Infectious Diarrhea

Question 1

What is the #1 cause of acute viral gastroenteritis?

Answer 1

Norovirus

Question 2

How is acute viral gastroenteritis caused by norovirus treated?

Answer 2

Supportive care

Question 3

What is a long term post-infectious sequelae of norovirus infection?

Answer 3

post-viral gastroparesis

Question 4

Can norovirus cause chronic infection?

Answer 4

Apparently yes, looks like asymptomatic carriers can act as a reservoir

But usually, symptoms rapidly controlled within 48-72 hours

Question 5

What is the most common cause of bacterial foodborne illness in the U.S>

Answer 5

Salmonella (S. enteriditis) a nontyphoidal infection

Question 6

What are the two distinct diseases of salmonella?

Answer 6

Outside of U.S. = typhoid fever

In U.S. = nontyphoidal infections

Question 7

How are nontyphoidal salmonella infections transmitted?

Answer 7

Food transmission (eggs, milk, meat, etc.)

Pet transmission (lizards, turtles, etc.)

Question 8

What is the characteristic clinical presentation of typhoid fever?

Answer 8

Week 1: Stepwise fever and bradycardia

Week 2: Rose spots on abdomen + pain

Week 3: GI bleeding, perforation

Constipation

Question 9

Do you treat salmonella with antibiotics?

Answer 9

Typhoid fever high mortality without antibiotics, must treat travelers

Non-typhoidal disease, no advantage to giving antibiotics because it is typically self limited (unless patient is very ill)

Question 10

Can salmonella cause chronic infection?

Answer 10

In typhoid fever, it may persist in gallstones

In non-typhoidal disease not likely

Question 11

What is the second most common food-borne bacterial infection in the U.S.

Answer 11

Campylobacter

Question 12

What IBD can campylobacter mimic?

Answer 12

Crohn’s Disease since it starts in ileum/jejunum and comes to colon

Question 13

What are acute complications of campylobacter infection?

Answer 13

Pseudo-appendicitis in kids

Question 14

What are long term complications of campylobacter infection?

Answer 14

Reactive arthritis

Guillain-Barre polyneuropathy

Question 15

What is the most common cause of bloody diarrhea worldwide?

Answer 15

Shigella

Question 16

What is the most important virulence factor of Shigella and why is it dangerous?

Answer 16

Shiga toxin –> can lead to HUS

Question 17

What is an E.Coli strain that also causes bloody diarrhea and HUS (very much like Shigella); what serotype is most recognized in U.S.

Answer 17

EHEC (Enterohemorrhagic E. Coli) aka O157:H7

Also produces shiga toxin as a virulence factor

Question 18

Are antibiotics used to treat EHEC infection?

Answer 18

NO. Antibiotics are contraindicated because there is higher risk of HUS with antibiotic use

Question 19

What triad of symptoms defines HUS

Answer 19

Acute renal failure

Microangiopathic hemolytic anemia

Thromboycytopenia

Question 20

How are ETEC and EPEC similar?

Answer 20

Both cause watery, non-bloody diarrhea in kinds in developing countries

Question 21

How does cholera toxin work to cause watery diarrhea?

Answer 21

B subunits bind to ganglioside receptor (GM1) on apical surface

A subunit enters and is cleaved into A1 and A1

A1 moves to basolateral membrane and irreversibly activates a g protein

Causes an increase in cAMP and increased Cl secretion (inhibition of NaCL transport)

Water follows ion efflux out of cell

Question 22

What are clinical manifestations of cholera?

Answer 22

Painless, rice-water stool with fishy smell = up to 1 liter/hour

Question 23

FACT: C. Difficile forms spores and is highly infectious

Answer 23

WASH HANDS WITH SOAP and WATER

Question 24

What are the two exotoxins required for pathogenicity in C. Diff and which is more potent?

Answer 24

Toxin A (enterotoxin) and Toxin B (cytotoxin)

B is more potent

Question 25

What are main clinical findings of C. Diff?

Answer 25

Watery diarrhea, abdominal cramping, fever, pseudomembranous colitis --> toxic megacolon

Question 26

What is treatment for C. Diff

Answer 26

Metronidazole Oral Vancomycin Fecal Microbial Transplant (FMT)

Question 27

How is Clostridium perfringens transmitted?

Answer 27

Food-borne --> germinates in contaminated meats

Question 28

What is the enterotoxin of Clostridium perfringens?

Answer 28

Enteritis necroticans (pigbel)

Question 29

What are risk factors for contracting Clostridium perfringens?

Answer 29

Consumption of pig guts (chitterlings) Sweet potatoes Antipsychotic drugs that decrease GI motility

Question 30

What do you need to know about bacteroides fragilis?

Answer 30

It has a similar presentation to C. Diff

Question 31

What are the two bacteria that are transmitted through pork (chitterlings)

Answer 31

Yersinia | Clostridium perfringens

Question 32

What are the two bacteria that can present as pseudoappendicitis?

Answer 32

Campylobacter and Yersinia

Question 33

What else comprises usual clinical presentation of Yersinia infection in children?

Answer 33

``` Dysentery Fever Pharyngitis NO abdominal pain Pseudoappendicits ```

Question 34

Which bacteria most often infects pregnant women?

Answer 34

Listeria monocytogenes | primarily affects elderly, immunosuppressed, neonates

Question 35

What is bacillus cereus infection classically related to?

Answer 35

Contraction from reheated fried rice (it can survive in extreme temps.)

Question 36

What is the most common parasitic enteric pathogen in the U.S

Answer 36

Giardia lamblia

Question 37

What is giardia lamblia highly associated with?

Answer 37

Contaminated water Most common in young children

Question 38

What are characteristic clinical presentations of giardia?

Answer 38

Foul-smelling, fatty stool, weight loss,

Question 39

What is the other common parasitic enteric pathogen?

Answer 39

Cryptosporidium (C. parvum is most common)

Question 40

What is the most common complication of cryptosporidium infection?

Answer 40

Primary sclerosing cholangitis (infection of biliary system which leads to strictures)

Question 41

What infectious entities should be considered with chronic diarrhea

Answer 41

Giardia, cryptosporidium, entamoeba