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Enteric Bacteria Flashcards

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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
How is Salmonella transmitted?
Fecal-oral route
26
What is the characteristic rash of typhoid fever?
Rose spots on abdomen
27
Detail the different vaccines available for Salmonella typhi. Who should be offered a vaccine?
Oral- live, attenuated S. typhi IM- Vi capsular polysaccharide Offer to people traveling to areas where Typhoid fever is endemic
28
What is the first line treatment for Typhoid fever?
Fluoroquinolone
29
What are classic sources of nontyphoid Salmonella?
Poultry Eggs Turtles
30
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?
Bacteria colonize the gallbladder and are constantly secreted
31
Salmonella invades M cells and is then taken up by mononuclear phagocytes. Where does salmonella multiply?
In monocytes
32
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?
Appendicitis (cause pseudoappendicits)
33
Consumption of what food is strongly linked with Yersinia infection?
Pork
34
Detail the typical route of infection of Y. enterocolitica.
Oral ingestion Initial replication in small intestine Invasion of Peyer's patches via M cells Spread to mesenteric lymph nodes
35
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?
HLA-B27
36
What bacteria are gram negative comma shaped organisms?
Campylobacter V. cholerae H. pylori
37
How can you differentiate between gram negative comma shaped organisms?
C. jejuni grows at 42 degrees C V. cholerae grows in alkaline media H. pylori produces urease
38
Cholera refers to disease caused by which V. cholera serogroups?
O1 | O139
39
What is the natural habitat of V. cholerae?
Coastal salt water | Brackish estuaries
40
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?
O
41
What virulence factor is essential for V. cholerae to survive and multiply in the small intestine?
Toxin coregulated pilus
42
What effect does the A subunit of cholera toxin have on intestinal epithelial cells?
Increases activity of AC Inhibits absorption of Na Increases secretion of Cl
43
If fluids/electrolytes are not restored in a person with cholera, what happens?
Shock (dehydration) | Acidosis (loss of bicarb)
44
If a patient with cholera is not rehydrated what can happen to their kidneys?
Volume depletion can lead to pre renal azotemia and AKI
45
How do people with cholera die?
Hypovolemic shock
46
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?
1 L water 2 Tbl sugar 1/2 tsp salt
47
What species of campylobacter is the principle diarrheal pathogen and which is the primary cause of extraintestinal illness?
Diarrhea- C. jejuni | Extraintestinal- C. fetus
48
What is the most common cause of C. jejuni infection in the US?
Ingestion of contaminated poultry
49
Systemic infections by C. fetus most often occur in what group of people?
Immunocompromised
50
Describe the diarrhea of C. jejuni infection.
Varies from lose stools to grossly bloody stools
51
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?
No- do not diagnose IBD until Campylobacter infection has been ruled out
52
What neurologic syndrome can occur following a Campylobacter enteritis?
Guillain-Barre syndrome
53
What is the most common bacterial pathogen of humans?
H. pylori
54
Colonization with H. pylori is a risk factor for what diseases?
Peptic ulcer Gastric adenocarcinoma Gastric MALT lymphoma
55
Colonization with H. pylori may offer some prediction against what diseases?
GERD | Esophageal adenocarcinoma
56
What virulence factor produced by H. pylori helps to neutralize the acidic environment of the stomach?
Urease
57
H. pylori infection induces what pathologic appearance of the stomach?
Chronic gastritis
58
The pattern of gastric inflammation associated with H. pylori infection is associated with certain disease risk; detail this.
Antral gastritis-duodenal ulceration | Pan gastritis- gastric ulceration and adenocarcinoma
59
When should you treat H. pylori infection?
If patient has gastric/duodenal ulceration or low grade gastric B cell lymphoma
60
What is the first line treatment for H. pylori infection?
Triple therapy: PPI (omeprazole) Clarithromycin Amoxicillin
61
If a patient has a penicillin allergy and needs to be treated for H. pylori infection, what drug do you substitute for amoxicillin?
Metronidazole
62
What are the H and K antigens?
H antigen- flagella | K antigen- capsule

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