Viral & Bacterial Causes of Gastroenteritis

Question 1

This bacteria is halophilic and grows at low temperatures. It is the most severe form of enteritis and may harm a fetus. How is it spread?

Answer 1

Listeria - food-borne via cheese, ice cream, lunch meats

Question 2

What is the leading cause of sporadic viral gastroenteritis and outbreaks?

Answer 2

Norovirus

Question 3

What bacteria is responsible for causing enteric fever?

Answer 3

Salmonella Typhi

Question 4

What agar may be used to differentiate Shigella & Salmonella?

Answer 4

Hektoen agar - Salmonella produces H2S, while Shigella does not

Question 5

While this pathogen is not the leading cause of bacterial gastroenteritis, it does cause the most hospitalizations.

Answer 5

Listeria

Question 6

With enteric fever, bacteria survive and replicate within macrophages and cause bacteremia. What organ is chronically infected?

Answer 6

Gallbladder

Question 7

True/False. E. coli does not ferment lactose.

Answer 7

False. E. coli ferments lactose, but Shigella does not.

Question 8

What is the mechanism of the cholera toxin?

Answer 8

AB toxin - increases cAMP, stimulates PKA, Cl- influx, watery diarrhea

Question 9

Infection with this bacteria presents with “rice-water stool.”

Answer 9

Vibrio cholerae

Question 10

What is the most common type of Shigella seen in the USA?

Answer 10

Shigella sonnei

Question 11

What complications are associated with C. jejuni infection?

Answer 11

Guillain-Bare Syndrome, reactive arthritis

Question 12

This bacteria is responsible for the most cases of foodborne gastroenteritis in the USA.

Answer 12

Salmonella, STEC, Listeria

Question 13

Infection with this bacteria is associated with coastal water contaminated with sewage, raw oysters, and shellfish.

Answer 13

Vibrio cholerae & parahaemolyticus

Question 15

What is the most severe complication of STEC?

Answer 15

Hemolytic uremic syndrome (renal failure, thrombocytopenia, hemolytic anemia)

Question 16

These subtypes of V. cholerae cause clinical cholera.

Answer 16

O1 & O139 - all other subtypes cause vibriosis

Question 17

What agar may be used to differentiate STEC?

Answer 17

Sorbitol MacConkey Agar - STEC does not ferment sorbitol

Question 18

This type of Shigella produces a Shiga-like toxin.

Answer 18

Shigella dysenteriae

Question 19

This gastroenteritis-causing bacteria has bipolar staining, grows at colder temperatures, and may mimic appendicitis.

Answer 19

Yersinia enterocoltica & pseudotuberculosis

Question 20

STEC is most associated with what sources?

Answer 20

Livestock and petting zoos, contaminated beef

Question 21

This bacterial cause of gastroenteritis is most associated with nursing homes, daycare, etc.

Answer 21

Shigella spp.

Question 22

What virulence factor is most responsible for STEC infection?

Answer 22

Intimin - bacterial adhesion molecule

Question 23

What virulence factors are associated with Listeria?

Answer 23

Listeriolysin O - enables escape from phagolysosomes

Act A - rearrangement of actin for motility

Question 24

True/False. Doxycycline should be used to treat STEC.

Answer 24

False - this can cause overwhelming toxin release. The infection must run its course.

Question 25

This bacteria does not ferment lactose or produce H2S.

Answer 25

Shigella spp.

Question 26

This dsRNA is most common to cause gastroenteritis in children <5.

Answer 26

Rotavirus

Question 27

What subtype of E. coli produces the Shiga-like toxin?

Answer 27

O157:H7 (STEC)

Question 28

What are the characteristics of norovirus?

Answer 28

+ssRNA, naked, icosahedral

Question 29

Bacillus cereus products both a heat-stable and labile enterotoxin. How does the presentation of infection with these toxins differ?

Answer 29

Heat-stable - emetic form, rice, vomiting, intoxication

Heat-labile - diarrheal form, meats, diarrhea, infection

Question 30

What Rotavirus proteins are targets for vaccines?

Answer 30

VP4 & VP7

Question 31

H. pylori persists within the stomach and is associated with peptic ulcers and adenocarcinoma. What are its characteristics?

Answer 31

Spiral G- rod, corkscrew motility, microaerophilic, urease +

Question 32

This E. coli subtype is the leading cause of traveler’s diarrhea.

Answer 32

Enterotoxigenic E. Coli (ETEC)

Question 33

This bacteria is microaerophilic and capnophilic and spreads via undercooked chicken.

Answer 33

C. jejuni

Question 34

Staph aureus can cause gastroenteritis via enterotoxin A, causing vomiting. What foods are associated with intoxication?

Answer 34

Processed meats, dairy products, mayonnaise-based salads

Question 35

What Rotavirus protein functions as an enterotoxin?

Answer 35

NSP4

Question 36

Salmonella gastroenteritis is most associated with what causes?

Answer 36

Undercooked chicken, raw eggs, reptiles (small turtles)

Question 37

This bacteria is a major cause of diarrhea in hospitals and is associated with antibiotic-acquired gastroenteritis.

Answer 37

C. difficile

Question 38

This bacteria is a leading cause of inflammatory diarrhea in the USA.

Answer 38

C. jejuni

Question 39

Vomiting as a symptom of gastroenteritis generally indicates what type of infection?

Answer 39

Viral infection - except Staph aureus & Bacillus cereus, which produce enterotoxins that induce vomting