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

Gram negative bacteria Flashcards

(75 cards)

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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
What does ST bind to ?
receptor on guanylate cyclase
26
What happens when ST binds to receptor on guanylate cyclase?
stimulates production of cGMP
27
What does cGMP activate ?
cGMP-dependent protein kinase
28
Which types of E.coli have bundle forming pilli?
EHEC and EPEC
29
What does EHEC stand for?
enterohemorrhagic E.coli
30
What does EPEC stand for?
enteropathogenic E.coli
31
What do the bundle forming pilli of EHEC and EPEC allow ?
adherence to microvilli of enterocytes
32
What does T3SS stand for?
type 3 secretion system
33
Describe the Type 3 secretion system?
It is a protein appendage to inject toxins and effectors onto the cell
34
Which types of E.coli have a T3SS?
EHEC and EPEC
35
Which important receptor is injected into the enterocyte via the T3SS by EHEC and EPEC?
Tir - translocated intimin receptor
36
How does the T3SS allow bacteria to interact intimatelt with the enterocyte?
Tir is injected into the enterocyte. Intimin binds to Tir
37
In which types of E.coli do you see a rearrangement of the cytoskeleton to form pedestals?
EHEC and EPEC
38
Which type of E.coli enters the enterocyte?
EIEC
39
What does EIEC stand for?
enteroinvasive E.coli
40
Which type of E.coli produces shiga-like toxin (SLT)?
EHEC
41
What is shigellosis?
infection with shigella
42
What is shigellosis characterised by?
bloody diarrhoea
43
Is shigellosis self-limiting?
usually self-limiting in adults
44
Why does shigella have a low infective dose?
acid tolerant
45
Describe the infective dose of shigella ?
low
46
What does M cells stand for?
microfold cells
47
What are M cells?
antigen sampling cells that overlie immune cells
48
Describe the pathogenesis of shigella
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
What type of cell takes up the shigella after it has been taken up by the M cell ?
macrophage
50
What toxin does Shigella produce that blocks protein synthesis ?
the shiga toxin
51
What is a possible complication of shigellosis?
hemolytic uremic syndrome (HUS)
52
What is hemolytic uremic syndrome ?
microvascular thrombosis in the kidneys- can cause kidney failure
53
Which species of salmonella is responsible for salmonellosis ?
Salmonella enterica
54
What are the three forms of salmonellosis caused by Salmonella emterica?
Gastroenteritis/ enterocolitis Enteric fever Bateraemia
55
What is enteric fever also known as ?
Typhoid
56
Which Salmonella enterica serovars cause gastroenteritis ?
Enteritidis and Typhimurium
57
Which Salmonella enterica serovars cause enteric fever ?
Typhi and Paratyphi
58
Describe the pathogensis of salmonellosis ?
Congestion of contaminated food/water invasion of gut epithelium Enters submucosal macrophages Intracellular survival/ replication
59
Which Salmonella enterica serovar produces the typhoid toxin?
Typhi
60
Describe how Salmonella enterica causes gastroenteritis
1. bacterial-mediated endocytosis 2. Inducing chemokine release 3. Neutrophil recruitment and migration 4. Neutrophil induced tissue injury 5. Fluid and electrolyte loss
61
Describe how Salmonella enterica causes enteric fever?
1. Bacterial-mediated endocytosis 2. Transcytosis 3. Survival in macrophage then systemic spread via lymphatics and blood
62
Which bacteria is responsible for 30% of UTIs?
Proteus mirabilis
63
What is the major virulence factor of Proteus mirabilis?
urease
64
Urease is the major virulence factor of Proteus mirabilis. How does urease cause kidney stones?
hydrolyses urea to generate ammonia | ammonia increases the pH of the urine
65
What can Proteus mirabilis differentiate into?
an elongated, hyperflagellated form
66
What does nosocomial mean?
originating in hospital
67
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?
Klebsiella pneumoniae
68
Which species of bacteria causes cholera?
vibrio cholerae
69
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
Vibrio cholerae
70
Which bacteria causes voluminous watery stools and has a 50-60% mortality if untreated?
Vibrio cholerae
71
How is cholera treated?
Oral rehydration therapy
72
How does cholera cause diarrhoea?
``` Via the cholera toxin This locks the G protein in the on state Increased cAMP production cAMP activates protein kinase CFTR activity increased ```
73
What acute infections can pseudomonas auruginosa cause?
localised infections such as burns/surgical wounds, UTIs and keratitis Systemic infection- sepsis Nosocomial pneumonia in patients on ventilators
74
Which pathogen is a chronic infection in those with cystic fibrosis ?
Pseudomonas aeruginosa
75
Why is Pseudomonas aeruginosa difficult to treat?
multiple antibiotic resistance

Phase 2a Introduction to clinical sciences (8 decks)

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