microbes and infection

Question 1

what are the different types of microbes?

Answer 1

• bacteria
• fungi
• viruses
• algae
• protozoa

Question 2

what are the two names of microbes?

Answer 2

genus and species name

Question 3

how big are bacteria?

Answer 3

very small 1-5um

Question 4

what are the three basic shapes of bacteria?

Answer 4

• rod: bacilli
• spherical: cocci
• spiral: sprillus

Question 5

what glycoprotein does the cell wall of bacteria incorporate?

Answer 5

peptidoglycan

Question 6

do bacteria contain a nucleus?

Answer 6

no

Question 7

does bacteria contain membrane-bound organelles?

Answer 7

no

Question 8

how does bacteria reproduce?

Answer 8

binary fission

Question 9

how big is a virus?

Answer 9

very small 20nm-100nm

Question 10

what is an obligate parasite?

Answer 10

it can only reproduce inside the host cell

Question 11

what is a naked virus?

Answer 11

genetic material is surrounded by a protein coat (capsid)

Question 12

what is an enveloped virus?

Answer 12

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

Question 13

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

Answer 13

1. attachment
2. penetration
3. replication
4. maturation and release

Question 14

how do naked viruses penetrate the target cell?

Answer 14

engulf (endocytosis)

Question 15

how do enveloped viruses penetrate the target cell?

Answer 15

fuse with the host cell membrane

Question 16

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

Answer 16

trigger lysis of host cell > viral exit kills cell

Question 17

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

Answer 17

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

Question 18

what are fungi?

Answer 18

eukaryotic cell with cell wall containing chitin

Question 19

what do fungi feed on?

Answer 19

organic matter

Question 20

what is a symbiotic relationship?

Answer 20

2 organisms living together

Question 21

what are the three classes of microbes humans interact with?

Answer 21

• normal flora
• transient microbes
• pathogens

Question 22

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

Answer 22

• commensalism
• mutualism
• parasitism

Question 23

what is commensalism?

Answer 23

one partner benefits the other is unaffected

Question 24

what is mutualism?

Answer 24

both partners benefit

Question 25

what is parasitism?

Answer 25

one partner benefits at the expense of another

Question 26

what is colonisation?

Answer 26

establishment and growth on a body surface

Question 27

what are transient microbes?

Answer 27

temporary and remain on the body for a short time

Question 28

why are transient microbes unable to colonise on body surfaces?

Answer 28

- can not compete with normal flora for living space and nutrients - eliminated by bodies defences - dislodged by human activity

Question 29

what is infection?

Answer 29

invasion of the body by a pathogenic microbe

Question 30

what is a pathogen as a microbe?

Answer 30

microbes that can cause an infectious disease

Question 31

what is an infectious disease?

Answer 31

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

Question 32

is infectious disease always transmissible?

Answer 32

no

Question 33

what is virulence?

Answer 33

capacity of the pathogen to cause disease

Question 34

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

Answer 34

host susceptibility and conducive enviros

Question 35

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

Answer 35

- pre-existing poor health - poor immune status - immunodeficiency - compromised barriers - extremes of age

Question 36

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

Answer 36

- health status - reservoir of infection - ease of pathogen transmission between hosts

Question 37

what are some conducive enviro for infection?

Answer 37

poverty, famine, natural disasters, and conflict

Question 38

what is an opportunistic pathogen?

Answer 38

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

Question 39

when can microbes of the normal flora cause opportunistic infection?

Answer 39

- ecological balance of normal flora is upset - microbes are relocated - host innate and/or adaptive defences are compromised

Question 40

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

Answer 40

- 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

Question 41

what is a portal of entry for a pathogen?

Answer 41

the site at which a pathogen enters the body

Question 42

what are some portals of entry?

Answer 42

skin and mucous membranes

Question 43

what are some entry points for pathogens through the skin?

Answer 43

- hair follicles, sweat glands - some can live in or bore through skin - compromised barriers

Question 44

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

Answer 44

- respiratory tract - gastrointestinal tract - urinary - reproductive - conjunctiva of eyes

Question 45

what is the most common portal of entry for pathogens?

Answer 45

respiratory tract

Question 46

how do pathogens attach to establish an infection?

Answer 46

- 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

Question 47

what is the incubation period of an infectious disease?

Answer 47

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

Question 48

what are extracellular pathogens?

Answer 48

majority of bacteria and fungi obtain nutrients from ECF

Question 49

what are intracellular pathogens?

Answer 49

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

Question 50

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

Answer 50

- overcoming innate defences such as surface barriers and phagocytes - overcoming adaptive defences such as degrading antibodies and antigenic variation

Question 51

how do some pathogens overcome surface barriers?

Answer 51

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

Question 52

how do some bacteria resist phagocytes?

Answer 52

- have slippery capsules that prevent phagocytes adhering and engulfing - some release toxins that kill phagocytes or release enzymes that inactivate digestive enzymes

Question 53

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

Answer 53

- leukocidin: kills neutrophils | - catalase: destroys lysosomal enzymes

Question 54

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

Answer 54

IgA proteases destory IgA antibodies in mucus at mucosal surfaces

Question 55

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

Answer 55

- damage caused by enzymes or toxins - cytopathic effects - use of host as food source

Question 56

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

Answer 56

- inflammation: swelling, phagocytic enzymes, complement, scarring - antibodies and cytotoxic cells

Question 57

how can enzymes released by a pathogen cause damage?

Answer 57

tissue damage

Question 58

how can toxins released by a pathogen cause damage?

Answer 58

- fever - cardiovascular and nervous system disturbances - shock - diarrhoea - death

Question 59

how can cytopathic effects of pathogens induce damage?

Answer 59

microbes activity causes damage and kills host cells

Question 60

what are portals of exit for pathogens?

Answer 60

when pathogen leaves the body to spread to a new host

Question 61

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

Answer 61

respiratory and digestive tract pathogen

Question 62

what is chronic infection?

Answer 62

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

Question 63

what is a latent infection?

Answer 63

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

Question 64

is an acute infection short or long term?

Answer 64

short

Question 65

when is an acute infection transmissible?

Answer 65

during incubation, prodromal, disease or recovery period

Question 66

when can latent infections be transmitted?

Answer 66

cannot when not multiplying

Question 67

when can chronic infections be transmitted?

Answer 67

always