Med Micro 11 - Listeria Flashcards
What do we mean by virulence is multifactorial?
More than one virulence factor
What do we mean by virulence is multidimensional?
Gene regulation
How is the “virulence process” represented in this diagram??
it is multifactorial and multidimensional! Which is which? Multidimensional means they are turned on and off at different times
L. monocytogenes characteristics
Gram + rod; opportunistic intracellular pathogen
Listeriosis
Infection from raw contaminated food; Clinical features range from mild influenza-like symptoms to meningitis and/or meningoencephalitis accompanied by septicemia. Infection of fetus is common
Why is Listeria called a public health problem?
Because we can’t eradicate it
What is another example of a public health problem?
Antibiotic resistance. Cannot win (yet)
Why is Listeria so hard to eradicate?
It has such a large reservoir - animals and animal products (esp cows and dairy).
What type of transmission is Listeria?
It is carried in food, so vehicle! (not zoonotic)
Natural habitats and incidence of disease
Listera is carried by 5-10% human population; true incidence is not know. Leading cause of death in food borne bacterial pathogens
Who is most affected by listeria?
affects primarily pregnant women, fetus, newborns, and adults with weakened immune systems. This means we fight it with cell-mediated response
Why is it important to know the symptoms of Listeriosis?
Need to be able to diagnose
Pathogenesis
Normally, immune system contains the infection; adults with no history have T cells primed by listeria antigens; generate biofilm, esp in response to bile at 37C; able to cross the intestinal barrier, the blood-brain barrier, and the placental barrier
Growth at low temperature
You can achieve full growth at 4C! Problem even with refrigerated food.
Describe the quorum sensing system in Listeria
AgrD-dependent quorum sensing affects biofilm formation, invasion, virulence and global gene expression profiles in Listeria monocytogenes. Autoinducer polypeptide binds to surface protein. - picture
What regulates expression of the biofilm phenotype in Listeria?
Quorum sensing!!
Listeria virulence factors
normally motile, but flagella are not produced at 37C (still required for biofilm formation in vitro). associated with the ability of the bacteria to move themselves into, within and between host cells (b/c they are intracellular pathogens)
Listeria adherence and invasion
require internalin; induced by clathrin mediated endocytosis involving InlA which is only expressed at 37C (stimulates its own uptake); InlA and InlB required for crossing placenta
Invasion and Escape
Once inside phagocytic cell - listeriolysin O (LLO) like hemolysin, degrade phagosome as pH decreases; ActA- Promotes the polymerization of actin, a component of the host cell cytoskeleton, on the bacterial surface - works like rocket; expression is regulated! Something about Macrophage or parenchymal cell
How does it cross barriers?
Able to bind and be taken up by many cell types.
How does Listeria infect new cells?
“Bounce” out in small bit of membrane, get phagocytosed, then break out into new cell. Can spread while avoiding Ab response
How does Listeria cause septicemia if it is not generally exposed during transmission b/w cells?
The sheer number of pathogens is huge; and the large amount of nutrients.
Main virulence factors
INLA and B: uptake; LLO: escape from endosome; ActA - polar manner - stimulates actin polymerization
Life cycle review. Consider the relevant virulence factors in each stage (mutlifactorial or -dimensional)
Bind: InlA and B; Endocytosis; Lysis; Actin polymerization; Cell to cell spread. All regulated.
