E.coli and Shigella Flashcards Preview

Food Microbiology > E.coli and Shigella > Flashcards

Flashcards in E.coli and Shigella Deck (15):

Why is E.coli considered an indicator organism?

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


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

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


What is the infectious dose of E. coli O157:H7?

1-10 cells. Crazy low!


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

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


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

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


What species of Shigella produces shiga toxin?

S. dysentery.


What is the reservoir of Shigella?



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

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


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

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


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

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


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

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.


What are the "Big Six" E. coli?

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


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

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.


The genus "Shigella" refers to organisms that are genetically identical to .....

Escherichia coli


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

See slide 17