Pathogenicity

Question 1

name the steps of the basic life cycle of a pathogen?

Answer 1

1. enter
2. attach
3. colonise
4. evade host immunity
5. produce harmful proteins
6. disseminate
7. release from host

Question 2

describe the term pathogen.

Answer 2

organism capable of causing disease

Question 3

describe the term commensal.

Answer 3

organism that is part of the normal flora

Question 4

describe the term pathogenicity.

Answer 4

ability to cause disease

Question 5

describe the term virulence.

Answer 5

ability to cause severe disease
eg. more virulent the more dangerous

Question 6

what are microorganisms?

Answer 6

agents of infectious diseases

Question 7

name 5 divisions of microorganisms?

Answer 7

bacteria
fungi
viruses
prions
parasites

Question 8

what is colonisation?

Answer 8

when microbes find a new host and start to multiply

Question 9

what leads to normal flora?

Answer 9

balance between colonised microbes and humans

Question 10

what is a microbe that causes disease called?

Answer 10

infection

Question 11

what is an endogenous infections?

Answer 11

when the source of microbe is a patients own flora

Question 12

what is an exogenous infection?

Answer 12

when the source of microbe is flora from outside a patients body

Question 13

give characteristics of koch’s postulates?

Answer 13

• microbe must be present in every case of disease
• microbe must be isolated from diseased host and grown in pure culture
• disease must be reproduced when a pure culture is introduced into a susceptible host
• microbe must be recovered from and experimentally infected host

Question 14

what is koch’s postulates?

Answer 14

germ theory of disease

Question 15

what does koch’s postulates prove?

Question 16

how do microorganisms get into the body person to person?

Answer 16

• contaminated blood or bodily fluids
• touch
• saliva
• air

Question 17

give 5 examples of how microorganisms get into a person?

Answer 17

• person to person
• fomites (surfaces)
• insects
• water
• food

Question 18

what is attachment of a microorganisms specific to?

Answer 18

host and tissue

Question 19

what allows e coli to attach to the bladder epithelium?

Answer 19

pili (fimbriae)

Question 20

describe characteristics of pili (fimbriae) in e-coli?

Answer 20

• proteinaceous
• usually in gram negative
• 4-10 nm wide
• 0.5-4 um long

Question 21

how are pili (fimbriae) in e-coli stuck to a surface?

Answer 21

covalently

Question 22

how do UTI’s colonise?

Answer 22

faeces or perineal regions

Question 23

who is most commonly after by UTI’s?
and what % of women develop a UTI at some point in their life?

Answer 23

females under 10 and between 20-40

50% of woman

Question 24

what is the main defence against UTI’s?

Answer 24

flushing action of urine

Question 25

which protein present in urine helps bind specific Escherichia coli strains in UTI's (helpful)?

Answer 25

Tamm-Horsfall protein

Question 26

which fruit helps protect against UTI's?

Answer 26

cranberries

Question 27

give 4 examples of encapsulated infections?

Answer 27

meningitis pneumonia otitis media sinusitis

Question 28

what is 4 things that commonly cause encapsulated infections?

Answer 28

streptococcus pneumoniae haemophilus influenza neisseria meningitis group B streptococcus

Question 29

what is on the outer layer of a gram positive cell and what does it do?

Answer 29

capsule layer protection

Question 30

what is the capsular function?

Answer 30

- helps mediate adhesion (colonise) - helps immune evasion - protects from desiccation (doesn't dry out) - receives carbs - encapsulated bacteria gives rise to smooth colonies - capsule material gives rise to capsular antigens

Question 31

name the 2 types of toxins?

Answer 31

exotoxins endotoxins

Question 32

what are exotoxins?

Answer 32

produced inside gram positive bacteria as part of growth and metabolism. secreted or released following lysis into surround medium.

Question 33

what are endotoxins?

Answer 33

part of outer portion of cell wall of gram negative bacteria. liberated when the bacteria die and the cell wall breaks apart.

Question 34

what are LPS molecules detected by in gram negative?

Answer 34

macrophages

Question 35

what is LPS in a gram negative cell wall?

Answer 35

lipopolysaccharides

Question 36

is LPS endotoxin or exotoxin?

Answer 36

endotoxin

Question 37

when are LPS released from a gram negative cel wall?

Answer 37

the cell lises and they are released

Question 38

what is a common syndrome that LPS (endotoxin) can cause?

Answer 38

toxic shock

Question 39

what are exotoxins?

Answer 39

proteins

Question 40

are exotoxins and endotoxins, specific or non-specific?

Answer 40

endotoxins - non specific exotoxins - specific

Question 41

what is the difference between exotoxins and endotoxins in terms of potency and relationship to cell?

Answer 41

endotoxins = low potency, part of outer membrane of cell exotoxins = high potency, extracellular/ diffusible (made inside and diffused out)