9. Listeria Flashcards
Is Listeriosis a notifiable disease?
Yes
Why is a mouse a poor model for Listeria?
Has different E - cadherin
Examples of invasive pathogens
Shigella, Listeria monocytogenes
What disease does Shigella cause?
Bacillary dysentery - inflammatory colitis resulting in bloody diarrhoea
Features of Listeria monocytogenes
Gram positive bacteria (thick peptidoglycan layer)
Rod-shaped
Motile (at 25℃, not at 37℃)
Psychrotrophic (can replicate in refrigerated food)
Food borne invasive pathogen
How does Listeria monocytogenes gain access to underlying immune cells?
It has to invade gut epithelial cells to help it spread systemically throughout the body where it can colonise the liver & spleen and cause systemic disease - often fatal
What disease does Listeria monocytogenes cause?
Listeriosis
Symptoms of listeriosis?
Symptoms range from mild flu-like illness to infections of CNS (meningitis, encephalitis) and ultimately, septicaemia
Can Listeria cross the placental barrier?
Yes
What is the most common bacterial killer of foodborne origin?
Listeria
What is the fatality rate associated with Listeriosis?
20-40%
Who does Listeria mainly affect?
YOPIs = young, old, pregnant, immunocompromised
What are pregnant women advised not to eat (due to Listeria risk)?
Unpasteurised dairy
What was the first outbreak to link listeriosis with food?
Coleslaw Outbreak in Canada (1981)
infected sheep → fertiliser → cabbage → coleslaw → humans
Does L. monocytogenes have a high or low infectious dose in susceptible people?
Low
How do L. monocytogenes enter the body?
Through the gastrointestinal tract
Does L. monocytogenes survive the low pH of the stomach?
Yes, it is also quite bile-resistant
Describe the pathogenesis of Listeriosis
- Adherence of bacteria to epithelial cells
- Mediated by Internalin A & B
- Internalin A binds to E-cadherin (InlA most important in terms of getting across gut barrier) → signalling cascade within host epithelial cell
- Must colonise gut to invade
- InlB binds Met (more important for ubiquitous spread of bacteria to liver & spleen)
At what stage of listeriosis pathogenesis is Internalin A important?
Important early on as Listeria gains hold
InlA receptor only found in certain places i.e. intestines
At what stage of listeriosis pathogenesis is Internalin B important?
Important in systemic spread of disease in later stages
InlB receptor is ubiquitous
Human primate model of listeriosis?
Good uptake, good spread, poor model (unethical & expensive)
Mouse model of listeriosis?
Poor uptake (InlA doesn’t bind well to mouse E-cadherin), good spread (InlB binds well to mouse Met protein), poor model overall because you have to give very high doses of Listeria to a mouse in order to establish an infection (poor oral infection)
Guinea pig/ rabbit model of listeriosis?
Good uptake (adherence), poor spread, poor model (poor systemic infection)
Gerbil model of listeriosis?
Good uptake, good spread, good model? (has never been tested)