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micr3330 > Practice questions > Flashcards

Practice questions Flashcards

1
Q

T3SS of yersinia

A
  • Present in all three pathogenic Yersinia species
  • Encoded on the pCD1 plasmid
  • Expression activated by temperature change to 37ºC and presence of calcium
  • Inject multiple toxic yersinia effector proteins (Yops) directly into host cells
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2
Q

Three pathogenic Yersinia species

A
  • Y. enterocolitica
  • Y. pseudotuberculosis
  • Y. pestis
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3
Q

Structure of T3SS

A
  • Injectisome
  • Needle fixed into the bacterial inner and outer membrane and protrudes from the surface to penetrate host membrane
  • Translocon forms a channel through host membrane
  • Yop effectors transferred from the cytoplasm into the host cell
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4
Q

What does Yop stand for

A

Yersinia outer proteins

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5
Q

Examples of Yops

A
  • YopE
  • YopH
  • YopM
  • YopT
  • YpkA/YopO
  • YopP/YopJ
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6
Q

YopE

A

Disrupts cytoskeleton

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7
Q

YopH

A

Disrupts focal adhesions

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8
Q

YopM

A

Regulation of host cell necrosis

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9
Q

YpkA/YopO

A

Rounding up of cells

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10
Q

YopP/YopJ

A

Apoptosis of macrophages

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11
Q

TopT

A

Disrupts actin filaments

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12
Q

Functions of Yops

A
  • To subvert host cell signalling pathway
  • Trigger apoptosis or cell death
  • Inhibit phagocytosis
  • Suppress immune cells
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13
Q

DRAW T3SS

A

DRAW T3SS

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14
Q

Virulence factors Yersinia pestis

A
  • Plasminogen activator
  • Murine toxin
  • F1 Capsular antigen
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15
Q

Virulence plasmids in Yersinia

A
  • pPCP1
  • pMT1
  • pCD1
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16
Q

Virulence factor that pPCP1 encodes

A
  • Plasminogen activator
  • Pla protease
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17
Q

Virulence factor that pMT1 encodes

A
  • Murine toxin
  • F1 capsular antigen
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18
Q

Virulence factor that pCD1 encodes

A
  • Low Calcium Response (Lcr) T3SS
  • Yops
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19
Q

Plasminogen activator virulence factor

A
  • Transmembrane protease
  • Encoded on plasmid pPCP1
  • Has protease activity that interacts and cleaves host proteins targets
  • Targets important in response to infection (e.g. coagulation and fibrin clot)
  • Allows bacteria to disseminate from bite site and subversion of immune response
20
Q

Yersinia murine toxin (Ymt) virulence factor

A
  • Phospholipase D (PLD) activity
  • Encoded by plasmid pMT1
  • Required for survival in midgut of rat flea
  • Intracellular PLD activity protects Y.pestis from a cytotoxic digestion product of blood plasma in the flea gut.
  • Enables colonisation of the flea midgut
  • Acquisition of PLD precipitated the
    transition of Y. pestis to obligate arthropod-borne transmission
21
Q

Low calcium response V (LcrV)

A
  • Mutants deficient in LcrV not cytotoxic
  • Lack of LcrV leads to secretion of effectors into the extracellular environment
  • Several virulence roles proposed for V antigen
  • LcrV or V antigen confers resistance to
    phagocytosis
22
Q

Several virulence roles proposed for V antigen

A
  • Regulation of T3SS
  • Translocator (part of the secretion apparatus)
  • Immune modulator
23
Q

F1 Capsular Antigen

A
  • Encoded by plasmid pMT1 (pFra)
  • Forms a surface located polypeptide capsule at 37°C growth
  • Characteristic capsule visible by light microscopy
  • Antiphagocytic activity
  • Is antigenic and a good vaccine candidate
  • Important but not essential for virulence
24
Q

5 Virulence factors of Pseudomonas aeruginosa

A
  1. Type IV pili
  2. Exopolysaccharides
  3. Exotoxin A
  4. T3SS
  5. Antioxidant enzymes
25
Q

Type IV in P. aeruginosa

A
  • Retractile appendages
  • Crucial for the initiation of infection by
    controlling twitching motility and attachment to host cells
26
Q

Exopolysaccharides in P. aeruginosa

A
  • Alginate, Psl and Pse
  • Contribute to biofilm matrix
  • Impair bacterial clearance
  • Promote establishment of chronic infections
27
Q

T3SS in P. aeruginosa

A

Critical for the destruction of host defences through the injection of four
cytotoxic effectors

28
Q

4 Cytotoxic effectors secreted by T3SS in P. aeruginosa

A

ExoU, ExoT, ExoS and ExoY

29
Q

Exotoxin A (ETA) in P. aeruginosa

A
  • Most toxic product released by P. aeruginosa
  • Inhibits host protein synthesis due to ADP-ribosylating activity
30
Q

Antioxidant enzymes in P. aeruginosa

A
  • Help overcome oxidative stress in host
  • Includes catalases KatA, KatB and KatE
31
Q

Additive

A
  • Result of two drugs is equal to the combined action of each of the drugs used separately
  • Isobologram is straight line
32
Q

Synergistic

A
  • Result of the two drugs is significantly better than additive
  • Isobologram curves down
33
Q

Antagonistic

A
  • Result of the two drugs is significantly less than additive
  • Isobologram curves up
34
Q

Pathophysiology of TB (what are the possible outcomes after exposure to respiratory droplets containing Mycobacterium tuberculosis)

A
  1. Initial infection
  2. Innate immune phase
  3. Adaptive immune phase
35
Q

Initial infection of TB

A
  • Droplet nuclei inhaled (can contain 1-3 bacilli, and remain airborne from minutes to hours)
  • After inhalation, droplet nuclei can reach the alveolar membrane
36
Q

Innate immune phase of TB

A
  • Bacilli phagocytosed by alveolar macrophages
  • Most are contained or destroyed
  • Some survive phagocytosis by blocking lysosome fusion with phagosome (replicate in macrophages, released when macrophages die)
  • Macrophages stimulated and produce proinflammatory cytokines and chemokines (drives recruitment of more leukocytes to the site of infection)
  • Bacilli grow until threshold number of organisms is reached 2-8 weeks after infection
  • No immediate host response as no toxin produced
37
Q

Major cells types involved in innate immune phase

A

Macrophages, neutrophils, dendritic & natural killer cells

38
Q

Adaptive immune phase in TB

A
  • Bacteria released from macrophages travel to lymph nodes and present to lymphocytes
  • Stimulates cell mediated immunity
39
Q

Cell mediated immunity in TB

A
  • Recruitment and activation of T lymphocytes
  • Release of lymphokines, monokines and cytokines by T cells
40
Q

Effects of the release of lymphokines, monokines and cytokines by T cells

A
  • Promotes recruitment of cells to infection site
  • Activates macrophages to kill bacilli
  • Triggers formation of early granuloma
  • Macrophages fuse to form multi nucleated giant cells or differentiate into foamy cells and surround the granuloma
41
Q

TB granuloma

A
  • Caseating (necrotic) core
  • B and T cells form outer layer
  • Epithelial macrophage, macrophage, DCs, NK cells, neutrophils and giant cells form middle layer
  • Mycobacterium tuberculosis, apoptotic infected macrophage and apoptotic infection epithelial macrophage form inner layer
42
Q

It is estimated one quarter of the world has latent TB, has this changed from previous estimates and what is latent TB

A
  • Yes, previous estimate was one third, has become lower
  • Latent TB describes people that are infected but NOT sick. They cannot transmit the disease
43
Q

Spread plate method viable organisms per mL in an original culture calculation

A

Cfu = number of colonies/volume plated in mL x dilution factor

44
Q

Helber chamber total number of cells per ml in the original culture calculation

A

Number of cells per square / volume of square

45
Q

Frequency of transformation calculation

A

number of colonies x (broth/plated amount) x fraction of ligation mix x 1000/1000

46
Q
A

micr3330 (29 decks)

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