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GI > Diarrhea pathogens MOA- #2 > Flashcards

Diarrhea pathogens MOA- #2 Flashcards

1
Q

entamoeba histolytica

A

trophozoite invades colonic epithelium causing local necrosis and dysentery

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2
Q

Where does entamoeba histolytica cyst differentiate into trophozoite?

A

ileum

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3
Q

Diarrheal specimen seen in entamoeba histolytica

A

trophozoite with ingested RBC

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4
Q

Diarrhea with hepatic abscess

A

entamoeba

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5
Q

type of diarrhea seen with entamoeba

A

dystentery (bloody)

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6
Q

After a camping trip to mexico, a patient visits her doctor complaining of loose stools and abdominal cramps. The patient describes the stools as having flecks of blood and lots of mucus. The doctor orders a stool specimen in which she finds motile amoeba with ingested RBCs. She started the patient on metronidazole and considers a CT scan to detect any liver abscesses.

A

entamoeba

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7
Q

A mother brings her 3 year old son to the doctor after severe bouts of vomiting and diarrhea for the past 2 days. The diarrhea is watery, although the mother denies seeing any blood in it. The doctor makes a diagnosis by an elisa on child’s stool and assures the mother he will be fine with good rehydration.

A

rotavirus

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8
Q

Rotavirus: family

A

reoviridae

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9
Q

Rna/dna rotavirus

A

dsRNA, nonenveloped, icosahedral capsid

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10
Q

Type of diarrhea caused by rotavirus

A

watery diarrhea

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11
Q

MOA Rotavirus

A

infects villus cells of proximal small intestine, replicates within and lyses cell, causes impaired absorption of carbs and other nutrients (vomiting, diarrhea)

first aid: villous destruction with atrophy leads to decreased absorption of Na+ and loss of K+

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12
Q

rna/dna norovirus

A

Single stranded positive sense RNA virus, nonenveloped, icosahedral

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13
Q

family: norovirus

A

calicivirus

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14
Q

Thirteen people attending an oyster dinner abruptly develop nausea and abdominal pains 2 days later. Soon after the onset of pain, they begin to vomit and some also have diarrhea.

A

norovirus

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15
Q

Type of diarrhea caused by norovirus

A

watery

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16
Q

MOA: norovirus

A

local infection/inflammation in proximal small intestine causing gastroenteritis

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17
Q

Type of diarrhea: giardia lamblia

A

non-bloody, fatty

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18
Q

Giardia MOA

A

cyst ingested, turns into trophozoite in duodenum, attaches to duodenal wall via suction (not invasive), damages microvilli and causes inflammation, leads to malabsorption

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19
Q

Tear shaped trophozoite with 2 nuclei and 4 mustache flagella

A

giardia

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20
Q

A student cuts short an extended backpacking trip in yosemite park after developing diarrhea. He explains to his doctor that the diarrhea is non-bloody but smells very bad. Upon further questioning, the student tells the doctor that he has been drinking water from a fresh water spring. The patient appears malnourished upon exam. A diarrhea sample reveals 2 nuclei motile amoeba with a tear drop shape and 4 pairs of flagella. The student is given metronidazole.

A

giardia

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21
Q

An HIV patient becomes alarmed after developing a persistent diarrhea. He tells his physician that the diarrhea is watery and without blood. Upon learning that the patient visited a vacation farm before the diarrhea started, the doctor orders an acid-fast stain of the patient’s stool sample.

A

c. parvum

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22
Q

Type of diarrhea caused: cryptosporidium parvum

A

watery

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23
Q

MOA cryptosporidium parvum

A

oocytes ingested, released sporozoites in small intestine, differentiate into trophozoites and attach to intestinal microvilli, watery/non-bloody diarrhea

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24
Q

A photographer for National Geographic returning from Thailand develops a fever and abdominal cramps on the plane. By the time the plane lands, he suffers from bloody diarrhea. His fever peaks at 40 degrees C. The doctor decides to do an endoscopy exam and makes a diagnosis based on the hemorhagic mucosa and ulcerations in the distal colon.

A

shigella

25
Q

Type of diarrhea: shigella

A

bloody (dysentery)

26
Q

Differentiating salmonella vs. shigella

A

shigella does not produce H2S but salmonella does.

27
Q

MOA shigella

A

Shiga toxin inactivates 60S ribosome by removing adenine from rRNA
GI mucosal damage –> dysentery

28
Q

2 pathogens that can cause HUS

A

EHEC, shigella

29
Q

MOA: staph aureus

A

bacteria release toxins in food such as custard, heat stable toxins (preformed) are ingested, gastroenteritis, self-limited

30
Q

A young man enters the ER dehydrated, afebrile, and complaining of nausea and vomiting. Since he began vomiting 1 hour ago, he has been hugging the toilet nearly every 10 minutes. He remembers eating a dish with fried rice at an asian restaurant several hours ago.

A

b. cereus

31
Q

bacillus aerobic or anaerobic?

A

aerobic

clostridium is anaerobic (otherwise exact same gram stain)

32
Q

type of diarrhea: b. cereus

A

watery, nonbloody

33
Q

2 exotoxin mediated food poisoning pathogens

A

s. aureus, b. cereus

34
Q

B. cereus MOA

A

heat labile toxin - increases cAMP, decreases reabsorption of NaCl, diarrhea

during high temp cooking, b. cereus forms protective spores which germinate when food is re-warmed. secretes 2 major antigens, heat stable (vomiting) and heat labile (diarrhea)

35
Q

type of diarrhea: c. perfringens

A

watery

36
Q

c. perfringens MOA

A

heat labile toxin (spores survive cooking, released when reheated) - entertoxin inhibits glucose transport, damages epithelium

37
Q

An old woman comes to the doctor with a fever and loose bowels. Her diarrhea occurs in tremendous volumes, she complains, although she does not remember ever seeing blood. She has an unremarkable recent past medical history, except for an infection a few weeks earlier that was treated with clindamycin. Sigmoidoscopy of her colon reveals yellow-white plaques, which the doctor predicted after analyzing her stools for toxins.

A

c. diff

38
Q

MOA c. diff

A

C. diff is normal flora of gut, spores germinate following an antibiotic treatment, grow rapidly and release 2 toxins:
Toxin A: alters fluid secretion (watery diarrhea) - binds brush border of gut
Toxin B: cytotoxic to epithelial cells (pseudomembrane) - causes cytoskeletal disruption via actin depolymerization

39
Q

Type of diarrhea: c. diff

A

watery

40
Q

A man and his two sons just returned from a vacation on their relative’s farm. All three arrive complaining of bloody diarrhea. The youngest becomes well spontaneously. The older son complains of right flank pain, while the father starts to notice tenderness in his joints. One surgeon, worried about appendicitis in the older son, performs the initial incisions and discovers a normal appendix but an inflamed colon. After also observing swollen mesenteric lymph nodes during surgery, he makes a diagnosis explaining the symptoms in all three patients.

A

yersinia

41
Q

Type of diarrhea: yersinia

A

bloody diarrhea

42
Q

Yersinia MOA:

A

invades and causes local inflammation, spreads to the colon, ulcerates colon and produces dysentery like symptoms.

43
Q

Yersinia can mimic:

A

appendicitis or Crohns

44
Q

Manifestations of yersinia in diff age groups

A

5: bloody diarrhea + appendicitis like symptoms
adult: bloody diarrhea and arthritis

45
Q

A man visiting india arrives in the ER with signs of severe dehydration. He is thirsty, has decreased skin turgor, tachycardia, and somnolence. He abruptly began to suffer from diarrhea this morning and complains about the magnanimous watery volumes he is excreting. He has no fever and the doctor treats with fluid and electrolytes.

A

Vibrio cholera

46
Q

Type of diarrhea: cholera

A

rice-water, watery

47
Q

cholera MOA:

A

cholera toxin overactivates adenylate cyclase (increases cAMP) by permanently activating Gs - increases Cl- secretion in gut and H2O efflux

48
Q

A series of patients in a small town visit the hospital complaining of bloody diarrhea, fatigue, and confusion. Physical exams reveal neurological deficits and lab tests show anemia, thrombocytopenia, and uremia. Peripheral blood smears show fragmented rbcs, but subsequent coombs tests are negative. After careful questioning, the doctors discover that each patient frequents the same fast-food burger joint. The physicians identify the causative agent with serological testing and stool cultures appearing metallic green.

A

EHEC

49
Q

EHEC MOA

A

adheres to colonic epithelium, does not invade, secretes shiga-like toxins causing inflammation and bleeding leading to dysentery

If shiga-like toxin enters blood stream, HUS

Also inactivates 60S ribosome , blocks protein synthesis, causing cell death

50
Q

differentiating EHEC from other E coli

A

does not ferment sorbitol

51
Q

ETEC moa

A

adheres to jejunum and ileum but does not invade, produces heat labile toxin and heat stable toxin, causes watery diarrhea

HL toxin: increases adenylate cyclase (cAMP), increases Cl secretion and causes H2O efflux (similar to cholera)

Heat stable: over-activates guanylyl cyclase, decreases resorption of NaCl and H20 in the gut (similar to yersinia)

52
Q

Shigella vs. EHEC

A

shigella is invasive, EHEC is not.

53
Q

A man with fever, muscle pains, and headache feels no need to go to the doctor until 1 day later, when he develops diarrhea and abdominal pain as well. The abdominal pain is so severe that his physician fears appendicitis until learning that the man may have consumed unpasteurized milk in the past week. A definitive diagnosis is made by growth on stool culture at 42 degrees C, microaerophilic conditions.

A

c. jejuni (MILK! DEDUDHNI!)

54
Q

c. jejuni MOA

A

colonizes terminal ileum/colon, often invates, may release cholera like toxin and cytotoxin, watery, ill smelling diarrhea preceding bloody stools

55
Q

type of diarrhea: c. jejuni

A

watery, ill smelling that becomes bloody. or just bloody

56
Q

A veterinary school student complains to the doctor of diarrhea and abdominal tenderness. He is certain that these symptoms followed nausea and vomiting the day before. He admits that he may have caused himself this misery by playing excessively with his turtle.

A

Salmonella.

57
Q

Salmonella vs. shigella

A

salmonella produces H2S, motile (shigella is nonmotile and doesnt produce H2S)

58
Q

type of diarrhea: salmonella

A

bloooody

GI (4 decks)

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