Listeria Flashcards
How many listeria species are pathogenic
two (of 17)
What are the major serotypes that cause outbreaks of listeria
1/2a, 1/2b and 4b
What lineage of listeria serotypes is the most virulent and why
Lineage 1, they have a tropism for the nervous system and placenta
What is the emergence of Lm associated with
The increased movement of humans, animals and food
In what environment does listeria outcompete other bacteria
In the fridge, in pH as low as 4.4 and salt content as high as 10%
Low temp and high salt
When can Lm survive pasteurization
When it is inside a WBC
How is a major way Lm can survive for years in processing plants
Forming biofilms
Where is Lm often detected
Moist areas, such as floor drains, stagnant water and processing equipment
Lowering temperatures __ Lm growth
Slows
What is a common source of Lm
Raw milk, cold meats
Why are ready to eat meats a good source of Lm contamination
Bc they are heated and then cooled in brine (low temp, high salt) which kills off competing bacteria
What is necroptosis
Programmed cell death process which generates inflammatory signals
What are 3 functions of LLO in Lm
Changes mitochondrial morphology and function
Affects ER by increasing ER stress
Increases permeability of cell bc of pore forming activity
How can Lm spread laterally from cell to cell
By polymerizing actin
What are 3 functions of goblet cells
Secrete mucus to maintain epithelial mucosal barrier
Secrete AMPs, chemokines and cytokines
Deliver luminal antigens to the APCs in the underlying lamina propria and induce adaptive immune responses
What cell does Lm infect in the intestine
Epithelial cells and goblet cells (specialized cell)
What cells does Lm infect to cross the placenta
Trophoblasts
What is the receptor for InlA
E-cadherin
What is the receptor for InlB
Met
How does Lm deal with competitors
It produces listeriolysin S (LLS) that restricts the growth of common commensals
What is a peyer patch
Small masses of lymphatic tissue that are responsible for immune surveillance in the small intestine
Follicles contain B cells surrounded by T cells
How does the immune system protect against Lm in the intestine
Peyer patches (M cells, and T cells may take them up, B cells at the ready) IgA secretion (stops the binding of Lm cells to intestinal cells)
What is the core Lm virulon regulated by
PrfA promoter
Where are the genes controlled by the PrfA promoter in listeria found
On the PAI and on 3 other PrfA regulated loci
How is PrfA itself regulated
It is under its own regulation, which causes a positive feedback loop to regulate the expression of these genes under infectious conditions
