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Enteric Bacteria Flashcards

1
Q

In humans, what is the predominant species of gram negative bacilli in the colonic flora?

A

E. coli

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2
Q

What group of bacteria are the most common cause of septic shock?

A

Gram negative bacilli

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3
Q

After ETEC colonize the GI tract it releases toxins that mediate diarrheal illness. What are these toxins? What messenger systems do they act on?

A

Heat-labile enterotoxin (activates AC)

Heat-stabile enterotoxin (activates GC)

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4
Q

Detail the diarrhea associated with ETEC.

A

Watery

Lacks inflammatory cells

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5
Q

What serotype is the most common E.coli strain that causes bloody diarrhea?

A

O157:H7

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6
Q

What is the classic triad of hemolytic uremic syndrome?

A

Anemia
Renal failure
Thrombocytopenia

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7
Q

How can you distinguish EHEC from other E. coli?

A

They do not ferment sorbitol

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8
Q

What is the major reservoir for EHEC?

A

Cattle- often contaminated during food processing, manure can contaminate produce/water supply

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9
Q

EHEC secrete Shiga-toxin; detail the structure and function of this toxin.

A

A subunit- inactivates 60S ribosome

5 B subunits- bind to microvilli

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10
Q

EPEC typically causes diarrhea in children. Describe the effect of this pathogen on the gastric mucosa.

A

Colonizes mucosa

Effacement of microvilli

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11
Q

EIEC shares many genetic and clinical features with what other organism?

A

Shigella

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12
Q

Compare the sign of fever in EIEC and EHEC.

A

EIEC- fever is present

EHEC- fever is absent

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13
Q

What is the mainstay of treatment for all diarrheal syndromes?

A

Replacement of water and electrolytes

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14
Q

Should antimicrobial therapy be initiated in a patient with EHEC?

A

No- may increase incidence of HUS

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15
Q

Acquisition of what virulence factor enable E. coli to cause cystitis/pyelonephritis?

A

Pili

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16
Q

What is the most common causative organism of a UTI?

A

E. coli

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17
Q

What genera are gram-negative bacilli that are non-lactose fermenters and oxidase negative?

A

Salmonella

Shigella

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18
Q

Detail the process by which Shigella infect intestinal epithelial cells.

A

Enter M cells and cross epithelial border
Taken up by macrophages- cause apoptosis of macrophages
Enter basal side of epithelial cells
Move between epithelial cells- commandeer cytoskeleton components (amotile)

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19
Q

Which has the greater impact on disease caused by Shigella, invasion or Shiga toxin?

A

Invasion

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20
Q

What is the first line treatment for Shigellosis?

A

Ciprofloxacin

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21
Q

How is Shigella spread?

A

Fecal oral route

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22
Q

What is the leading cause of bacterial gastroenteritis? What is the second leading cause of bacterial gastroenteritis?

A

Campylobacter

Salmonella

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23
Q

What are the virulence factors of Salmonella typhi?

A

Endotoxin

Vi capsule- inhibits Ab binding to O antigen

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24
Q

Contrast the reservoirs for S. typhi and S. enterica.

A

Enterica- many hosts

Typhi- human host only

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25
Q

How is Salmonella transmitted?

A

Fecal-oral route

26
Q

What is the characteristic rash of typhoid fever?

A

Rose spots on abdomen

27
Q

Detail the different vaccines available for Salmonella typhi. Who should be offered a vaccine?

A

Oral- live, attenuated S. typhi
IM- Vi capsular polysaccharide
Offer to people traveling to areas where Typhoid fever is endemic

28
Q

What is the first line treatment for Typhoid fever?

A

Fluoroquinolone

29
Q

What are classic sources of nontyphoid Salmonella?

A

Poultry
Eggs
Turtles

30
Q

After exposure to S. typhi some individuals continue to spread the bacteria even though they do not exhibit symptoms. Typhoid Mary is an example of such a person. How does this occur?

A

Bacteria colonize the gallbladder and are constantly secreted

31
Q

Salmonella invades M cells and is then taken up by mononuclear phagocytes. Where does salmonella multiply?

A

In monocytes

32
Q

Yersiniosis is a zoonotic infection with an enteropathogenic Yersinia species, usually Y. enterocolitica or Y. pseudotuberculosis. Both organisms may cause self-limiting diarrhea and present very similarly to what disease?

A

Appendicitis (cause pseudoappendicits)

33
Q

Consumption of what food is strongly linked with Yersinia infection?

34
Q

Detail the typical route of infection of Y. enterocolitica.

A

Oral ingestion
Initial replication in small intestine
Invasion of Peyer’s patches via M cells
Spread to mesenteric lymph nodes

35
Q

Like other invasive infections of intestinal origin (salmonellosis, shigellosis), reactive arthritis can develop. The majority of individuals affected by reactive arthritis have what HLA haplotype?

36
Q

What bacteria are gram negative comma shaped organisms?

A

Campylobacter
V. cholerae
H. pylori

37
Q

How can you differentiate between gram negative comma shaped organisms?

A

C. jejuni grows at 42 degrees C
V. cholerae grows in alkaline media
H. pylori produces urease

38
Q

Cholera refers to disease caused by which V. cholera serogroups?

39
Q

What is the natural habitat of V. cholerae?

A

Coastal salt water

Brackish estuaries

40
Q

For unexplained reasons, susceptibility to cholera is significantly influenced by ABO blood group status. What blood group puts patients at greatest risk for serious disease?

41
Q

What virulence factor is essential for V. cholerae to survive and multiply in the small intestine?

A

Toxin coregulated pilus

42
Q

What effect does the A subunit of cholera toxin have on intestinal epithelial cells?

A

Increases activity of AC
Inhibits absorption of Na
Increases secretion of Cl

43
Q

If fluids/electrolytes are not restored in a person with cholera, what happens?

A

Shock (dehydration)

Acidosis (loss of bicarb)

44
Q

If a patient with cholera is not rehydrated what can happen to their kidneys?

A

Volume depletion can lead to pre renal azotemia and AKI

45
Q

How do people with cholera die?

A

Hypovolemic shock

46
Q

You are in a region with endemic cholera and develop watery diarrhea. You do not have access to medical care, but you do have fresh water, salt, and sugar. How can you mix an oral rehydration solution?

A

1 L water
2 Tbl sugar
1/2 tsp salt

47
Q

What species of campylobacter is the principle diarrheal pathogen and which is the primary cause of extraintestinal illness?

A

Diarrhea- C. jejuni

Extraintestinal- C. fetus

48
Q

What is the most common cause of C. jejuni infection in the US?

A

Ingestion of contaminated poultry

49
Q

Systemic infections by C. fetus most often occur in what group of people?

A

Immunocompromised

50
Q

Describe the diarrhea of C. jejuni infection.

A

Varies from lose stools to grossly bloody stools

51
Q

Campylobacter enteritis may mimic UC or Chron’s disease. and is much more common than either of the two conditions. Can biopsy distinguish these entities?

A

No- do not diagnose IBD until Campylobacter infection has been ruled out

52
Q

What neurologic syndrome can occur following a Campylobacter enteritis?

A

Guillain-Barre syndrome

53
Q

What is the most common bacterial pathogen of humans?

54
Q

Colonization with H. pylori is a risk factor for what diseases?

A

Peptic ulcer
Gastric adenocarcinoma
Gastric MALT lymphoma

55
Q

Colonization with H. pylori may offer some prediction against what diseases?

A

GERD

Esophageal adenocarcinoma

56
Q

What virulence factor produced by H. pylori helps to neutralize the acidic environment of the stomach?

57
Q

H. pylori infection induces what pathologic appearance of the stomach?

A

Chronic gastritis

58
Q

The pattern of gastric inflammation associated with H. pylori infection is associated with certain disease risk; detail this.

A

Antral gastritis-duodenal ulceration

Pan gastritis- gastric ulceration and adenocarcinoma

59
Q

When should you treat H. pylori infection?

A

If patient has gastric/duodenal ulceration or low grade gastric B cell lymphoma

60
Q

What is the first line treatment for H. pylori infection?

A

Triple therapy:
PPI (omeprazole)
Clarithromycin
Amoxicillin

61
Q

If a patient has a penicillin allergy and needs to be treated for H. pylori infection, what drug do you substitute for amoxicillin?

A

Metronidazole

62
Q

What are the H and K antigens?

A

H antigen- flagella

K antigen- capsule

ID (28 decks)

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