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Medical microbiology and infectious diseases > Week 14 > Flashcards

Week 14 Flashcards

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1
Q

Define microbiota

A

Microorganisms that share our body space

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2
Q

What are the three types of microbiota?

A

Commensal
Mutualistic
Pathogenic

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3
Q

What is the microbiota also known as?

A

Flora

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4
Q

Define microbiome

A

Community of all microorganisms plus their genetic material

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5
Q

Define Bacteriotherapy

A

Therapeutic use of bacteria/ related products to treat disease

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6
Q

What type of symbiosis does human gut flora display?

A

Mutualism

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7
Q

What type of symbiosis does skin, nose and mouth flora display?

A

Commensalism

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8
Q

Define Mutualism

A

Both host and microbiota benefit

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9
Q

Define Commensalism

A

The microbiota benefits but the host is neutral (can sometimes turn into opportunistic pathogen with immunocompromised individuals)

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10
Q

What gene is the Human Microbiome Project based on?

A

16s rRNA gene

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11
Q

Define dysbiosis

A

When symbiosis is broken (pathogens may colonise and cause disease)

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12
Q

What are virulence factors?

A

The molecule or trait helping pathogens cause infections

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13
Q

What is toxigenicity?

A

The capacity of a microorganism to produce toxins

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14
Q

What gram bacteria produce endotoxins?

A

Only gram -ve

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15
Q

What gram bacteria produce exotoxins?

A

Both Gram +ve and -ve

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16
Q

What are the main kind of endotoxin?

A

Lipopolysaccharides (LPS)

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17
Q

What part of the Lipopolysaccharides (LPS) are toxic?

A

Lipid A - it activates receptors in host cells

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18
Q

What part of Lipopolysaccharides (LPS)is a target for recognition by host antibodies?

A

O antigen (repetitive glycan polymer)

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19
Q

How is the host damaged by LPS?

A
  1. the host isn’t alerted by bacterium presence
  2. lipid A is released form bacterial membrane after lysis
  3. LPS binds indirectly to CD14 and TLR4 inducing inflammation, coagulation and shock
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20
Q

Why might a lab use amoebocytes from a limulus?

A

To test for presence of endotoxins in drugs that are made from engineered bacteria

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21
Q

How could LPS help the study of anti-inflammatory drugs?

A

LPS cause inflammation, so drugs (eg. for rheumatoid arthiritis) can be tested. For example to see if there is cytokine reduction

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22
Q

Why does LPS mean that the host isn’t alerted by bacterium presence?

A

Portions of LPS are chemically similar to human cell surface membranes

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23
Q

What are the three kinds of exotoxin?

A
  1. Membrane acting
    2.Channel forming
    3.Intracellularly acting
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24
Q

How do Membrane acting exotoxins work?

A

By causing a cascade inside the cell, altering the intracellular signalling

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25
What are the two types of Membrane acting exotoxins?
a) heat stable b) Superantigens (SAgs)
26
Give three examples of heat stable toxins?
STa STb EAST1 (all to do with ETEC)
27
Describe how Superantigens (SAgs) work?
Bind to major histocompatibility (MHCs)on antigen presenting cells, and T receptors on T cells, causing excessive immune action
28
Give an example of a disease caused by a Superantigens (SAgs)
Toxic Shock Syndrome (TSS)
29
What are the two types of membrane damaging exotoxins?
Channel forming Enzymatically active toxins
30
What gram are intracellularly acting exotoxins?
Gram-ve
31
What does AB toxin stand for?
A= active toxigenic components B=receptor binding
32
Name two toxins that are AB toxins
Cholera Toxin Diptheria toxin
33
Endotoxin vs Exotoxin Which is bigger?
Endotoxin by far (x100)
34
Endotoxin vs Exotoxin Who is more toxic?
Exotoxin
35
Endotoxin vs Exotoxin Which is pyrogenic? (induces fever)
Endotoxin
36
Endotoxin vs Exotoxin Who causes Tetanus, Diptheria, Botulism?
Exotoxin
37
Endotoxin vs Exotoxin Who causes Sepsis, bacteremia?
Endotoxin
38
What kind of diseases could fecal transplant therapy help to treat?
IBS recurrent e.difficile
39
What is the 16s rRNA gene? What is it used for?
Component of 30s small subunit of prokaryotic ribosome that binds to shine dalgarno sequence. Used in taxonomy and classification
40
Bacteroides thetaiotaomicron
Commensal microbe that resides in human gut but provides no known benefit to host
41
Comorbidity
Concurrence of two or more unrelated pathologic/ disease
42
Opportunistic pathogen
Usually a commensal microbe takes advantage of your immune system being weak
43
Give some examples of Opportunistic pathogens
Strep pneumoniae Staph aureus
44
Prebiotics Vs Probiotics
Pre: non digestable food creating ideal environment for certain bacteria in gut Pro: live microorganisms
45
Define adhesion
Measurable union between bacterium and substratum that requires energy for it's reversal
46
Define substratum
Surface with receptors for adhesins
47
Define adhesin
Surface molecule capable of binding to a receptor eg. ligand
48
Invasin
Bacterial ligand that forces target cell to internalise microbe
49
What could change the host susceptibility to adhesion?
the host susceptibility relies on number of receptors, which can change as a genetic response to environment
50
What's the difference between Host specificity and tissue tropism?
Host specificity= less competition Tissue tropism= specificty within the body so even less competition
51
What's the difference between Affinity and Avidity?
Affinity= measure of binding strength at a single binding site Avidity= measure of total binding strength
52
What is Antigenic variation?
Genes recombine to make a new structure, multiple genes means various forms of adhesin
53
What is Phase variation?
Pili can be turned on and off off=capsule is antiphagocytic but stops adhesion on= turned back on for immune evasion after cell entry
54
What are OPa proteins of Neisseria?
Variable outer membrane proteins of Neisseria gonorrhoeae/ meningitidis that mediate tight interactions of pathogens and human cells
55
What kind of bacteria is Diptheria toxin produced by?
Corynebacterium diptheriae Gram +ve Actinobacteria
56
What kind of bacteria is Tetanus toxin produced by?
Clostridium Tetani gram +ve Furmicutes
57
Describe the structure of Staph. aureus
14 strand beta barrel in a mushroom like shape; forms alpha toxin pore and acts like a hemolysin
58
Give two types of enzymatically active toxins?
Phospholipase C Proteases
59
Give two examples of Phospholipase C-like toxins?
Clostridium Perfringens alpha toxins (lyses host cell) S. aureus beta hemolysin (hydrolyses plasma membrane lipids)
60
Give an example of Proteases toxins?
Porphyromonas gingivalis integrin protease (proteolyse major cell surface components)

Medical microbiology and infectious diseases (10 decks)

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