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Infectious Disease Exam 1 > Enteric Bacteria I and II > Flashcards

Enteric Bacteria I and II Flashcards

1
Q

Diarrheal diseases are a much bigger problem in __________ countries.

A

poor

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2
Q

Which bacteria causes the most diarrheal deaths worldwide?

A 
Shigella (730,000) 
Salmonella typhi (600,000) 
Escherichia coli (380,000) 
Cholera vibrio (120,000)

Note: most deaths are due to viral diarrhea [rotavirus (800,000)]

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3
Q

What is the main route of enteric bacterial infection?

A

Fecal-oral (often from contaminated poultry, beef, eggs, milk, and vegetables)

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4
Q

The ability to resist acid determines ______________.

A

infectivity; that is, the more acid-resistant a bacterium is, the fewer bacteria that are needed to cause an infection (so Shigella needs as few as 10 organisms to cause infection)

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5
Q

Which enteric bacteria are acid-labile?

A

Salmonella and Vibrio (think of the lemon by the salmon and the lemon on the oyster tray in the cholera sketch)

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6
Q

Vibrio cholera grows well on ______________.

A

alkaline media

Think of the “BASE camp” written on the map in the Colonel Cholera sketch.

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7
Q

In the bacterial nomenclature of O’s and H’s, what do each mean?

A

O: lipopolysaccharide (which has two O’s; also, lipopolysaccharide is the source of endOtoxin)
H: flagellum (“fla-HELL-um”)

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8
Q

The heat-stable toxin of E. coli raises intracellular ______________.

A

cGMP (eL Agua de San Gabriel: Labile raises cAMP and Stabile raises cGMP)

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9
Q

Bacteriophage conversion can produce ______________ in a bacterium.

A

toxin expression

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10
Q

________________ are remnants of foreign DNA that allow bacteria to infect hosts.

A

Pathogenicity islands

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11
Q

_____________ allow E. coli to infect hosts and demonstrate tropism.

A

Pili (Sketchy shows this by the ponytails of the girl sitting at the E. Cola diner bar)

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12
Q

What is the difference between bloody diarrhea from dysentery and EHEC?

A

Dysentery makes smaller volume bloody stools

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13
Q

What external feature of Vibrio cholera allows it to infect humans?

A

It has fimbriae (toxin co-regulated pilus – TCP) and a flagellum.

(Think of the ROPE tying the cholera raft to the bank of the river in the Colonel Cholera sketch.)

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14
Q

Which enteric bacteria commonly infects shellfish?

A

Vibrio cholera (like the oysters on Colonel Cholera’s plate)

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15
Q

_________________ allowed cholera to become toxic.

A

The pili allowed the bacteriophage to dock and infect the cells with the toxin-containing DNA.

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16
Q

Describe the layout and function of cholera toxin.

A

It has two subunits –A and B. The B unit binds the cell and the A unit acts to increase cAMP. First, though, the dimer must enter the endoplasmic reticulum.

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17
Q

Eschericia coli grows ___________ on EMB agar.

A

green (like the green coasters in the E. Cola sketch)

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18
Q

Which virulence factor from E. coli causes secretory diarrhea?

A

Both the heat-labile and heat-stable toxins contribute to the development of secretory diarrhea.

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19
Q

Adherence factor helps ____________ colonize the intestine.

A

E. coli

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20
Q

Which of E. coli’s toxins is more similar to cholera toxin?

A

The heat-labile toxin is more similar because they both raise cAMP.

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21
Q

The bacteria that forms pedestals on microvilli has what unique virulence factor (for its species)?

A

Type III secretion system

(This describes enteropathogenic Eschericia coli –EPEC –P for EPEC and P for Pedestal; it is a common cause of watery diarrhea.)

22
Q

True or false: EHEC ferments sorbitol.

A

False. EHEC is non-sorbitol fermenting.

23
Q

How does the EHEC toxin work?

A

It inhibits the 60S ribosomal subunit.

(You need to remember two Sketchy mnemonics: the boy in the EHEC sketch is holding the She-Gorilla; and in the Shigella sketch, the gorilla is being timed with the 60-Second hourglass next to the actin cannon.)

24
Q

True or false: EHEC starts with mucus and blood in the stool.

A

False. Typically, EHEC starts with watery diarrhea.

25
Q

When does EHEC typically present (after consumption)?

A

2-3 days after consumption

26
Q

Which Shigella strain is the most severe?

A

Shigella dysenteriae (group A; this is the only kind that can make Shiga toxin)

27
Q

What allows Shigella strains to become toxic?

A

Type III secretion systems

In the Sketchy scene, the young ringmaster is holding a turkey baster!

28
Q

Shigella invades __________ cells.

A

M (like the M on the She-Gorilla cannon)

29
Q

What distinguishes M cells from other enterocytes?

A

They do not have microvilli (M cells are Minus Microvilli)

30
Q

Why does Shigella cause bleeding?

A

It secretes IL-8 which attracts neutrophils. The neutrophil invasion secretes damaging proteins and chemicals.

(Think of neutrophils with IL-8 because neutrophils are polymorphonuclear and the number 8 is a bi-lobed symbol.)

31
Q

Many people write about Salmonella typhi as if it is a unique species, but actually _________________.

A

it is a serovar of Salmonella enterica (as is S. enteriditis)

32
Q

What diseases are commonly caused by non-typhoidal S. enteriditis?

A

In healthy people, S. enteriditis commonly causes watery, self-limited diarrhea. In those with HIV, however, Salmonella can disseminate.

33
Q

What is the incubation period for Salmonella typhii?

A

1-3 weeks

34
Q

How do people shed typhoid without developing symptoms?

A

S. typhii colonizes the gallbladder and sheds organisms into the stool, but it does not invade.

35
Q

Salmonella survives by _____________.

A

triggering its own entry into macrophages

36
Q

The ______________ of Salmonella allows it to evade phagocytic cells.

A

capsule (remember the video of the neutrophil trying to get the Salmonella without the capsule)

37
Q

Campylobacter is often said to be ___________-shaped.

A

gullwing (honestly, to me, it looks like a mustache)

Think of the mustache on the camper in the Skethcy scene.

38
Q

Campylobacter outbreaks are often associated with _________________.

A

raw milk, uncooked poultry (individual cases), and contaminated water

39
Q

Sketchy left out a couple important features of Campylobacter: _______________.

A

it has flagella and it colonizes the distal ileum

40
Q

Describe Helicobacter.

A 
Gram-negative (red helicopter)
Motile (moving helicopter rotors) 
Urease-positive (pilot cleaning his windshield with ammonia)
Multi-flagellated 
Oxidase-positive (pilot's ring) 
Curved (pilot's mustache)
41
Q

Campylobacter is catalase-_____________.

A

positive

Sketchy notably omitted this, but I saw it in lab and online!

42
Q

What is the K antigen?

A

The capsule (“kapsule”)

Remember the encapsulated Kake in the E. coli sketch.

43
Q

How does cholera toxin activate Gs?

A

By ribosylating it

Imagine a bow on Colonel Cholera.

44
Q

What diarrhea is typical of EPEC?

A

Persistent watery

ePec = Persistent diarrhea

45
Q

True or false: E. coli cannot survive in anaerobic conditions.

A

False. E. coli is a facultative anaerobe.

46
Q

Shigella is a human-adapted organism, while ____________ is not and passes from species to species.

A

Salmonella

47
Q

Like Shigella, Salmonella also _______________.

A

invades M cells first and then invades macrophages

Think of the M on the cages above the fowl.

48
Q

_______________ is the most common cause of bacterial gastroenteritis in the western world.

A

Campylobacter

49
Q

Campylobacter can cause _____________ in individuals with HLA-B27.

A

reactive arthritis

50
Q

Severe ETEC or V. cholerae can be treated with ________________.

A

fluoroquinolones

Infectious Disease Exam 1 (17 decks)

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