Acute Infectious Diarrhea

Question 1

Pathogenesis of acute infectious diarrhea

Answer 1

• bacterial toxins (enterotoxin-producing bacteria) and entero-adherent pathogens both lead to small bowel hypersecretion, leading to vomiting, profuse watery diarrhea
• cytotoxin-producing and invasive microorganisms cause high fever and abdominal pain

Question 2

physical findings in diarrhea

Answer 2

• vitals: fever, hypotension, tachycardia
• signs of dehydration (could be mild, moderate, severe)
• abdominal exam: increased bowel sounds with diarrhea

Question 3

origin of acute infectious diarrhea

Answer 3

usually from fecal-oral transmission (via ingestion of contaminated food/water)
-note: most are mild/self-limited, no workup

Question 4

what diarrheal signs indicate need for workup?

Answer 4

• profuse diarrhea and dehydration
• hypotension & tachycardia
• dysentery (bloody diarrhea with leukocytes)
• fever >101
• duration >48hrs
• recent antibiotic use
• associated severe abdominal pain
• immunocomp or elderly pts
• increased creatinine (>1.5x normal)
• peripheral leukocytes >15,000

Question 5

what serum workup for acute infectious diarrhea?

Answer 5

-CBC, electrolytes, BUN, Cr, Blood culture
Looking for: leukocytosis? anemia? thrombocytopenia? hypokalemia? acute kidney injury? hemolytic uremic syndrome (HUS)? bacteremia?

Question 6

what other workup is needed?

Answer 6

microbiologic stool analysis (looking for:)
-salmonella
-shigella/shiga toxin
-e.coli
-campylobacter
takes 24-48 hrs
-stool antigen can also be tested for

Question 7

if culture is negative, next workup?

Answer 7

• endoscopy and biopsy may be needed

- may do xray (ileus, toxic megacolon), abdominal CT w/ contrast (sensitive for free air/perforation, colitis)

Question 8

Bacterial Diarrhea

Answer 8

• from “food poisoning”
• chicken= campylobacter, shigella, salmonella
• hamburger= enterohemorrhagic E. coli
• fried rice= bacillus cereus
• potato salad= s. aureus
• eggs=salmonella
• lunch meat=listeria
• seafood= vibrio species, salmonella, acute Hep A, Norwalk, campylobacter

Question 9

staphylococcus aureus

Answer 9

-gram positive+ cocci (clusters/grape like)
-preformed enterotoxins
Sx: N/V, watery diarrhea, rapid onset w/in 6hrs
-resolved 24-48hrs
risk: eggs, mayo, potato salad, cream pastries

Question 10

bacillus cereus

Answer 10

-gram positive+ rod
-preformed enterotoxins
Sx: Vomiting, watery diarrhea, rapid onset w/in 6hrs
-resolved 24-48hrs
risk: fried rice

Question 11

clostridium perfringens

Answer 11

-gram positive+, spore forming rod (heat resistant)
-preformed enterotoxins
Sx: crampy abdominal pain, watery diarrhea, rapid onset w/in8-16hrs (must have consumed large amount)
-resolved 24-48hrs
risk: beef, ham, legumes, gravy, heat resistant spores inadequately cooked

Question 12

shigella

Answer 12

-gram negative rods
-lack flagella, non-motile
-toxin mediated (enterotoxin shiga toxin)
Sx: starts as watery diarrhea, becomes small volume diarrhea and bloody (dysentery), abdominal cramps, fever for 3-4 days
-lasts 1-2 weeks
Dx: fecal leukocytes, stool culture (similar to IBD)
risk: lettuce, raw veggies
**post infectious complication: Reactive arthritis

Question 13

salmonella typhimurium

Answer 13

-gram negative rod (non motile, non lactose fermenting)
-organisms travel through peyer’s patches, most US cases are “non-typhoidal”
Sx: watery diarrhea and later bloody diarrhea, fever, abdominal cramping, n/v, fecal leukocytes
risk: food, reptiles, HIV/sickle cell patients
**post infectious complication: septic arthritis, abscess, osteomyelitis

Question 14

salmonella typhi (typhoid fever)

Answer 14

-gram negative rod (anaerobic)
-organisms enter via peyer’s patches, lives only in humans and their stool (fecal-oral transmission)
-can have asymptomatic carriers “typhoid mary”, colonizes gallbladder
Sx: typhoid fever, 7-14 days post ingestion, “rose spots”, 2 symptomatic phases, “pea soup diarrhea” to later bloody diarrhea
Dx: stool culture, blood culture

Question 15

campylobacter jejuni

Answer 15

-gram negative rod (curved/spiral shaped)
-natural host=wild birds/ducks
Sx: watery diarrhea to bloody diarrhea, fever, cramping, erythema nodosum
Dx: fecal leukocytes, stool culture “campy blood agar”
risk: undercooked poultry
**complications: Guillian-Barre’ Syndrome

Question 16

vibrio cholerae

Answer 16

-gram negative bacilli (anaerobic, curved)
-toxin production
Sx: n/v/cramping, watery, profuse “rice water” diarrhea (1L/hr), vomiting and dehydration/electrolyte imbalance, can be deadly
Dx: stool microscopy, gram stain of stool specimen
Risk: waterborne illness, raw oysters, underdeveloped nations
**must rehydrate/replace electrolytes!

Question 17

vibrio parahemolyticus

Answer 17

-gram negative bacilli
-cytotoxin production
Sx: n/v/cramps, watery to bloody diarrhea, lasts 2-5 days
Dx: fecal leukocyte, stool culture
Risk: seafood

Question 18

vibrio vulnificus

Answer 18

-gram negative bacillus
Sx: v/d/ cramping within 16 hrs, open wound in the water (“bullous skin lesions”), especially in pts with cirrhosis/immunocomp
risk: warm, shallow, coastal salt water, eating raw oyster

Question 19

aeromonas hydrophila

Answer 19

-gram negative, non spore forming rod shaped, facultative anaerobe, motile with flagella, enterotoxins
Sx: 2 types- cholera like (non blood diarrhea/rice water) and bloody mucoid stools
Risk: fresh water, eating seafood, open wounds in water

Question 20

Traveler’s Diarrhea (TD)

Answer 20

-3 days to 2 wks after travel (contaminated water/food)
Sx: watery diarrhea, N/V, cramps, fatigue
-self limited, lasts 1-5days
risk: travel to developing countries, H2 blocker/PPI use are risk factors
-MC pathogen for TD: enterotoxigenic E. coli (ETEC), other causes including giardia possible

Question 21

ETEC (enterotoxigenic E. Coli)

Answer 21

-gram negative rod
Sx: N/V, watery diarrhea, occasional fever, sudden onset
Dx: usually dx clinically

Question 22

EHEC (enterohemorrhagic E. Coli)

Answer 22

-gram negative rod, produces shiga-like toxin
Sx: watery to bloody diarrhea, MC cause of acute hemorrhagic colitis, abdominal tenderness, no fever
Dx: CBC, peripheral leukocytes, anemia, thrombocytopenia, stool culture: shiga like toxin
Risk:undercooked hamburger
Tx: supportive, rehydration
**complication= HUS (hemolytic uremic syndrome), more common in pts who received antibiotics

Question 23

yersinia enterocolitica

Answer 23

-gram negative coccobacilli
-transmitted by contaminated food/dairy
Sx: bloody diarrhea with fever, Right sided abd pain, can mimic appendicitis or crohn’s disease
Dx: stool/blood cultures, clinically cant distinguish from salmonella or shigella
Risk: higher affinity for iron overload symptoms

Question 24

Listeria monocytogenes

Answer 24

-gram positive+ rod (can grow in the cold!)
-Sx: fever, non bloody diarrhea, n/v, in pregnant patients sx can be non specific
Dx: blood culture or CSF (stool culture wont grow listeria)
Risk: anyone can get it, concern for pregnant women, avoid deli meats

Question 25

Tropheryma whipplei (“Whipple Disease”)

Answer 25

-rare multi system disease
-gram positive+ bacilli, not acid fast
Sx: arthralgia, weightloss, malabsorption, chronic diarrhea
Dx: endoscopy with duodenal biopsy, PAS (periodic acid schiff) positive macrophages with characteristic bacillus
Tx: antibiotics, if untreated, fatal

Question 26

Clostridium difficile (c. diff)

Answer 26

-gram positive+, spore forming bacillus, anaerobic
-cytotoxin producing
Sx: watery diarrhea, abd pain, fever
Dx: stool assay (PCR for toxin A and B), pseudomembranes on colonic mucosa
Risk: antibiotic use
**complication: toxic megacolon

Question 27

Rotavirus

Answer 27

-infants under 2 (winter months), acute diarrhea
-double stranded RNA virus, spread fecal-oral
Sx: vomiting, watery diarrhea (sever dehydration), sx begin within 72 hrs
Dx: viral culture/PCR, on electron microscopy (“wagon-wheel” appearance)

Question 28

Adenovirus (serotypes 40 & 41)

Answer 28

-double stranded DNA virus
Sx: fever, chills, myalgias, watery diarrhea/vomiting, conjunctivitis, pharyngitis, may last up to 10 days
Dx: viral culture

Question 29

Norwalk Virus (Norovirus)

Answer 29

-small, non enveloped RNA virus, fecal-oral transmission
-think nursing homes, cruise ships
Sx: vomiting, watery diarrhea, symptoms within 24-48hrs
Dx: viral cultures dont say much, work up not needed

Question 30

Cytomegalovirus (CMV)

Answer 30

-double stranded linear DNA
-think immunosupp pts (AIDS with CD4 <200)
Sx: fever, abd pain, bloody diarrhea, lasts for weeks
Dx: endoscopy with biopsy of ulcerated lesions using CMV specific stains