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Owenbacteria Block 2 > GI Pathogens > Flashcards

GI Pathogens Flashcards

1
Q

What gram-positive, non-spore forming rod that is catalase positive and beta-hemolytic on blood agar has a characteristic tumbling motility?

A

Listeria monocytogenes

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2
Q

What are 5 methods of obtaining a Listeria monocytogenes infection?

A
  1. Ingestion of contaminated raw milk or cheese from infected cows
  2. Undercooked processed meats
  3. Unwashed raw vegetables
  4. Vaginally (during birth)
  5. Transplacental infection of fetus from bacteremic mother.
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3
Q

What are the 3 characteristics of L. monocytogenes morphology?

A
  1. Gram-positive rod
  2. Non-spore forming
  3. Motile - tumbling motility at 25C
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4
Q

What are 3 characteristics of L. monocytogenes metabolism?

A
  1. Facultative anaerobe
  2. Catalase - positive
  3. Beta-hemolytic
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5
Q
  1. How does *L. monocytogenes *create its movement? What antigen is associated with this?
  2. What creates its heomlytic capability? What properties does this substance have?
A
  1. It has flagella, so it has H-antigen
  2. Hemolysin (similar to streptolysin-O). It is heat labile and antigenic.
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6
Q
  1. What two toxins does L. monocytogenes secrete?
  2. What do these toxins do?
A
  1. Listeriolysin O and phospholipases
  2. Allows escape from phagolysosomes of macrophages.
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7
Q

What are three clinical conditions that can develop from L. monocytogenes?

A
  1. Neonatal meningitis
  2. Meningitis in immunosuppressed patients and the elderly.
  3. Septicemia in pregnant women (usually during 3rd trimester when immune system is weakest)
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8
Q
  1. What is the appropriate antibiotic treatment for L. monocytogenes?
  2. What is it naturally resistant to?
A
  1. Gentamycin & Penacillin/Ampicillin combination therapy.
  2. Naturally cephalosporin resistant
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9
Q

What are the two CDC associated outbreaks of Listeria from?

A

Cantaloupes and Ricotta cheese

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10
Q

*Listeria *becomes less motile by flagella at 37C and higher, so how does it move through the host cell?

A

It develops an ActA based actin polymerization using the host’s cytoskeleton. This acts like a “comet tail”

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11
Q
  1. Is the normal gastroduodenal environment sufficient to sterilize L. monocytogenes?
  2. Listeria is a facultative intracellular parasite, what cells does it first enter and where?
  3. What stimulates the activity of listeriolysin O and Listeria’s phospholipases?
  4. Where does L. monocytogenes freely replicate?
A
  1. No, it can survive both gastric acid and bile salts.
  2. Enterocytes or M-cells in Peyer’s patches.
  3. A drop in pH in the phagosome.
  4. In the cytoplasm.
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12
Q

How is L. monocytogenes isolated from mixed flora in culture?

A

It can grow at temperatures as low as 2.5C. So using a cold enrichment technique will isolate it.

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13
Q
  1. Where is Salmonella typhi found?
  2. Where are non-typhi Salmonella groups found?
  3. By what route is S. typhi transmitted?
A
  1. Only in humans
  2. Pet turtles - Chickens - undercooked eggs
  3. Fecal - Oral
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14
Q

What morphology do the Enterobacteriaceae family bugs, Salmonella, Shigella, and E. coli have in common?

A

They are all Gram negative rods

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15
Q

What metabolic characteristic differentiates *E. coli *from *Salmonella *or Shigella?

A

E. coli ferments lactose and the others do not

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16
Q

If Shigella and Salmonella are both non-lactose fermenting what metabolic trait differentiates them?

A

Salmonella produces H2S and Shigella does not produce it.

17
Q

What serologic antigens would a Salmonella infection be positive for and what do they represent? (3 items)

A

H antigen - flagellar proteins

VI antigen - capsular proteins

O antigen - LPS

18
Q

Which of the three Enterobacteriaceae organisms for this course is a siderophore?

A

Salmonella

19
Q

What toxins is Salmonella associated with?

A

None

20
Q
  1. What are the clinical hallmarks of S. typhi related typhoid fever?
  2. How does S. typhi spread to other locations?
A
  1. Fever - Abdominal pain - Hepatosplenomegaly - Rose spots on abdomen
  2. Through the reticuloendothelia system
21
Q

How does non-typhi Gastroenteritis create its symptoms?

A

Induction of inflammatory response
Disruption of enterocytes → malabsorption
Release of PGs → increase in cAMP → watery diarrhea

22
Q
  1. Is there a typhoid vaccine? What type of vaccine is it?
  2. What is the anti-biotic treatment for a Salmonella infection?
  3. Should all Salmonella infections be treated with anti-biotics?
A
  1. There are two - A live attenuated vaccine Ty21a and a VI polysaccharide vaccine, Typhim.
  2. Ampicillin & Bactrim or Cipro
  3. No, gastroenteritis only infections should not
23
Q

How would you obtain a culture of S. typhi from a suspected patient?

A

From stool

24
Q

S. typhi is a facultative intracellular parasite that can live in carriers for years. Where does it hide out?

A

In the gallbladder. *S. typhi *is shed in carriers stool (Typhoid Mary)

It can also live within macrophages in lymph nodes

25
Q

What type of people are at increased risk of having a clinically significant Salmonella infection?

A

People who are asplenic (particularly SCD patients)

26
Q

How is Shigella different from Salmonella metabolically?

A

Shigella does not produce H2S.

27
Q
  1. What intestinal cells does Shigella invade?
  2. How does it promote its own engulfment?
  3. Where in the cell does it replicate?
  4. How does Shigella promote intestinal inflammation?
A
  1. M cells of Peyer’s patches
  2. Injects type III “effectors” w/ instructions for engulfment (These “effectors” are Invasion Protein Antigens, IpaA,B,C,D)
  3. In the cytoplasm
  4. S. dysenteriae induced apoptosis releases IL-1
28
Q
  1. What are the clinical symptoms of a Shigella?
  2. What is the treatment?
  3. What is the only reservoir for Shigella?
  4. Why should anit-diarrheals be avoided?
A

Bloody diarrhea with mucus and pus

  1. Ampicillin, Bactrim, Ceftriaxone
  2. Humans
  3. They worsen illness by trapping toxin in gut.
29
Q

How long after ingestion of Shigella do symptoms develop?

A

1-3 days

30
Q

What are metabolic commonalities between all enterobacteriaceae?

A

All are:

  1. Catalase-positive
  2. Oxidase-negative
  3. Ferment glucose
  4. Facultative anaerobes
31
Q

What is the structural commonality of *E.coli, Shigella, *and Salmonella?

A

They are all Gram negative rods

32
Q

What is unique about E. coli metabolicaly compared to *Salmonella, *and Shigella? (3 items)

A
  1. It is Indole positive (makes indole from tryptophan)
  2. It is Beta-hemolytic
  3. It ferments lactose
33
Q

What are 5 virulence factors for E.coli**?

A
  1. Fimbriae (pili): a colonization factor
  2. It is a siderophore
  3. It has adhesins
  4. It has a capsule (K-antigen)
  5. It has flagella (H-antigen)
34
Q

What three toxins are associated with E. coli**?
What do they do?

A
  1. LT (heat labile) - increases cAMP (sames as cholera toxin)
  2. ST (heat stable) - increases cGMP
  3. Shiga-like toxin (verotoxin) - inhibits protein synthesis by inactivating 60S
35
Q
  1. How can normal E. coli be differentiated from EHEC using MacConkey agar?
A
  1. Normal E.coli will appear pink because it CAN ferment sorbitol while EHEC appears colorless because it cannot ferment sorbitol.
36
Q
A

Owenbacteria Block 2 (12 decks)

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