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E3- Bacterial Gastro Flashcards

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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
What species is EIEC basically the same as?
Shigella
26
What type of organism is EIEC?
- Obligate intracellular pathogen - No flagella - No adhesion factors
27
Which causative agent of bacterial gastroenteritis causes bloody diarrhea and dysentery?
EIEC and Shigella
28
What is the most virulent strain of Shigella?
Shigella dysenteriae
29
What is the most common type of Shigella infection?
Shigella sonnei
30
What differentiates Shigella from E. coli?
Shigella is NOT a lactose producer (Lac-, H2S-)
31
How does Shigella leave the gut? What occurs next?
- 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
What strain of Shigella produces shiga toxins?
Shigella dysenteriae
33
Strains other than Shigella dysenteriae carry toxins that do similar things with less severe outcomes. What are these toxins called?
ShET1 and ShET2
34
Does Salmonella, E. coli, or Shigella have a hose dose infective rate?
Salmonella (does not spread person-to-person)
35
Does Salmonella, E. coli, or Shigella have a low dose infective rate?
E. coli and Shigella (can easily spread person-to-person)
36
What type of agar is used to culture Salmonella, E. coli, and Shigella?
MacConkey
37
Is Salmonella, E. coli, or Shigella lactose producing?
E. coli (Lac+, H2S-)
38
Is Salmonella, E. coli, or Shigella H2S producing?
Salmonella (Lac-, H2S+)
39
Besides MacConkey agar, what other type of can Salmonella be plated on to show H2S production?
SS agar
40
Why are abx not given to tx Shigella and EHEC symtoms?
They can cause D+ HUS which is worsened by inappropriate use of abx
41
Is Vibrio cholerae gram positive/negative? What shape?
Gram negative, curved rod
42
What is the function of the cholera A-B toxin?
- Activates adenylate cyclase - Increased cAMP causes cell to secrete chloride ions - Na and water follow
43
What is the clinical presentation of Vibrio cholerae?
- Profuse watery diarrhea (20L/day) | - Severe dehydration
44
How is Vibrio cholerae transmitted?
- Fecal-oral | - Oysters
45
What is the clinical presentation of C. diff?
- Watery diarrhea | - Colitis, pseudomembraneous colitis
46
Is C. diff gram positive/negative? What shape? What areotolerance?
Gram positive bacili | Obligate anaerobe
47
What do C. diff species produce?
Endospores
48
What type of pathogen is C. diff?
Opportunistic pathogen | primarily in hospitalized patients or patients on abx therapy
49
How is C. diff treated?
- Stop abx (if possibe) - Fecal transplant - Isolate pts
50
What is the only effective way to kill endospores?
Autoclave
51
What does the growth of Campylobacter require?
Specific gas concentrations
52
Are Campylobacter gram positive/negative? What shape?
Gram negative spiral bacili
53
What virulence factors does Campylobacter have?
Adhesions (chick colonization) Capsule LOS
54
Does Campylobacter have a high or low infectious dose?
Low infectious dose
55
What is a rare complication of a Campylobacter infection?
Guillain-Barre syndrome (symmetric weakness)
56
How does Campylobacter cause symmetic weakness in Guillain-Barre syndrome?
- LOS resembles human neuronal gangliosides | - Infection leads to cross-reactive antibodies
57
How is Campylobacter dx?
- S shaped organism in stool smaple | - Antibody kit (campy antigens)
58
What does Helicobacter pylori produce?
Urease
59
What is unique about the colonization of H. pylori?
It lives in the mucosal layer over the STOMACH epithelial cells
60
What is the clinical presentation of H. pylori
- Gastric ulcers | - Gastric cancer
61
What virulence factors does H. pylori have?
- VacA | - CagA
62
What H. pylori strains are more likely to produce gastric cancer?
Cancer = cagA (East Asia)
63
How is H. pylori dx?
- Histology exam of gastric biopsy (urease) | - Antigen detection in stool sample
64
How is Clostridium perfringens transmitted? Why is there no fever?
- Foodborne intoxication (ingestion of meat contaminated with toxins-potlucks) - Toxin-based
65
Are Bacillus species gram positive/negative? What shape?
Gram positive rods
66
What do Bacillus species produce?
Spores
67
What disease do Bacillus cereus heat stable enterotoxin produce? Why is there no fever?
- Emetic disease (from contaminated rice) | - Toxin-based
68
What disease do Bacillus cereus heat labile enterotoxin produce? Why is there a fever?
- Diarrheal disease | - True infection with bacterial replication
69
Are staphylococcus gram positive/negative? What shape? | How can you distinguish Staph species?
Gram positive cocci | Catalase + test
70
What temperatures can Staph species grow at?
15-40 (wide range)
71
What virulence factor do Staph species have? Is there an associated fever?
- Superantiegens (heat labile, but resistant to gastric enzymes; mainly S. aureus) - No fever

Microbiology (23 decks)

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