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Y3- I & W > microbiology how bacteria cause disease > Flashcards

microbiology how bacteria cause disease Flashcards

1
Q

define pathogen

A

an organism that is capable of causing the host damage or disease

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2
Q

define opportunistic pathogen

A

an organism that is a member of the resident microbiota or normally inhabiting the external environment that causes infection under certain circumstances

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3
Q

define symbiont

A

a member of the resident microbiota that confers benefit to the host

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4
Q

define pathobiont

A

a member of the resident microbiota which confers damage to the host

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5
Q

define dysbiosis

A

imbalances in the resident human microbiota or our responses to them

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6
Q

describe pathogenicity

A

the degree of virulence of a microbe to cause damage in the host

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7
Q

define virulence

A

relative capacity of the organism to cause damage in the host

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8
Q

define virulence determinant factor

A

component of the pathogen that damages the host

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9
Q

define lethal dose

A

LD50 is the number of pathogens required to kill 50% of the host

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10
Q

what is the major steps of virulence mechanisms

A

• Transmission
• Adherence to host surfaces
• Invasiveness
Toxigenicity

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11
Q

describe transmission

A 
infections can be acquired by an internal or external sources 
eg ingestion 
inhalation 
trauma 
needle stick
sexual transmission
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12
Q

what are the four portals of entry for transmission

A

skin
resp tract
GU tract
GI tract

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13
Q

describe adherence to host surfaces

A

some fungi and bacteria produce substances that help with adherence
critical for colonisation

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14
Q

give examples of bacteria requiring adherence to host surfaces

A

N gonorrhoea and E coli with pili

S mutans- Extracellular polysaccharide layer helps it adhere

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15
Q

what is quorum sensing

A

molecules(homoserine lactone) are secreted by bacteria in biofilm
It is a cell-cell communication which allows bacteria to share information about cell density and adjust gene expression accordingly
May lead to reduction in metabolic activity or other genes being expressed

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16
Q

describe invasiveness

A

It is important and depends on bacterial enzymes
Eg collagenase and hyaluronidase
Allows for the breakdown of intercellular structures and allows for bacteria to enter straight easily though tissues

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17
Q

where is hyaluronidase present

A

in S aureus and S pyogenes

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18
Q

where is collagenase present

A

present in clostridium perfringens

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19
Q

what does a clot inhibit

A

phagocytosis and immune responsee has no access

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20
Q

how do coagulase and kinase work together

A

→ The bacteria produce coagulase
→ The clot forms inhibits phagocytosis, immune response has no access, antibiotics are not effective
The bacteria later produce kinase which dissolves the clot and releases bacteria

21
Q

describe immunoglobulin protease

A

degrades IgA on mucosal surface and allows bacteria to adhere

22
Q

what are leukocidins

A

they can destroy immune host cells such as neutrophilic leukocytes and macrophages

23
Q

describe toxigenicity

A

two types of toxic
endotoxins
exotoxins

24
Q

what are endotoxins

A

are the lipid portions of the LPS that are part of the outer cell wall of the gram -ve bacteria

25
Q

what are the biological effects of endotoxins

A

→ Fever- release of IL-1 from macrophages
→ Hypotension, shock and perfusion of major organs- due to vasodilation
→ Inflammation
→ Tissue ischaemia
→ Increased phagocytic activity of macrophages
Increased antibody production

26
Q

why do the biological effects of endotoxins occur

A

due to the host factors producing IL-1 and TNF from macrophages

27
Q

what can occur in +ve bacteria

A

endotoxin like effects- occur from trichroic acid or peptidoglycan which can release TNF and iL-1

28
Q

describe exotoxins

A

Produced by both gram +ve and gram -ve bacteria
Mostly by gram +ve though
Secreted and released into the environment via lysis

29
Q

give examples of neurotoxins

A

Tetanus, diphtheria and botulinum toxins are neurotoxins

30
Q

how do exotoxins cause disease

A

they can cause disease to a distant part of the body due to the exotoxin diffusing

31
Q

what does the tetanus toxin cause

A

locked jaw or masseter muscle spasm

32
Q

what does tentanospasmin cause muscle spasms

A

prevented the release of inhibitory neurotransmitter glycine which causes muscle spasms

33
Q

describe the botulinum toxin

A

one of the most toxic compounds

34
Q

how does the botulinum toxin work

A

The toxin blocks the release of acetylcholine at the synapse and leads to paralysis of the muscles
○ It is an obligate anaerobe and endospore former( may transform into a spore in harsh environments to protect itself)

35
Q

what are the symptoms of botulism

A 
→ 1-2 days after ingestion 
	→ Descending motor loss with flaccid paralysis 
	→ Diplopia 
	→ Dysphagia 
	→ Speech problems 
	→ Dry mouth
	→ Resp failure 
	→ Death
36
Q

what is the bacterium that causes cholera and its endotoxin

A

vibrio cholerae

endotoxin is enterotoxin

37
Q

what is the bacterium that causes diphtheria

A

corynebacterium diphtheriae

38
Q

what is the bacterium that causes diarrhoea, pseudomembranous colitis

A

c difficile

39
Q

what is the bacterium that causes haemorrhage colitis and its endotoxin

A

e coli O157

endotoxin is verotoxin

40
Q

what is the bacterium that causes whooping cough and its endotoxin

A

bordetella pertussis

pertussis toxin

41
Q

what is the bacterium that causes scarlet fever

A

strep pyogenes

exotoxins

42
Q

what is the bacterium that causes scaled skin syndrome and the endotoxin

A

s aureus

endotoxin - epidermolysin

43
Q

what are bacterial virulence factors

A 
adhesin
invasin 
impedin 
modulin 
aggresin
44
Q

what is adhesin

A

enables binding to host tissue

45
Q

what is invasin

A

enables invasion of host cell/tissue

46
Q

what is impedin

A

enables avoidance of host defence mechanism(s)

47
Q

what is aggresin

A

causes direct damage to host

48
Q

what is modulin

A

induces indirect damage by perturbing regulation of host defences

Y3- I & W (21 decks)

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