E.coli and Shigella Flashcards

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1
Q

Why is E.coli considered an indicator organism?

A

It is found in the guts of humans and cows. It’s presence in the water represents possible fecal contamination.

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2
Q

What is the optimum growth temperature for E.coli? Why is it this particular temperature?

A

37 C. This is the temperature of the gut from humans and other mammals

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3
Q

What is the infectious dose of <i>E. coli<i> O157:H7?</i></i>

A

1-10 cells. Crazy low!

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4
Q

What are the 2 antigens targeted for E. coli serotyping? Where can these antigens be found?

A

See slide 5 for discussion of O- and H- antigens

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5
Q

What is an “adulterant” in food? Is E. coli O157:H7 one of these?

A

An adulterant is a zero tolerance organism (no amount is allowed in the food). Yes- it is!

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6
Q

What species of Shigella produces shiga toxin?

A

S. dysentery.

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7
Q

What is the reservoir of Shigella?

A

Humans

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8
Q

What are “pathotypes” of E. coli, and can you name a few?

A

This word refers to the different types of E. coli that exist, that can cause different types of diseases. See slide 4 for a few examples

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9
Q

What are some typical food sources of E. coli O157:H7?

A

Ground beef is still tops (>50% of outbreaks), however fresh produce is rapidly on the rise (currently about 25% of outbreaks).

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10
Q

What is the purpose of the carcass washer for minimizing E. coli O157:H7?

A

See slide 9; this is an antimicrobial wash (hot water, sometimes an organic acid) for killing E. coli that is on the hide of the animals

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11
Q

What were some of the new policy changes that came out of the E. coli apple cider outbreak we discussed in class?

A

See slide 12; recognition that cider could be a vehicle for E. coli, as it was previously assumed that this organism couldn’t survive in such acidic environments.

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12
Q

What are the “Big Six” E. coli?

A

The six serogroups of Shiga toxin-producing E. coli other than O157 that are common human disease isolates; serogroups O26, O45, O103, O111, O121, O145

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13
Q

The reservoir of the Big Six E. coli is….

A

Cattle, and other ruminants (same as O157:H7). However as discussed in class, they seem to cause problems in a wider variety of foods than O157:H7. See slide 13.

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14
Q

The genus “Shigella” refers to organisms that are genetically identical to …..

A

Escherichia coli

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15
Q

Two differences (one phenotypic, and the other related to the reservoir) between Shigella and most other E. coli is:

A

See slide 17

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