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Microbiology > E3- Bacterial Gastro > Flashcards

E3- Bacterial Gastro Flashcards

1
Q

What is the aerotolerance of Enterobacteriaceae?

A

Aerobic, facultative anaerobic

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2
Q

Are Enterobacteriaceae gram positive/negative? What shape?

A

Gram negative bacilli

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3
Q

What are the VF of Enterobacteriaceae?

A
  • Flagella (H antigen)
  • Capsule (K or Vi)
  • LPS (O antigen)
  • Lipid A
  • Fimbriae
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4
Q

What is Enterobacteriaceae’s endotoxin? What can it cause?

A
  • Lipid A component of LPS

- In the blood stream, it can lead to septic shock

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5
Q

What structure allows Enterobacteriaceae to detect the presence of eukaryotic organisms and secrete effector proteins that help the bacteria infect them?

A

T3SS

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6
Q

What Enterobacteriaceae species cause gastroenteritis?

A
  • Salmonella enterica
  • Shigella
  • E. coli
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7
Q

How is Salmonella enterica transmitted?

A

Ingestion of contaminated food or water

  • Poultry
  • Organic vegetables
  • Honey smacks
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8
Q

What is Salmonella enterica serotyping based on?

A

Flagellar (H antigen) and LPS (O antigen)

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9
Q

What structure is unique to Salmonella enterica and is used to invade host epithelial cells and transfer effector proteins?

A

SPI1 T3SSS

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10
Q

What allows Salmonella enterica to cross the intestinal epithelial layer to be phagocytosed by macrophagaes, leading to systemic infection?

A

Effector protein secretion through SPI1 T3SSS

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11
Q

What species is E. coli more closely related to than most of its own strains?

A

Shigella

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12
Q

What are the pathogenic strains of E. coli?

A
  • ETEC (Enterotoxigenic E. coli)
  • EHEC (Enterohemorrhagic E. coli)
  • EIEC (Enteroinvasive E. coli)
  • Shigella species
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13
Q

How is ETEC transmitted?

A

Consumption of contaminated food and water

common in children and travelers

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14
Q

What two types of toxins does ETEC have?

A
  • LT1 (heat labile toxin)

- STb (heat stable toxin)

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15
Q

What ETEC toxin binds to the same receptor as cholera toxin?

A

LT1

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16
Q

What ETEC toxin activates the hosts adenylate cyclase, increasing cAMP levels, leading increased water in the intestine?

A

LT1

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17
Q

What ETEC toxin binds to the guanylate cyclase receptor, increasing cGMP levels, leading to increased water in the intestine?

A

STb

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18
Q

What is another name for EHEC?

A

STEC- Shiga toxin-producing E. coli

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19
Q

What is the most common serotype of EHEC (STEC)?

A

O157:H7

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20
Q

What is a reservoir of EHEC (STEC)? Why does this species not experience symptoms?

A
  • Cattle

- Binds to a receptor that is absent in cattle

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21
Q

How is the Shiga-toxin released from EHEC (STEC) and Shigella?

A
  • No secretion system

- Released after lysogenic bacteriophage is lysed in response to stresses on the bacterial cell

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22
Q

What virulence factor of EHEC (STEC) aid in bacterial binding to the small intestine epithelial cells? What receptor does it bind to?

A
  • Intimin

- Tir receptor

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23
Q

What is the T3SS made by EHEC (STEC) that inserts itself into epithelial cells and then acts as a receptor for intimin?

A

Tir

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24
Q

What does the Tir T3SS made by EHEC (STEC) do once inserted into epithelial cells?

A
  • Acts as receptor for intimin

- Cytoskeletal rearrangement, loss of cell integrity, and death

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25
Q

What species is EIEC basically the same as?

A

Shigella

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26
Q

What type of organism is EIEC?

A
  • Obligate intracellular pathogen
  • No flagella
  • No adhesion factors
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27
Q

Which causative agent of bacterial gastroenteritis causes bloody diarrhea and dysentery?

A

EIEC and Shigella

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28
Q

What is the most virulent strain of Shigella?

A

Shigella dysenteriae

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29
Q

What is the most common type of Shigella infection?

A

Shigella sonnei

30
Q

What differentiates Shigella from E. coli?

A

Shigella is NOT a lactose producer (Lac-, H2S-)

31
Q

How does Shigella leave the gut? What occurs next?

A
  • Leaves the gut via M cells or dendritic cell engulfment
  • Invades and kills macrophages
  • Invades epithelial cells and spreads cell to cell to evade the immune system
  • Leads to extensive damage of the mucosal layer
32
Q

What strain of Shigella produces shiga toxins?

A

Shigella dysenteriae

33
Q

Strains other than Shigella dysenteriae carry toxins that do similar things with less severe outcomes. What are these toxins called?

A

ShET1 and ShET2

34
Q

Does Salmonella, E. coli, or Shigella have a hose dose infective rate?

A

Salmonella (does not spread person-to-person)

35
Q

Does Salmonella, E. coli, or Shigella have a low dose infective rate?

A

E. coli and Shigella (can easily spread person-to-person)

36
Q

What type of agar is used to culture Salmonella, E. coli, and Shigella?

37
Q

Is Salmonella, E. coli, or Shigella lactose producing?

A

E. coli (Lac+, H2S-)

38
Q

Is Salmonella, E. coli, or Shigella H2S producing?

A

Salmonella (Lac-, H2S+)

39
Q

Besides MacConkey agar, what other type of can Salmonella be plated on to show H2S production?

40
Q

Why are abx not given to tx Shigella and EHEC symtoms?

A

They can cause D+ HUS which is worsened by inappropriate use of abx

41
Q

Is Vibrio cholerae gram positive/negative? What shape?

A

Gram negative, curved rod

42
Q

What is the function of the cholera A-B toxin?

A
  • Activates adenylate cyclase
  • Increased cAMP causes cell to secrete chloride ions
  • Na and water follow
43
Q

What is the clinical presentation of Vibrio cholerae?

A
  • Profuse watery diarrhea (20L/day)

- Severe dehydration

44
Q

How is Vibrio cholerae transmitted?

A
  • Fecal-oral

- Oysters

45
Q

What is the clinical presentation of C. diff?

A
  • Watery diarrhea

- Colitis, pseudomembraneous colitis

46
Q

Is C. diff gram positive/negative? What shape? What areotolerance?

A

Gram positive bacili

Obligate anaerobe

47
Q

What do C. diff species produce?

A

Endospores

48
Q

What type of pathogen is C. diff?

A

Opportunistic pathogen

primarily in hospitalized patients or patients on abx therapy

49
Q

How is C. diff treated?

A
  • Stop abx (if possibe)
  • Fecal transplant
  • Isolate pts
50
Q

What is the only effective way to kill endospores?

51
Q

What does the growth of Campylobacter require?

A

Specific gas concentrations

52
Q

Are Campylobacter gram positive/negative? What shape?

A

Gram negative spiral bacili

53
Q

What virulence factors does Campylobacter have?

A

Adhesions (chick colonization)
Capsule
LOS

54
Q

Does Campylobacter have a high or low infectious dose?

A

Low infectious dose

55
Q

What is a rare complication of a Campylobacter infection?

A

Guillain-Barre syndrome (symmetric weakness)

56
Q

How does Campylobacter cause symmetic weakness in Guillain-Barre syndrome?

A
  • LOS resembles human neuronal gangliosides

- Infection leads to cross-reactive antibodies

57
Q

How is Campylobacter dx?

A
  • S shaped organism in stool smaple

- Antibody kit (campy antigens)

58
Q

What does Helicobacter pylori produce?

59
Q

What is unique about the colonization of H. pylori?

A

It lives in the mucosal layer over the STOMACH epithelial cells

60
Q

What is the clinical presentation of H. pylori

A
  • Gastric ulcers

- Gastric cancer

61
Q

What virulence factors does H. pylori have?

A
  • VacA

- CagA

62
Q

What H. pylori strains are more likely to produce gastric cancer?

A

Cancer = cagA (East Asia)

63
Q

How is H. pylori dx?

A
  • Histology exam of gastric biopsy (urease)

- Antigen detection in stool sample

64
Q

How is Clostridium perfringens transmitted? Why is there no fever?

A
  • Foodborne intoxication (ingestion of meat contaminated with toxins-potlucks)
  • Toxin-based
65
Q

Are Bacillus species gram positive/negative? What shape?

A

Gram positive rods

66
Q

What do Bacillus species produce?

67
Q

What disease do Bacillus cereus heat stable enterotoxin produce? Why is there no fever?

A
  • Emetic disease (from contaminated rice)

- Toxin-based

68
Q

What disease do Bacillus cereus heat labile enterotoxin produce? Why is there a fever?

A
  • Diarrheal disease

- True infection with bacterial replication

69
Q

Are staphylococcus gram positive/negative? What shape?

How can you distinguish Staph species?

A

Gram positive cocci

Catalase + test

70
Q

What temperatures can Staph species grow at?

A

15-40 (wide range)

71
Q

What virulence factor do Staph species have? Is there an associated fever?

A
  • Superantiegens (heat labile, but resistant to gastric enzymes; mainly S. aureus)
  • No fever

Microbiology (23 decks)

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