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human structure and function > microbes and infection > Flashcards

microbes and infection Flashcards

1
Q

what are the different types of microbes?

A
  • bacteria
  • fungi
  • viruses
  • algae
  • protozoa
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2
Q

what are the two names of microbes?

A

genus and species name

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3
Q

how big are bacteria?

A

very small 1-5um

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4
Q

what are the three basic shapes of bacteria?

A
  • rod: bacilli
  • spherical: cocci
  • spiral: sprillus
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5
Q

what glycoprotein does the cell wall of bacteria incorporate?

A

peptidoglycan

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6
Q

do bacteria contain a nucleus?

A

no

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7
Q

does bacteria contain membrane-bound organelles?

A

no

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8
Q

how does bacteria reproduce?

A

binary fission

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9
Q

how big is a virus?

A

very small 20nm-100nm

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10
Q

what is an obligate parasite?

A

it can only reproduce inside the host cell

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11
Q

what is a naked virus?

A

genetic material is surrounded by a protein coat (capsid)

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12
Q

what is an enveloped virus?

A

naked virus plus an outer membrane or envelope- derived from the plasma membrane of the previous host cell

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13
Q

what are the four steps of typical viral infection (lytic)?

A
  1. attachment
  2. penetration
  3. replication
  4. maturation and release
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14
Q

how do naked viruses penetrate the target cell?

A

engulf (endocytosis)

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15
Q

how do enveloped viruses penetrate the target cell?

A

fuse with the host cell membrane

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16
Q

how do naked viruses mature and release from the target cell?

A

trigger lysis of host cell > viral exit kills cell

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17
Q

how do enveloped viruses mature and release from the target cell?

A

bud from the host cell, taking part of the cell membrane as an envelope > usually kills the host cell

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18
Q

what are fungi?

A

eukaryotic cell with cell wall containing chitin

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19
Q

what do fungi feed on?

A

organic matter

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20
Q

what is a symbiotic relationship?

A

2 organisms living together

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21
Q

what are the three classes of microbes humans interact with?

A
  • normal flora
  • transient microbes
  • pathogens
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22
Q

what are the three types of relationships possible between microbes and humans?

A
  • commensalism
  • mutualism
  • parasitism
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23
Q

what is commensalism?

A

one partner benefits the other is unaffected

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24
Q

what is mutualism?

A

both partners benefit

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25
Q

what is parasitism?

A

one partner benefits at the expense of another

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26
Q

what is colonisation?

A

establishment and growth on a body surface

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27
Q

what are transient microbes?

A

temporary and remain on the body for a short time

28
Q

why are transient microbes unable to colonise on body surfaces?

A
  • can not compete with normal flora for living space and nutrients
  • eliminated by bodies defences
  • dislodged by human activity
29
Q

what is infection?

A

invasion of the body by a pathogenic microbe

30
Q

what is a pathogen as a microbe?

A

microbes that can cause an infectious disease

31
Q

what is an infectious disease?

A

disorder of a structure or function due to damage caused by microbe

32
Q

is infectious disease always transmissible?

A

no

33
Q

what is virulence?

A

capacity of the pathogen to cause disease

34
Q

what are some factors that can increase the chances of an infection occurring?

A

host susceptibility and conducive enviros

35
Q

what are factors that increase a host’s susceptibility to infection?

A
  • pre-existing poor health
  • poor immune status
  • immunodeficiency
  • compromised barriers
  • extremes of age
36
Q

what are some enviro conditions that affect the conducive enviro for infection?

A
  • health status
  • reservoir of infection
  • ease of pathogen transmission between hosts
37
Q

what are some conducive enviro for infection?

A

poverty, famine, natural disasters, and conflict

38
Q

what is an opportunistic pathogen?

A

microbe that doesn’t normally cause disease but can do so under certain circumstances

39
Q

when can microbes of the normal flora cause opportunistic infection?

A
  • ecological balance of normal flora is upset
  • microbes are relocated
  • host innate and/or adaptive defences are compromised
40
Q

what are the steps a pathogen must take while evading host defences?

A
  • entry to body and attach to target cells
  • multiplication in body using host resources
  • damage body
  • shedding or exit from body in large numbers to ensure transmission to next host
41
Q

what is a portal of entry for a pathogen?

A

the site at which a pathogen enters the body

42
Q

what are some portals of entry?

A

skin and mucous membranes

43
Q

what are some entry points for pathogens through the skin?

A
  • hair follicles, sweat glands
  • some can live in or bore through skin
  • compromised barriers
44
Q

what are some entry points for pathogens through the mucous membranes?

A
  • respiratory tract
  • gastrointestinal tract
  • urinary
  • reproductive
  • conjunctiva of eyes
45
Q

what is the most common portal of entry for pathogens?

A

respiratory tract

46
Q

how do pathogens attach to establish an infection?

A
  • must attach, many have adhesions on their surface so they can bind to surface receptors
  • some bacteria secrete sticky glycocalyx that cements them
  • many viruses adhere to specific molecules
47
Q

what is the incubation period of an infectious disease?

A

the time during which the pathogen is overcoming early host defences and utilising host resources to multiply to a critical population size

48
Q

what are extracellular pathogens?

A

majority of bacteria and fungi obtain nutrients from ECF

49
Q

what are intracellular pathogens?

A

all viruses, some bacteria, and fungi obtain nutrients from within cells

50
Q

what do the strategies or virulence factors for overcoming defences for invading pathogens include?

A
  • overcoming innate defences such as surface barriers and phagocytes
  • overcoming adaptive defences such as degrading antibodies and antigenic variation
51
Q

how do some pathogens overcome surface barriers?

A

release enzymes that breakdown epithelial/connective tissue to invade deeper tissue

52
Q

how do some bacteria resist phagocytes?

A
  • have slippery capsules that prevent phagocytes adhering and engulfing
  • some release toxins that kill phagocytes or release enzymes that inactivate digestive enzymes
53
Q

what are some toxins that are released by some bacteria that kill phagocytes or inactivate digestive enzymes?

A
  • leukocidin: kills neutrophils

- catalase: destroys lysosomal enzymes

54
Q

what are some enzymes that are produced by pathogens that can destroy antibodies?

A

IgA proteases destory IgA antibodies in mucus at mucosal surfaces

55
Q

how can damage to the host be directly caused by a pathogen?

A
  • damage caused by enzymes or toxins
  • cytopathic effects
  • use of host as food source
56
Q

how can damage to the host be indirectly caused by a pathogen?

A
  • inflammation: swelling, phagocytic enzymes, complement, scarring
  • antibodies and cytotoxic cells
57
Q

how can enzymes released by a pathogen cause damage?

A

tissue damage

58
Q

how can toxins released by a pathogen cause damage?

A
  • fever
  • cardiovascular and nervous system disturbances
  • shock
  • diarrhoea
  • death
59
Q

how can cytopathic effects of pathogens induce damage?

A

microbes activity causes damage and kills host cells

60
Q

what are portals of exit for pathogens?

A

when pathogen leaves the body to spread to a new host

61
Q

what are the most common forms of portals of exit for pathogens?

A

respiratory and digestive tract pathogen

62
Q

what is chronic infection?

A

is not completely eliminated and continues to multiply slowly and cause increasing amounts of damage

63
Q

what is a latent infection?

A

pathogen persists lifelong but does not multiply or cause damage and can be reactivated

64
Q

is an acute infection short or long term?

A

short

65
Q

when is an acute infection transmissible?

A

during incubation, prodromal, disease or recovery period

66
Q

when can latent infections be transmitted?

A

cannot when not multiplying

67
Q

when can chronic infections be transmitted?

A

always

human structure and function (21 decks)

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