 6-phosphate translocase, mediates rapid intracellular proliferation in Listeria
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Isabel Chico-calero, Werner Goebel, Mónica Suárez, Bruno Gonzalez-zorn, Mariela Scortti, Jörg Slaghuis, José A. Vázquez-bolandAbstract:Efficient replication in vivo is essential for a microparasite to colonize its host and the understanding of the molecular mechanisms by which microbial pathogens grow within host tissues can lead to the discovery of novel therapies to treat infection. Here we present evidence that the foodborne bacterial pathogen Listeria monocytogenes, a facultative intracellular parasite, exploits hexose phosphates (HP) from the host cell as a source of carbon and energy to fuel fast intracellular growth. HP uptake is mediated by Hpt, a bacterial homolog of the mammalian translocase that transports glucose-6-phosphate from the cytosol into the endoplasmic reticulum in the final step of gluconeogenesis and glycogenolysis. Expression of the Hpt permease is tightly controlled by the central virulence regulator PrfA, which upon entry into host cells induces a set of virulence factors required for Listerial intracellular parasitism. Loss of Hpt resulted in impaired Listerial intracytosolic proliferation and attenuated virulence in mice. Hpt is the first virulence factor to be identified as specifically involved in the replication phase of a facultative intracellular pathogen. It is also a clear example of how adaptation to intracellular parasitism by microbial pathogens involves mimicry of physiological mechanisms of their eukaryotic host cells.
Achim Schmalenberger - One of the best experts on this subject based on the ideXlab platform.
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Inhibition of Listeria monocytogenes growth on fresh-cut produce with thyme essential oil and essential oil compound verbenone
Postharvest Biology and Technology, 2016Co-Authors: Johann Scollard, Oisin Mcmanamon, Achim SchmalenbergerAbstract:Abstract The anti-Listerial effectiveness of thyme essential oil (EO) and EO compounds camphor and verbenone was examined on fresh-cut lettuce, cantaloupe melon and pineapple with modified atmospheres and air in model packages at 4 and 8 °C. Listeria monocytogenes was found to be able to survive and grow in all atmospheres on melon and lettuce. However, on pineapple lowest survival was identified, presumably due to product pH. Thyme EO demonstrated the best anti-Listerial effect, although direct application of the EO compromised product appearance. While camphor showed no anti-Listerial effects, verbenone was found to have anti-Listerial properties and maintained high sensory acceptance in fresh-cut fruit. The high growth rates of L. monocytogenes on melon were significantly reduced with the application of verbenone while being completely eliminated on pineapple. The use of thyme EO and verbenone as an antimicrobial dip was successfully applied to reduce growth of Listeria on fresh-cut melon and eliminate growth on pineapple; however growth-reduction was less pronounced in melon when compared to a conventional chlorine dip. Further research will be necessary to optimise conditions in fresh-cut produce treatments with natural products including verbenone and thyme EO to replace current chlorine treatments for improved food safety.
