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
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. 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!!
15. 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.
16. 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,
18. 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..
24. 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
25. Fig 7. Schematic representation of LLO membrane
disruptive action.
32. 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
33. CodY: regulator of metabolism inside the host
cells; capable of controling PrfA
MogR: repressor of flagellin formation;
depending on the temperature
34. 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
35. How to Treat your Listeria
Ampicillin
Gentamicin
Chloramphenicol
36. 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”