Lecture 20 Salmonella and Yersinia . Flashcards
What are the common themes?
- facultative anaerobic rods
- use enteritis and systemic diseases
- type III secretion
- Both require adherence to intestinal epithelial cells, particularly the M-cells of Peyer s Patches to gain access to extra-intestinal sites.
- interact with macrophages
What are the subgroups of Salmonella enterica?
Enterica/cholerasuis salamae arizonae diarizonae houtenae indica
Which salmonella strain are found in humans and mammals?
enterica
Salmonella enterica is prominently found in?
reptiles and the environment .
Salmonella is mostly found in what type of hosts?
warm blooded animals
What are the characteristics of salmonella?
- gram negative bacilli with peritrichous flagella
- non-spore forming, non-lactose fermentation (except s. Arizona
- H2S formation
- SS agar, hektoen, XLT, McConkey
- serology based on H, O, and flagella
- capsule, Vi antigen
What are the sx of non-typhoidal salmonella infections?
-fever, abd cramps, diarrhea (possibly bloody), occasionally can establish localized infection (septic arthritis) or progress to sepsis.
How is salmonella transmitted?
ingested of contaminated food, water, or animal contact
What are the prevalent serotypes of salmonella?
-S typhimurium, S enteritidis, S. Newport.
What is the pathogenesis of salmonella?
- oral ingestion
2.infectious dose depending on food: lower if gastric acidity is buffered - bacteria travel to the distal ileum-uptake is mediated by M-cells and patrolling CD18+ cells
- invasion of theses cells mediated by SPI1
5.ruffing of epithelial cell facilitates uptake of salmonella - once across intestinal epithelial cell, salmonella encounters phagocytic cells in lamin propia
Survival in phagocytic cell depends on SPI2 gene.
What are key functions for Salmonella Pathogenicity Islands (SPI1)?
- ability to invade host epithelial cells
- virulence of Salmonella by the oral route
- required to survive and replicate in host macrophages
What does SipA do?
actin filaments that cause membrane ruffling
What does sop D/B do?
promote chloride and fluid secretion
How does SPI2 protect salmonella from phagosome?
- products prevent the accumulation of toxic oxidative products by preventing NADPH oxidase complex from forming on phago
- effector proteins are exported into the cytoplasm
- prevent maturation of phago
What is typhoid fever characterized by?
- fever, headache, constipation, malaise, chills, and myalgia. Diarrhea uncommon and vomiting is not usually severe.
- confusion, delirium, intestinal perforation, and death in sever cases
How is typhoid passed on?
water or food. Large epidemics due to fecal contamination
Are there vaccines for Typhoid?
Ty21a live oral
Vi-antigen injectable form
What are the characteristics of Salmonella Typhi?
- produce Vi-antigen by SPI7
- Vi antigen is often described as being anti-phagocytic
- Vi antigen involved in shielding typhi from stimulating TLR5 and TLR4
- over 200 pseudogenes
How do NTS and S typhi interact differently with the immune system?
S Typhi indifferent to components of innate immunity that play a crucial role in resistance to NTS
What is Salmonella-mediated enteritis specifically caused by?
toxin or enterotoxin
What is needed to induce neutrophil migration and inflammation of Salmonella-mediated enteritis?
-Products of SPI1, induced tissue damage is cause of fluid formation
What are the characteristics of Yersinia?
11 species
Y. enterocolitica and Y.pseudotuberculosis are human pathogens, but found in animals too
Swine major reservoir but does not succumb to infection
What is the pathogenicity of Yersinia enterocolitica?
- ingestion of contaminated food
- adhere to and invade M-cells, encounter macrophages
- growth takes place in lymph nodes, spleen and liver
- Usually does not cause septicemia. Usually immuno compromised people who are iron-overloaded or being treated with deferoxamine
What are the important virulence factors of Yersinia?
- invasin
- yops (EOTHP)
- yersiniabactin
What is invasin?
protein expressed on the surface of the bacterium that facilitates uptake by host cell
What is yops?
group of proteins produced on virulence plasmids and pathogenicity islands that are unique to Yersinia. secreted by type III secretion system
What is Yersiniabactin?
siderophore that is able to bind and transport of extracellular iron onto the cell.
What doe Yop E do?
Depolymerizes actin
What does Yop O do?
phosphorylates host proteins-disrupts cell signalling
What does Yop T do?
depolymerizes actin
What does YopH do?
dephosphorylation of signal transduction proteins
What does Yop P do?
inhibits macrophage apoptosis and prevent TNF alpha release
