18-Shigella / Ecoli Flashcards Preview

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Flashcards in 18-Shigella / Ecoli Deck (50)
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Pick one: Shigella are [lactose/non-lactose fermenters], [motile/non-motile] and [capsulate/noncapsulate].

Shigella is non-lactose fermenting, non motile and non-capsulate


What is the basis of shigella taxonomy?

O-antigen serotyping


What species of shigella is able to make a toxin?

Only S. Dysenteriae


Where is the only place Shigella is found? How is it transmitted?

Only human GI tract and transmitted through fecal oral route


True or false, shigella disease requires ingestion of a lot of bacterial particles because they are killed by the stomach acidity?

False, only 1-10 particles needed because they are particularly resistant to stomach acid


What are the two stages of shigellosis?

Stage 1 is in the small intestines while stage 2 is invasion of large intestines


True or false: Frequent stools, no pus and no blood, abdominal cramps, malaise, fatigue, anorexia, diarrhea and vomiting are ALL associated with shigellosis.

False. There is significant pus and blood. All other descriptors are correct


Shigella causes colonic ulceration. This is the route that they use to invade and cause cause their frequently occuring septicemia.Is that true or false?

False. They cause ulceration but rarely cause septicemia


In a laboratory setting, how would you distinguish salmonellosis from shigellosis?

You would need to culture / isolate the causative the bacteria


How does shigella invade adjacent colonic cells?

Lateral movement THROUGH the adjacent cells (i.e. pushes through into adjacent cell)


Again, what is the only sub type of shigella that makes toxin? What are the two main organ systems affected?

S. dysenteriae is the only subtype that makes shiga toxin. The toxin is neurotoxic and nephrotoxic


True or false: The major means of containing shigella to the gut is by antibody (IgA) in colonic mucosa?

False, it is contained by the innate immune system


Shiga toxin is nephrotoxic. How does it reach the kidneys to exert its toxic effects?

Through the circulation


What are the 2 major treatments for shigellosis?

Rehydration and antibiotics (the latter shortens the duration of disease by limiting shedding)


What are the 3 best practices highlighted in the notes for preventing spread of disease?

1) Good waste water treatment facilities, 2) handwashing and 3) healthy food handlers


How is the vaccine for shigella administered?

There is no vaccine


How would you distinguish e.coli from shigella on a McConkey plate? Why?

E.coli would be pink (vs. pale shigella) because of lactose fermentation


What are the 3 major antigens use to divide e.coli into serotypes?

O-, H- and K- antigens


What is the major means of distinguishing e.coli from other enterics?

By their biochemical profiles


True or false: E.coli are part of normal GI flora and are required for health



What are 4 extra-intestinal diseases associated with e.coli?

1) UTIs, 2) GI infections 3) Septicemia 4)neonatal menigitis


What are the 4 intestinal e.coli pathotypes?

Enteroinvasive (EIEC)
Enterotoxigenic (ETEC)
Enteropathogenic (EPEC)
Enterohemarrhagic (EHEC)


What e.coli pathotype produces disease essentially identical to shigellosis?



Traveler's diarrhea (abrupt onset but not invasive) that is endemic in developing countries is what e.coli pathotype?



What are the 2 major virulence factors of enterotoxigenic e.coli?

Enterotoxin and colonization factors (CFAs)


What are the 2 possible subtypes of enterotoxin produced by ETEC?

Heat labile and heat stable


The heat labile toxin made by ETEC acts in a similar manner to cholera toxin. Why is disease less severe?

ETEC secrete toxin into periplasm, trapping it, therefore the toxin load that "gets to the host" is lower than in cholera


What is the proposed mechanism of heat stable enterotoxin?

Stimulation of guanylate cyclase


Why is it hard to make a vaccine to colonization factors of e.coli?

Many different antigenic types can mediate attachment to intestines


What is the e.coli pathotype that is associated with disease in young children living in developed countries? Does this cause disease in adults?

EPEC, it rarely causes disease in adults