Infectious Diarrhea

Question 1

4 aspects of patient history very relevant to determining cause of (infectious) diarrhea?

Answer 1

Travel
Recent hospitalization
Diet
Medications
Medical history (esp immunocompromised)

Question 2

5 signs/symptoms that make diarrhea merit further investigation?

Answer 2

Fever >103F.
Tenesmus
Bloody diarrhea
Prolonged course (>2 weeks)
Dehydration

Question 3

What is tenesmus?

Answer 3

Feeling the urge to pass stool despite bowels being empty.

It is indicative rectal / colon inflammation.

Question 4

5 host factors that increase susceptibility to infectious diarrhea?

Answer 4

Reduced gastric acidity.
Less gastric mucus.
Slowed GI motility
Alterations in gut flora (i.e. ABx)
Systemic and local immune deficiency

Question 5

4 things that bacterial virulence factors can be / promote?

Answer 5

Adhesion
Entertoxins
Cytotoxins
Mucosal invasion

Question 6

What do Cholera enterotoxins A and B do?

Answer 6

A: hits surface epithelium, blocks electrolyte absorption.
B: hits crypts, increases Cl- excretion via cAMP (the one we’ve heard about)

Question 7

What do C. diff cytotoxins do?

Answer 7

Decrease cell-cell adhesion -> electrolyte and water leakage.

Question 8

Diarrhea + fever in adult probably means? In children?

Answer 8

Adults: probably invasive pathogen
Children: probably rotavirus

Question 9

If you’ve got non-bloody infectious diarrhea, what’s the most likely class of organism responsible?

Answer 9

Viruses

then bacteria, then parasites

Question 10

What are the 5 most common viruses causing non-bloody diarrhea?
For which do we have a vaccine?

Answer 10

Calcivirus (Noro and Norwalk-like virus)
Rotavirus - we have vaccine
Adenovirus
Astrovirus
Torovirus

Question 11

4 most common organisms causing food-borne, non-bloody bacterial diarrhea?

Answer 11

Enterotoxigenic E. coli (ETEC)
Diffusely adhering E. coli
V. cholera
other Vibrio

Question 12

3 most common organism causing non-food-borne, non-bloody bacterial diarrhea?

Answer 12

Aeromonas
Bacteroides fragilis
Diffusely adhering E. coli

Question 13

2 parasites causing non-bloody diarrhea (that you actually ever hear about)?

Answer 13

Giardia and cryptosporidium

Question 14

Which E. coli causes bloody diarrhea? What does it make?

Answer 14

Enterohemorrhagic E. coli (EHEC)

It makes Shiga toxin.

Question 15

What do Shigella, Salmonella, Campylobacteria, C. diff, E. histolytica, and Schisto all have in common?

Answer 15

They all cause bloody diarrhea.

Question 16

Broadly, most things that cause tenesmus / proctitis are what? 5 examples? 1 exception?

Answer 16

Are STDs: N. gonorrhea, T. pallidum, Chlamydia, HSV 2.

Exception: Shigella

Question 17

What do C. perfringens, S. aureus, B cereus, C. botulinum, and B. anthracis have in common?

Answer 17

All can cause food-bone diarrhea through their toxins.

Question 18

What do microsporidia, cryptosporidium, cyclospora, isospora, mycobacterium avium complex (MAC), and strongyloides have in common?

Answer 18

Cause non-bloody diarrhea in immunosuppressed patients.

Question 19

What 2 viral organisms cause bloody diarrhea in immunosuppressed patients?

Answer 19

CMV and HSV.

Question 20

Most common type of organisms responsible for traveler’s diarrhea?

Answer 20

Bacteria, specifically ETEC (and EAEC)

Question 21

What is the definition of diarrhea in a hospitalized patient?

Answer 21

Diarrhea that starts 3 days after admission.

Question 22

Diarrhea in a hospitalized patient is pretty much always what?

Answer 22

C. diff.

Question 23

What can you test for in the stool to get a vague idea of whether or not diarrhea is inflammatory? (2 molecules)

Answer 23

Lactoferrin and calprotectin

Question 24

Is testing for fecal leukocytes very useful?

Answer 24

They’re only usually present in a very small number of infections.

Question 25

What additional tests do you do on an immunocompromised patient with diarrhea?

Answer 25

Stool cultures for microsporidia, isospora, etc.

Colonoscopy, upper endoscopy for CMV and MAC lesions.

Question 26

Extra tests for evaluations of Traveler’s diarrhea?

Answer 26

Test stool for…
Aeromonas
Ova and parasites, depending on region traveled to.

Question 27

Micro review: What does C. diff look like on colonoscopy?

Answer 27

Psuedomembranous colitis

Question 28

Among Giardia, Cryptosporidium, Plesiomonas, and Yersina, which is most like to cause food-borne bloody diarrhea in a healthy 20 year old?

Answer 28

Yersinia…
(This is a poor question, as Plesiomonas and Yersinia aren’t among the more common diarrhea-causing organisms. But you should know that giardia = contaminated (beaver pond) water, and crypto = immunocompromised.)

Question 29

2 viruses that can cause chronic diarrhea?

Answer 29

CMV, HSV

Question 30

3 parasites that can cause chronic diarrhea?

Answer 30

E. histolytica, strongyloides, schisto

Question 31

Two causes of chronic absorptive infectious diarrhea?

Answer 31

Whipple’s disease: Tropheryma whipplei
Giardia
(FYI, the yearly incidence of Whipple’s disease is 1 per 1,000,000…. so…)

Question 32

When somebody has chronic diarrhea, what do you first test for?

Answer 32

Non-infectious things: Celiac Abs, TSH, metabolic panel.

And a CBC.

Question 33

What are the preliminary stool tests that should be done for chronic diarrhea? (4 things)

Answer 33

C. diff
Ova and Parasites (Crypto and Giardia)
Culture for Aeromona
Qualitative fecal fat

Question 34

What do high eosinophils in CBC suggest about cause of chronic diarrhea?

Answer 34

Parasite - guy in the case had schisto

Question 35

Which viral diarrhea do you treat?

Answer 35

CMV

Question 36

What bacterial diarrhea do you definitely not want to treat? Why not?

Answer 36

EHEC

Doesn’t help, and increases risk for hemolytic-uremic syndrome (HUS).