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Phase 2a Introduction to clinical sciences > Gram negative bacteria > Flashcards

Gram negative bacteria Flashcards

1
Q

Which has the thicker layer of peptidoglycan out of gram negative and gram positive bacteria?

A

gram positive

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2
Q

Which membrane of a gram negative bacteria is the cytoplasmic membrane (inner or outer)

A

inner

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3
Q

What does LPS stand for? What can it also be called?

A

lipopolysaccharide AKA endotoxin

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4
Q

Where do you find LPS?

A

The outer membrane of gram negative bacteria

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5
Q

Which part of LPS is responsible for its toxic properties?

A

lipid A

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6
Q

What are the components of LPS?

A

Lipid A
Core (R) antigen
Somatic (O) antigen

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7
Q

What are virulence factors?

A

any products or strategies that contribute to pathogenicity/ virulence

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8
Q

Which family are Shigella flexneri, Eschericha coli and Salmonella enterica members of ?

A

Enterobacteraceae

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9
Q

Out of Shigella flexneri, Escherichia coli and Salmonella enterica, which can use lactose?

A

Escherichia coli

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10
Q

What is the end product when a bacteria ferments lactose?

A

lactic acid

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11
Q

Why would a colony appear red on MacConkey-lactose agar?

A

production of lactic acid lowers the pH

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12
Q

Do Shigella have flagella?

A

no

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13
Q

Which out of salmonella and shigella is motile?

A

salmonella

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14
Q

What is a serovar/serotype?

A

a distinct variation within a species of bacteria or virus

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15
Q

What type of antigens are the K antigens of E.coli?

A

capsular antigens

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16
Q

Which letter antigen is the flagellar antigen?

A

H

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17
Q

What does E.coli stand for?

A

Escherichia coli

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18
Q

What types of infection can be caused by Escherichia coli?

A

wound infections, UTIs, gastroenteritis, traveller’s diarrhoea, bacteraemia and meningitis (rare in UK)

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19
Q

What is the most common cause of traveller’s diarrhoea ?

A

ETEC (enterotoxic Echerichia coli)

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20
Q

What is bacteraemia?

A

when bacteria get into the blood

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21
Q

What are the pathogenicity determinants of ETEC?

A

heat labile toxin (LT) and heat stable toxin (ST)

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22
Q

Describe the mechanism by which the LT secreted by ETEC causes diarrhoea ?

A

LT is taken up by the enterocyte and locks the G- protein in the on state
This stimulates adenylate cyclase to produce cAMP
cAMP binds to protein kinase A. PKA is activated
PKA activates CFTR
CFTR transports Cl- and water out of the cell

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23
Q

Describe the mechanism by which ST secreted by ETEC causes diarrhoea ?

A

Binds to receptor on guanylate cyclase
stimulates guanylate cyclase to produce cGMP
cGMP activates cGMP-dependent protein kinase (cGKII)
this activates CFTR

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24
Q

Which toxin secreted by ETEC mimics guanylin?

A

ST

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25
Q

What does ST bind to ?

A

receptor on guanylate cyclase

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26
Q

What happens when ST binds to receptor on guanylate cyclase?

A

stimulates production of cGMP

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27
Q

What does cGMP activate ?

A

cGMP-dependent protein kinase

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28
Q

Which types of E.coli have bundle forming pilli?

A

EHEC and EPEC

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29
Q

What does EHEC stand for?

A

enterohemorrhagic E.coli

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30
Q

What does EPEC stand for?

A

enteropathogenic E.coli

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31
Q

What do the bundle forming pilli of EHEC and EPEC allow ?

A

adherence to microvilli of enterocytes

32
Q

What does T3SS stand for?

A

type 3 secretion system

33
Q

Describe the Type 3 secretion system?

A

It is a protein appendage to inject toxins and effectors onto the cell

34
Q

Which types of E.coli have a T3SS?

A

EHEC and EPEC

35
Q

Which important receptor is injected into the enterocyte via the T3SS by EHEC and EPEC?

A

Tir - translocated intimin receptor

36
Q

How does the T3SS allow bacteria to interact intimatelt with the enterocyte?

A

Tir is injected into the enterocyte. Intimin binds to Tir

37
Q

In which types of E.coli do you see a rearrangement of the cytoskeleton to form pedestals?

A

EHEC and EPEC

38
Q

Which type of E.coli enters the enterocyte?

39
Q

What does EIEC stand for?

A

enteroinvasive E.coli

40
Q

Which type of E.coli produces shiga-like toxin (SLT)?

41
Q

What is shigellosis?

A

infection with shigella

42
Q

What is shigellosis characterised by?

A

bloody diarrhoea

43
Q

Is shigellosis self-limiting?

A

usually self-limiting in adults

44
Q

Why does shigella have a low infective dose?

A

acid tolerant

45
Q

Describe the infective dose of shigella ?

46
Q

What does M cells stand for?

A

microfold cells

47
Q

What are M cells?

A

antigen sampling cells that overlie immune cells

48
Q

Describe the pathogenesis of shigella

A

Taken up by M cells
Translocate to the basolateral side of the cell
Taken up by a macrophage
Induce apoptosis of the macrophage
Released from the macrophage and invade adjacent cells
Movement of shigella from cell to cell damages the epithelium
Apoptotic macrophage releases cytokines, causing inflammation

49
Q

What type of cell takes up the shigella after it has been taken up by the M cell ?

A

macrophage

50
Q

What toxin does Shigella produce that blocks protein synthesis ?

A

the shiga toxin

51
Q

What is a possible complication of shigellosis?

A

hemolytic uremic syndrome (HUS)

52
Q

What is hemolytic uremic syndrome ?

A

microvascular thrombosis in the kidneys- can cause kidney failure

53
Q

Which species of salmonella is responsible for salmonellosis ?

A

Salmonella enterica

54
Q

What are the three forms of salmonellosis caused by Salmonella emterica?

A

Gastroenteritis/ enterocolitis
Enteric fever
Bateraemia

55
Q

What is enteric fever also known as ?

56
Q

Which Salmonella enterica serovars cause gastroenteritis ?

A

Enteritidis and Typhimurium

57
Q

Which Salmonella enterica serovars cause enteric fever ?

A

Typhi and Paratyphi

58
Q

Describe the pathogensis of salmonellosis ?

A

Congestion of contaminated food/water
invasion of gut epithelium
Enters submucosal macrophages
Intracellular survival/ replication

59
Q

Which Salmonella enterica serovar produces the typhoid toxin?

60
Q

Describe how Salmonella enterica causes gastroenteritis

A
  1. bacterial-mediated endocytosis
  2. Inducing chemokine release
  3. Neutrophil recruitment and migration
  4. Neutrophil induced tissue injury
  5. Fluid and electrolyte loss
61
Q

Describe how Salmonella enterica causes enteric fever?

A
  1. Bacterial-mediated endocytosis
  2. Transcytosis
  3. Survival in macrophage then systemic spread via lymphatics and blood
62
Q

Which bacteria is responsible for 30% of UTIs?

A

Proteus mirabilis

63
Q

What is the major virulence factor of Proteus mirabilis?

64
Q

Urease is the major virulence factor of Proteus mirabilis. How does urease cause kidney stones?

A

hydrolyses urea to generate ammonia

ammonia increases the pH of the urine

65
Q

What can Proteus mirabilis differentiate into?

A

an elongated, hyperflagellated form

66
Q

What does nosocomial mean?

A

originating in hospital

67
Q

Which bacteria can cause opportunistic nosocomial infections, is normally found in the GI tract and sometimes the oropharynx and can lead to infections such as UTI, pneumonia, surgical wound infections and sepsis?

A

Klebsiella pneumoniae

68
Q

Which species of bacteria causes cholera?

A

vibrio cholerae

69
Q

Which bacteria looks like curved rods, has a single flagellum and is ingested by shellfish or contamination of drinking water? Infection can lead to dehydration and death

A

Vibrio cholerae

70
Q

Which bacteria causes voluminous watery stools and has a 50-60% mortality if untreated?

A

Vibrio cholerae

71
Q

How is cholera treated?

A

Oral rehydration therapy

72
Q

How does cholera cause diarrhoea?

A 
Via the cholera toxin
This locks the G protein in the on state 
Increased cAMP production 
cAMP activates protein kinase 
CFTR activity increased
73
Q

What acute infections can pseudomonas auruginosa cause?

A

localised infections such as burns/surgical wounds, UTIs and keratitis
Systemic infection- sepsis
Nosocomial pneumonia in patients on ventilators

74
Q

Which pathogen is a chronic infection in those with cystic fibrosis ?

A

Pseudomonas aeruginosa

75
Q

Why is Pseudomonas aeruginosa difficult to treat?

A

multiple antibiotic resistance

Phase 2a Introduction to clinical sciences (8 decks)

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