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PID Exams > 18-Shigella / Ecoli > Flashcards

18-Shigella / Ecoli Flashcards

1
Q

Pick one: Shigella are [lactose/non-lactose fermenters], [motile/non-motile] and [capsulate/noncapsulate].

A

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

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2
Q

What is the basis of shigella taxonomy?

A

O-antigen serotyping

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3
Q

What species of shigella is able to make a toxin?

A

Only S. Dysenteriae

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4
Q

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

A

Only human GI tract and transmitted through fecal oral route

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5
Q

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

A

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

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6
Q

What are the two stages of shigellosis?

A

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

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7
Q

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

A

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

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8
Q

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?

A

False. They cause ulceration but rarely cause septicemia

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9
Q

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

A

You would need to culture / isolate the causative the bacteria

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10
Q

How does shigella invade adjacent colonic cells?

A

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

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11
Q

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

A

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

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12
Q

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

A

False, it is contained by the innate immune system

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13
Q

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

A

Through the circulation

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14
Q

What are the 2 major treatments for shigellosis?

A

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

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15
Q

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

A

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

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16
Q

How is the vaccine for shigella administered?

A

There is no vaccine

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17
Q

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

A

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

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18
Q

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

A

O-, H- and K- antigens

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19
Q

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

A

By their biochemical profiles

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20
Q

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

A

True

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21
Q

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

A

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

22
Q

What are the 4 intestinal e.coli pathotypes?

A

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

23
Q

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

A

EIEC

24
Q

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

A

ETEC

25
Q

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

A

Enterotoxin and colonization factors (CFAs)

26
Q

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

A

Heat labile and heat stable

27
Q

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

A

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

28
Q

What is the proposed mechanism of heat stable enterotoxin?

A

Stimulation of guanylate cyclase

29
Q

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

A

Many different antigenic types can mediate attachment to intestines

30
Q

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

A

EPEC, it rarely causes disease in adults

31
Q

Where is EPEC mainly found i.e what is it ingested from?

A

Undercooked meat products

32
Q

What are the 2 EPEC virulence factors?

A

Bundle forming pili (BFP) and locus of enterocyte effacement (LEE)

33
Q

Hemorrhagic (or non-hemorrhagic) colitis and hemolytic uremic syndrome is associated with what e.coli pathotype?

A

EHEC

34
Q

What 2 groups of people are have increased risk of EHEC disease?

A

1) Young children and 2) children who get antibiotics

35
Q

What is the most common e.coli diarrheal disease in developed countries?

A

EHEC

36
Q

What are the 3 virulence factors of EHEC?

A

1) Bundle forming pili (BFP) 2) locus of enterocyte effacement (LEE) 3) shigatoxin (SLT)

37
Q

What is the major means of toxin acquisition by the EHEC strains?

A

Lysogenization (phage integration into the bacterial DNA)

38
Q

How can you differentiate majority of the EHECs from other e.coli pathotypes?

A

Most EHECs don’t ferment sorbitol

39
Q

What e.coli pathotype is associated with UTIs in humans? How it transmitted?

A

UPEC, endogenously transmitted (from same host)

40
Q

As UPECs ascent, what 4 disease / infections can they cause?

A

Urethritis, cystitis, nephritis, pyelonephritis

41
Q

How can UPECs be diagnosed?

A

Greater than 100K CFU/ml in a clean urine catch

42
Q

True or false: There is some level of selection for e.coli that preferentially colonize the GU tract.

A

True

43
Q

What are 4 examples of virulence factors that UPECs have?

A

Adhesins, siderophores, toxins and capsules

44
Q

What are the 2 most common causes of neonatal meningitis?

A

E.coli and Group B strep

45
Q

True or false: Neonatal menigitis is associated with up to 40% mortality and up to 50% serious sequelae in survivors?

A

True

46
Q

What is the specific capsule type found in greater than 75% of ecoli neonatal meningitis? What are its 2 main properties?

A

K1 capsule, it is antiphagocytic and anti-complement(ary)

47
Q

Why is the K1 capsule antiphagocytic?

A

It is essentially sialic acid, therefore not immunogenic

48
Q

What is the distinct toxin associated with 75% of ecoli septic shock w/ hemolysis?

A

RTX toxin

49
Q

Under what conditions will a person be likely to get E.coli septic shock?

A

Underlying compromising condition (liver cirrhosis, following abdominal surgery, cancer patients)

50
Q

How is e.coli septic shock managed? (2 things)

A

Antibiotics and supportive care

PID Exams (17 decks)

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