Entry Establishment And Prolif Of Infection

Question 1

Challenge dose

Answer 1

No if microorg inoc

Question 2

Infective dose

Answer 2

No of microorg needed to produce disease (related to virulence)

Question 3

Organisms assoc with host tissue surf to initiate dis by

Answer 3

Motility and chemotaxis
Adherence
Invasion
(Host D if it doesn’t succeed)

Question 4

Motility and chemotaxis aid in colonisation

Answer 4

And association between microbes and host surfaces, eg flagella, actin polym, endoflagella

Question 5

Adherence aids in host tissue assoc

Answer 5

Cell surface adhesins bind to spec host cell surf rec ECM components and other ligands (eg complement) with cellular recs

Question 6

Spec recs involved in bact adhesion

Answer 6

Incle saccharide conjugates of glycolipids/pros or peptide seq of host surf pro
Some rec expr on by certain tissue cells so pathogen may exhibit tropism - selective adherence

Question 7

MSCRAMMs

Answer 7

Made by g+ve bact
CW assoc pros anchored to CW by spec aa motif recognised and cleaved by sortase and so tethers by covalent interaction to peptidoglycan
(Eg cause pentapeptide S aureus xbridge)

Question 8

CW assoc pro fx

Answer 8

Adherence bind to matrix pros eg fibrinogen, fibronectin, elastin
Contrib to biofilm formation that promote persist in host
Invasion of epi and ando cells eg Fn bind pro of S aureus and grp A strep
Host imm D evasion
Nutrient acquisition

Question 9

Invasion of host cells

Answer 9

Key in some pathogenesis. Some bact have surf comp (invasins) to drive cellular uptake, some inject pros to induce uptake (Fn bind pros of S aureus - bind Fn, form xbridge with major integrin rec, promote signal cascade for uptake by host cell
Many G-ve are invasive

Question 10

Host D

Answer 10

Non spec host factors

Spec host resp

Question 11

Cystic fibrosis

Answer 11

Mutation in CFTR gene cause Cl ion channel malfunction
Produce thicker secretions, can block some narrow passages/ ducts can cause favourable conditions for some pathogens (eg s aureus)

Question 12

If dis doesnt req colonisation and prolif what can it use

Answer 12

Ingestion if preformed toxins (intoxications)

Eg botulism, mycotoxosis, excessive imm resp to antigens - hypersensitivity

Question 13

Preformed toxin eg aflatoxin

Answer 13

Mycotoxin prod by aspergillus fungi. A potent carcinogen directly correlated with adverse health eg liver cancer in many species

Question 14

Preformed toxin eg staph enterotoxins

Answer 14

Food poisoning, enterotox with emetic activity

Question 15

Microb nutrient acquisition problems

Answer 15

At most tissue surfaces, nutrient supply is limiting

Question 16

Microb nutrient acquisition adaptations

Answer 16

Some pathogens entirely dep on host for essential GF, etc
Entry into host cells allows enviro with existing E production machinery
Enz such as proteases and glycosidases and lipases used in nutrient accessibility

Question 17

Host sequestering of Fe

Answer 17

Haemoglobin, transferrin, lactoferrin, EC iron is bound with high affinity transferrin (when transferrin bund ability exceeded Fe also chelated by many plasma molecules (aa, albumin, citrate)

Question 18

Fe access by microorgs

Answer 18

Fe haemostasis disorders influence susceptibility

Bact pathogens have manh mechs eg binding pros like siderophores and cell envelope assoc transport mech