Lecture 2 - Microbial pathogenesis

Question 1

what are indigenous microflora?

Answer 1

all microbes (bacteria, fungi, protozoa) that reside on or within a person

Question 2

does a fetus have indigenous microflora?

Answer 2

no, colonisation happens during and after birth

Question 3

What are the main sites of indigenous microflora in humans? give some examples

Answer 3

• bacteria on skin
• oral streptococci
• gut flora
• vaginal flora

Question 4

describe our indigenous microflora on our skin

Answer 4

around 1 trillion bacteria, streptococcus and staphylococcus metabolise sweat to produce body odor

Question 5

describe oral streptococci

Answer 5

biofilms of bacteria which is ~400 cells thick of surface teeth
- dental plaque

Question 6

describe gut flora

Answer 6

more than 500 species of bacteria in the gut, weighing 3.3 pounds.
they breakdown carbohydrates, make essential nutrients like vitamins K and B12 and crowd out harmful bacteria

Question 7

describe vaginal flora

Answer 7

beneficial bacteria of the lactobacillus family. they secrete lactic acid to protect against invaders such as pathogenic yeast
- candida albicans (vaginal thrush)

Question 8

What is HPV?

Question 9

Fossil viruses

Question 10

what is symbiosis?

Answer 10

organisms living together in close association

Question 11

what is mutualism?

Answer 11

symbiosis that is beneficial to both symbionts

Question 12

what is neutralism?

Answer 12

neither symbiont is effected by the relationship

Question 13

what is commenalism?

Answer 13

beneficial to only one symbiont, but doesn’t effect the other

Question 14

what is parasitism?

Answer 14

beneficial to one symbiont (parasite) and harmful to the other (host)

Question 15

what is synergism?

Answer 15

two or more microorganisms team up to cause disease
- synergistic or polymicrobial infection

Question 16

what is a pathogen?

Answer 16

microorganism that causes disease

Question 17

what is an opportunistic pathogen?

Answer 17

has the potential to cause disease

Question 18

sites of microbial infection and shedding

Question 19

what are the bacterial portals of entry?

Answer 19

• ingestion
• inhalation
• trauma
• needlestick
• athropod bite
• sexual transmission

Question 20

Describe Kochs postulates

Answer 20

• microorganism must be found in similarly diseased animals but not in healthy ones (same symptoms)
• microorganism must be isolated from a diseased animal and grown in pure culture
• the isolated microorganism must cause the original disease when injected in a susceptible host
• the microorganism must be re-isolated from the experimentally infected animals - get same bacteria

Question 21

what is the germ theory?

Answer 21

theory states that microorganisms are the cause of many diseases.

Question 22

what was koch’s postulates originally designed to do?

Answer 22

establish a causal relationship between a causative microbe and a disease

Question 23

Koch’s original postulates were based on?

Answer 23

TB and cholera

Question 24

what are the three flaws in postulates 1, 2, and 3?

Answer 24

1: some organisms can be carried asymptomatically
2: some organisms cannot be grown in culture, and we must use PCR
3: must is replaced by ‘should’, as as infection by certain organism does not always cause disease.

Question 25

what are the periods in the course of an infectious disease?

Answer 25

1: incubation period 2: prodromal period 3: illness 4: convalescent period

Question 26

what is the incubation period?

Answer 26

time between infection and onset of symptoms

Question 27

what is the prodromal period?

Answer 27

patient feels 'out of sorts' but no disease symptoms

Question 28

what is the illness period?

Answer 28

experience of symptoms associated with disease

Question 29

what is the convalescent period?

Answer 29

time during which patient recovers

Question 30

what are the steps in pathogenesis of infectious diseases?

Answer 30

1: entry 2: attachment 3: multiplication 4: invasion or spread (aka systemic disease) 5: evasion of host defenses 6: damage to host tissues

Question 31

which step of pathogenesis does coughing attempt to counteract?

Answer 31

attachment

Question 32

what are the four types of human carriers?

Answer 32

passive carrier (never had disease) incubatory carrier (during incubation period) convalescent carrier (recovering) active carrier (recovered but still carries)

Question 33

what is a localised infection?

Answer 33

pathogens are contained at site of infection

Question 34

what is a systemic infection?

Answer 34

pathogen spreads throughout the body (dangerous is enters bloodstream)

Question 35

what is an acute infection?

Answer 35

rapid onset and rapid recovery

Question 36

what is a chronic infection?

Answer 36

slow onset and slow recovery

Question 37

what is a latent infection?

Answer 37

recurring infection from when a pathogen was not completely eradicated after initial recovery.

Question 38

what is a secondary infection?

Answer 38

a disease that follows a primary infection (pneumonia after mild respiratory infection)

Question 39

what is microbial intoxication?

Answer 39

when the toxin the microorganism produces in vitro causes illness, and not the microorganism itself. (e.g. strep produces toxins but wont cause infection when ingested, as its site of attachment is in the respiratory system, and they cannot pass the stomach)

Question 40

what is the incubation time of a microbial toxin?

Answer 40

there is no incubation time, as it isn't an infection.

Question 41

what are virulence factors?

Answer 41

they are a measure of pathogenicity.

Question 42

the majority of pathogens are o_____________

Answer 42

opportunistic

Question 43

what is an adhesin?

Answer 43

promotes attachment onto the host cell. often paired with pili for distance - also biofilm can act as an adhesin

Question 44

what are the common virulence factors?

Answer 44

- adhesins - invasins - cytolysins - spreading factors - immunopathogenic factors - immune evasion factors

Question 45

what is a biofilm?

Answer 45

a sticky web of polysaccharides secreted by microorganisms, typically staph

Question 46

what are cytolysins?

Answer 46

a virulence factor that causes cells to lyse by binding as oligomers to pores and causing them to open and the cell to lyse by osmosis. they may do this for: - access to nutrients (Fe in RBCs) - immune evasion (WBC) - bacterial spreading