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Yr 2 -FHHD > M1- How bacteria causing diseases spread > Flashcards

M1- How bacteria causing diseases spread Flashcards

1
Q

what are commensals

A

healthy host colonised by bacteria that doesn’t cause disease

  • benefit from relationship w/ another organisms but host is neither benefitted/harmed
  • normal microflora
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2
Q

what is a pathogen

A

infection occurs when invading micro-organisms cause ill health

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3
Q

what are oppurtunistic pathogens

A

cause disease when opportunity arises - caused by disturbance in homeostasis between host + commensal
▹ immunocompromised host
▹ antibiotics
▹dietary imbalances (caries)

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4
Q

what is a carriage

A

person/animal asymptomatically carries pathogenic microbe to other people

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5
Q

how does normal flora help prevent infection

A

competing with pathogens for colonisation sites

▹ acts as barrier (defence mech) against colonisation + invasion by exogenous organisms

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6
Q

what is virulence

A

quantitative ability of pathogen to cause disease (measure of degree of pathogenicity)

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7
Q

What does pathogenicity of a microbe depend on

A

microbial + host factors

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8
Q

what are the microbial factors that virulence of a microbe depends on?

A
  • transmissibility
  • infectivity
  • invasiveness/toxicity
  • ability to evade host defences
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9
Q

what are the host factors that virulence of a microbe depends on?

A
  • age
  • genetic factors
  • general + local host defences
  • immunodeficiency
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10
Q

what are the 2 types of infection sources

A

exogenous

endogenous

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11
Q

what does exogenous infection source mean and 3 examples

A

coming from external source
▹ person-person contact
▹zoonosis = animal pathogens spread to humans
▹humans infected by microbes in env (soil/water)

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12
Q

what does exogenous infection source mean

A

normal flora can invade causing endogenous infection

opportunist pathogens

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13
Q

what does endemic mean

A

always present in pop at around constant level,

level can be cyclic (high in winter than summer)

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14
Q

what does epidemic mean

A

high than normal level in pop, much higher than endemic + short term
(flu)

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15
Q

what does outbreak mean

A

localised increase in incidence of disease

e.coli food poisoning

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16
Q

what does pandemic mean

A

epidemic spread between continents

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17
Q

what are the 2 general modes of transmission of infection

A

horizontal

vertical

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18
Q

what does horizontal transmission infection mode mean

A

transmission of organism between individuals

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19
Q

what does vertical transmission infection mode mean

A

transmission from mother to offspring in utero/ around birth via birth canal
(congenital syphilis) (Grp B streptococci)

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20
Q

what are congenital infections

A

vertical transmission mode of infection
▹ via mother blood + crossing placenta (rubella)
▹ can be acquired before/after delivery
(herpes, hep B)

21
Q

what are the modes of transmission of microbes

A 
▹ respiratory spread
▹ faecal-oral spread
▹ via skin or mucous membranes
▹blood
▹fomites
▹zoonoses
▹ sexual transmission
22
Q

what does fomites mean

A

inanimate object that carry microbes

23
Q

Hoe does skin to skin transfer happen

A

▹ direct contact or fomites (shared towels)

▹ transmission usually through abrasion in the epidermis (athletes foot)

24
Q

what is cellulitis

A

spread infection of soft tissues
commonly caused by streptococcus pyogenes (grp A streptococcus)
getting into small abrasion of skin

25
Q

what are signs of cellulitis

A

erythema - red, hot
oedema - swelling, pain
inflammation signs

26
Q

how does salivary spread happen

A

▹ contact with infected secretions (herpes)

▹ saliva via bite breaking through victim’s skin

27
Q

how does respiratory spread happen

A

▹ aerosolisation of secretions, depends on
- amount of infective discharge
- size of droplets
- resistance of infection to drying/ inactivation by UV light
▹ fomites (tissues)

28
Q

how does faecal-oral spread happen

A

▹ poor hygiene
▹ direct hand-mouth spread (fertiliser/contamination of food)
(salmonella/Hep A)

29
Q

how does blood borne transmission occur

A

▹ blood products/ dirty needles
(Hep B, HIV, blood transfusion)
▹ Insect host (malaria)
▹ fleas - long distance jumps

30
Q

how does zoonotic transmission occur

A

via animals where they have natural reservoirs to humans

31
Q

what is nosocomial infections + what are most common

A

hospital acquired infections
▹ urinary tract
▹wound/skin + soft tissue
▹ resp tract

32
Q

how do spores help survival of organisms

A

bacteria make spores which can survive in env for loads of years
(Bacillus anthracis)

microbe can survive in host, which then acts as a reservoir of infection of new hosts

33
Q

how easily infection spreads depends on what (6)

A
  • survival ability
  • ability to find alternative host
  • shedding capacity
  • infectivity
  • virulence
  • ability to evade immune response
34
Q

what infections are respiratory

A

influenza
measles
M.tuberculosis

35
Q

what infections are skin-contact

A

herpes

staphylococcus aureus

36
Q

what infections are faecal- oral

A

salmonella typhimurium

Hep A

37
Q

what infection are blood + body fluid

A

HIV
Hep B
syphilis

38
Q

how does attachment + invasion help spread infections

A

invading microbes must attach to host tissues by diff mechs

39
Q

how does neisseria gonorrhea spread

A

adhere to genital mucosa by fimbriae

40
Q

how does giardia laamblia spread

A

attach to jejunal mucosa by special sucking disc

41
Q

how does influenza spread

A

virus attached to host cells by its hemgluttin anitgen

42
Q

why is immune evasion important for microbes + how is it done

A
  • overcome host immune defences
    (resp bacteria secrete IgA protease-> degrades host immunoglobulin)
  • avoiding destruction by host phagocytes
    (tuberculosis mycobacterium can survive inside host macrophages)
43
Q

what is motility of a microbe

A

ability to move which likely enhances pathogenicity

flagellae

44
Q

what are the 4 ways microbe can damage the host cells

A

▹ enzymes
▹ toxins
▹ exotoxins
▹ endotoxins

45
Q

what are 2 examples of how enzymes can damage the host

A

▹ protease (porphyromonas gingivalis - perio)

▹ lipases, nucleases

46
Q

what are 2 examples of how toxins can damage the host

A 
▹ exotoxins in gram +pos bacteria 
- clostridium tetani
- corynebacterium diphtheriae
- (streptococcal erthyrogenic made by s.pyogenes -> scarlet fever(
- vibrio cholerae (cholera)
▹ endotoxins in gram -neg bacteria
47
Q

how exotoxins can damage the host

A
  • highly toxic + act at specific target sites
  • neutralised by antitoxin
  • often destroyed by heat
48
Q

how do endotoxins damage the host

A
  • endotoxins from cell wall of gram -neg bacteria (liposaccharides) -> host cells to produce IL-1 + tumour necrosis factor (TNF)
  • > fever + shock

Yr 2 -FHHD (4 decks)

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