Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

59 Cards in this Set

  • Front
  • Back
What is gastroenteritis?
What is its timeframe for onset?
-An intestinal infection caused by proliferation of bacteria.
-12 hours to days after ingestion
What makes food poisoning different from gastroenteritis?
The GI symptoms appear within a few hours of eating.
What is Diarrhea?
>300 g of stool daily with increased liquidity and frequency.
What is Secretory diarrhea?
Water and ion loss but no damage
What is Malabsortive diarrhea?
Diarrhea in which there is damage to mucosal cells that impairs water uptake
What is Dysenterey?
Multiple, bloody, mucoid stools
What are 6 features of ALL enterobacteriaceae?
1. Gram neg rods
2. Non spore forming
3. Facultatively anaerobic
4. Ferment glucose
5. Reduce nitrates
6. Oxidase neg
What is the motility of enterobacteriaceae?
All are MOTILE except
-K. pneumoniae
-one salmonella
What is the flagella of Salmonella like?
How is Salmonella differentiated on MAC?
It is a lactose nonfermentor
What Salmonella species are highly adapted to humans?
-S. typhi
-S. paratyphi
-S. sendai
What disease is caused by S. typhi?
Typhoid fever
How is typhoid fever different from typhus?
It has enlarged Peyers patches and mesenteric lymph nodes.
What causes typhus?
Rickettsia rickettsii
What are the 2 species of Salmonella classification?
S. enterica
S. bongori
How many subspecies of S. enteritica are there? How are they differentiated?
7 - ID'd by biochemical characteristics and serotyping
What is Salmonella Typhi really?
S. enterica, serotype group I
What is the most frequent human isolate of Salmonella?
S. typhimurium
What are the 2 clinical syndromes that S. typhimurium causes?
1. Gastroenteritis
2. Systemic infection
What is the mode of Salmonella transmission?
Ingestion of contaminated food or water
How are Salmonella bacteria able to colonize the gut?
They survive the stomach's acidity
What cells do Salmonella bacteria target to invade GALT/peyers patches?
M cells
What are the steps in Salmonella invasion of the gut?
1. Salmonella ruffles Mcell membrane and gets taken up
2. Infected M cells die and leave a hole in the GI epithelium
3. bacteria move down into lymphocytes
What is the virulence factor that Salmonella bacteria use to get into cells?
Type III secretion system
What did the type III secretion system evolve from?
Motility mechanisms
How many type III secretion pathways does each salmonella bug use? What are they called?
What is SPI1 required for?
-Salmonella entry into cells
-Translocation of effectors across the plasma membrane
What is the effect of the translocated effectors that are stimulated by SPI1?
-Actin bundles and polymerizes to inhibit host phagocytosis pathways
What does SPI2 do?
Allows the bacterium to survive intracellularly by maintaining SVC integrity and preventing lysosomal fusion with it.
So the two diseases caused by salmonella infections are:
-Nontyphoidal gastroenteritis
-Typhoid fever
How does typhoid fever develop?
By entry of bacteria into M cells and proliferation in lymphoid follicles.
How can typhoid fever be prevented?
By vaccinating
What bacterium causes Dysentery?
What is the special feature of Shigella?
How is Shigella transmitted?
Fecal to oral in contaminated food and water
What are the four species of Shigella?
S. dysenteriae
S. boydii
S. flexneri
S. sonnei
In what patients do 70% of all Shigellosis cases occur?
What is the illness caused by Shigella indistinguishable from?
Illness caused by invasive strains of E. coli
Why do E. coli and Shigella cause the same illness?
They have the same virulence plasmid
What does the virulence plasmid of E.coli and Shigella encode?
a Type III secretory system
What are the 5 effectors associated with the virulence of Shigella?
What is IPA?
Invasion protein antigens
What do humans do in response to IPAs?
Make antibodies to them
What is the first step in Shigella invasion of an intestinal epithelial cell?
IpaB-C complex binds an integrin on the epithelial cell, inducing a signalling cascade for ACTIN POLYMERIZATION (IpaA)
What happens after initial binding of shigella to the cell?
The membrane ruffles via actin polymerization, then it depolymerizes to form a vacuole containing Shigella.
Does Shigella like being in a vacuole? Why?
No - it has no SPY2 analog to maintain the vacuole and prevent lysosomal fusion.
What happens to shigella once it is free within an enterocyte's cytoplasm?
It forms its own motility mechanism by polymerizing ACTIN
Why does Shigella form an actin Comet Tail?
To propel itself into neighboring enterocytes
So what direction do Salmonella bacteria invade the intestine?
Vertically - down into lymphatic tissue
What direction do Shigella bacteria invade the intestine?
Laterally - into neighboring cells
In addition to Invasiveness, how does shigella damage the host?
Via Shiga toxin - Stx
What type of toxin is the shiga toxin?
An AB5 toxin
What is the enzyme activity of the A subunit of shigatoxin?
What is the receptor for B?
RNA N-glycosidase that cleaves Adnine from the 28s ribosome and inhibits host protein synthesis.
B targets Gb3 terminal galactose residues.
What is achieved by shigatoxin?
It stops host protein synthesis
What are the 3 names for shigatoxin?
-Shigalike toxins
What is the range of pathology caused by the shigatoxins?
-Mild and watery stools
-Severe bloody diarrhea
HUS (e.coli o157H7)
Which strains of shigatoxin are most likely to cause HUS? Why?
Stx2 in E. coli - because it is encoded on a phage
How are Salmonella and Shigella similar?
Both have Acid tolerance
Which bacterium causes more host damage? Why?
Shigella - because it results in mucosal abscesses.