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Listeria monocytogenes: A multipotent bacterium

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Listeria monocytogenes: A multipotent bacterium

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A thorought study of Listeria monocytogenes and its toxicity. Go briefly into its invasion mechanisms and some of the transcription control factors.

A thorought study of Listeria monocytogenes and its toxicity. Go briefly into its invasion mechanisms and some of the transcription control factors.

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Listeria monocytogenes: A multipotent bacterium

  1. 1. Studying the virulence of the pathogenic bacteria Listeria monocytogenes (LM) By JAZIRI Oussama MR1 BMC
  2. 2. Outline Introduction The envasion mechanisms Transcription control factors Treatment
  3. 3. Types Pathogenic bacteria Extracellular Intracellular Multifactorial (toxins): adhesion, colonization, cell destruction. Intracellular survival: Active invasion
  4. 4. Taxonomy  Domain: Bacteria  Kingdom: Eubacteria  Phylum: Firmicutes  Class: Bacilli  Order: Bacillales  Family: Listeriaceae  Genus: Listeria  Species: monocytogenes
  5. 5. Historics  1924-Isolated from rabbit’s blood with mononucleosis  1927-was given its name honoring surgeon lord lister  1929-isolated from human with mononucleosis-like disease
  6. 6. LM characteristics • Gram positive rod •Invasive pathogen • Facultative anaerobe •Catalase +
  7. 7. characteristics • Motile (multi-flagellar) • Psychrotrophic organism • Can grow at 4-45°C • Optimum growth temperature 30-37°C
  8. 8. Characteritics • Tolerates high salt concentration (10-12% NaCl) • It can survive at a pH range of 4.4 – 9.6
  9. 9. Detection: Positive Esculine-test (Quick- check)
  10. 10. Habitat & Association with Foods  Listeria species (spp.) are found in the environment. Isolated from:  Residual waters  Animal feed  Fresh and frozen chicken  Produced and processed foods  uncooked meats and vegetables  Raw milk, Cheese  Faecal matter  The gastro-intestinal tract (even asymptomatic organisms 20%)  Decomposing organic matter  The soil
  11. 11. Lesteriosis  Most susceptible population:  Elderly (>60 years)  Pregnant women: 1 of 3 cases  Immuno-compromised individuals: Eg HIV patients Newborns <1 year) Weak immune system!!
  12. 12. THE ENVASION MECHANISMS
  13. 13. Infection process Listeria monocytogenes (LM) is able to cross all body barriers : Intestinal, blood-brain..
  14. 14. Stages of cell infection • Adhesion at the cellular surface • Entry into cell : bacteria are entrapped into a vacuole → “zipper mechanism” : interaction of rcp-ligand • Escape from the vacuole • Multiplication • Actin polymerization • Intracellular Movement thanks to Actin tail. • Cell to cell spread.
  15. 15. Genome of Listeria L. monocytogenes genome = 2 944 528 bp 0 plasmid 90,3% coding L. Innocua genome = 3 011 209 bp 1 plasmid 90,3% coding L.Innocua shares 2523 orthologous genes with L. monocytogenes,
  16. 16. Virulence genes
  17. 17. The Boss: PrfA  Family of Crp: “cyclic AMP receptors”  First gene expressed  A master regulatory protein; integrates a number of environmental signals and activates a set of key virulence factors during host infection  Activation depends on a lot of conditions/factors..
  18. 18. InlA E-cadherin
  19. 19. Inl.A – E.cadherin InlA- E.cadherin InlA # E.cadherin
  20. 20. LLO PLCs Entry Escape
  21. 21. PI-PLC PC-PLC LLO
  22. 22. Vacuole Lysis  Listeriolysin O (LLO)  Fam: Cholesterol-Dependant Cytolysin (CDC)  LLO: Major & first identified virulence factor, its ability is to create pores in the membranes  PI-PLC & PC-PLC are speciphic phospholipases  help LLO with vacuole lysis
  23. 23. Fig 7. Schematic representation of LLO membrane disruptive action.
  24. 24. ActA+Arp 2/3 complex Escape PLC Actin Based Motility
  25. 25. Actin-based motility  ActA forms a complex with Arp2/3  Actin molecules are added to the free barbed ends of the complex = Filaments
  26. 26. Act A Arp2/3 complex Actin polymerization Actin-based Motility Tie it together
  27. 27. Control factors(Conditions) governing the transcription  The glutathione uptake: the more = the more  The environmental cellobiose: the less = the more  Sigma factor (σ): regulator, protector and very essential inside the intestine, controls PrfA  VirR/S: Coordinatior of surface components modification and in the antimicrobial resistance: inhances resistance + agility
  28. 28.  CodY: regulator of metabolism inside the host cells; capable of controling PrfA  MogR: repressor of flagellin formation; depending on the temperature
  29. 29. Novelties! The overlapping lasRNA can act as a negative regulator for genes encoded on the opposite strand, but it can also be used as an mRNA for the genes encoded on the same strand
  30. 30. How to Treat your Listeria  Ampicillin  Gentamicin  Chloramphenicol
  31. 31. Antibiotics  Ampicilin  Inhibits the third and final stage of bacterial cell wall synthesis  Gentamicin  It inhibits metabolic activities in the bacteria. It binds to a site on the bacterial ribosome, causing the genetic code to be misread  Chloramphenicol  Stops bacterial growth by inhibiting the enzyme “peptide transferase”
  32. 32. THANKS!

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