MICR123 - 5 - E. coli and Shigella

Question 1

What are the physical characteristics of E. coli?

Answer 1

Short, gram-negative, facultative anaerobic microorganism.

Rod-shaped, non-motile (or motile by flagella). Grows optimally at/near 98.6 oF.

Ferments glucose and other CHO to acid (lactic, acetic, formic) and gas (CO2, O2).

Question 2

Describe EnteroPathogenic E. coli(EPEC).

Answer 2

causes severe diarrhea in infants primarily in developing countries.

Question 3

Describe EnteroToxigenic E. coli (ETEC).

Answer 3

causes diarrhea in infants in developing countries.

Also known as Traveler’s Diarrhea.

Can colonize in the small intestines and produce a heat labile/stable enterotoxin causing severe diarrhea.

Question 4

Describe EnteroInvasive E. coli (EIEC).

Answer 4

causes non-bloody diarrhea and dysentery similar to Shigella.

Can colonize in the colon.

Question 5

Describe EnteroAggregative E. coli (EAEC).

Answer 5

causes diarrhea in young children ages 1 - 5 years old.

Symptoms are mild diarrhea without blood.

Question 6

Describe Diffusely Adhering E. coli (DAEC).

Answer 6

causes diarrhea in young children who are older than infants worldwide. (1 month - 2 years of age).

Question 7

Describe EnteroHemorrhagic E. coli (EHEC).

Answer 7

causes bloody diarrhea and produces a cytotoxin called verotoxin (Stxs) similar to Shigella dysenteriae.

Linked to a potentially fatal condition called Hemolytic Uremic Syndrome (HUS).

Question 8

What was the first cause involving E. coli 0157:H7?

Answer 8

The first case involving E. coli 0157:H7 was consuming undercooked hamburgers at a fast-food restaurant.

Question 9

Where and how could there be E. coli waterborne outbreaks?

Answer 9

Waterborne outbreaks of E. coli could be the result of fecal contamination in swimming water, drinking water, well water, and ice.

Question 10

Describe what happened when there was an E. coli outbreak in apple cider and apple juice.

Answer 10

There was an E. coli outbreak in apple juice and apple cider because the apples being used were “dropped apples”.

These dropped apples were the apples that had fallen off the tree which had an increase risk of manure contamination.

Also, the juice was not pasteurized to decrease/eliminate pathogenic microbial population.

Question 11

Describe what happened when there was an E. coli outbreak in hamburger meat.

Answer 11

There was an E. coli outbreak in undercooked hamburger meat because the burgers were not cooked to an appropriate temperature of 155oF. Instead, they were cooked at 140oF.

Question 12

Describe what happened when there was an E. coli outbreak in vegetables.

Answer 12

There was an E. coli outbreak in vegetables because the produce was probably contaminated by fecal matter from wild pigs.

Also, chlorination of vegetables was nut effective in killing E. coli 0157:H7.

Question 13

Why is E. coli 0157:H7 highly toxic?

Answer 13

0157:H7 is highly toxic because only a population less than or equal to 100 bacteria could cause illness.

Question 14

At what point will E. coli 0157:H7 have poor growth?

Answer 14

0157:H7 does not grow well in conditions above 111.2oF.

Also, low acid foods below pH 4.0 will have little to no E. coli.

Question 15

At what temperature and time would be needed to cook certain foods?

Answer 15

• Ground beef (2%)at 135 for 4.1 min,
• ground beef (30%) at 135 for 5.3 min,
• ground beef (2%) at 145 for 0.3 min,
• ground beef (30%) at 145 for 0.5 min,
• pasteurized milk at 162 for 16.2 sec,
• meat in general at 155 for 30 sec.

Question 16

How long would an E. coli infection last?

Answer 16

E. coli infection usually takes 3 - 9 days to show symptoms, and 2 - 9 days to last.

Question 17

What are the symptoms of E. coli infection?

Answer 17

Symptoms of E. coli infection are

• abdominal cramps,
• watery diarrhea,
• grossly blood diarrhea (all blood and no stool), and
• abdominal pain.

Question 18

What is hemolytic uremic syndrome (HUS)?

Answer 18

Hemolytic uremic syndrome (HUS) is an infection in the digestive system that produces toxic substances which destroy red blood cells causing kidney injury.

Question 19

What is the process of E. coli infection?

Answer 19

1. E. coli is ingested.
2. Travels to large intestine, causes inflammation.
3. Adheres to intestinal epithelium.
4. Adhering bacteria destroys villi of intestinal epithelial cells.
5. Creates lesion at destroyed area, causes severe diarrhea.
6. Lesion becomes deep enough to affect blood vells, causes hemorrhage and bloody stools.
7. Toxins enter blood circulation, leads to damaged small blood vessels in kidneys, brain, and other organs.

Question 20

Describe the characteristics of shigella?

Answer 20

Shigella is a

• gram-negative bacilli,
• facultative anaerobe.
• Generally non-motile.
• Population between 10-100 bacteria have caused shigellosis.
• Generally sensitive to heat, but resistant to freezing.

Question 21

What is a facultative anaerobe?

Answer 21

A facultative anaerobe is a microorganism that usually uses oxygen to make ATP.

But when exposed to anaerobic conditions, a facultative anaerobe will start to ferment CHO for energy.

Question 22

What happens during the dysentery stage of shigellosis?

Answer 22

1. Colonizes in the colon and invades the cells in the colon.
2. Dead cells of the intestinal wall sough off. This leads to the presence of blood, pus, and mucus in stools.

Question 23

How long does shigellosis last?

Answer 23

Shigellosis is a self-limiting disease which means that it will last for up to two weeks.

It can be fatal to infants and elderly.