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Flashcards in Host Defence Mechanisms Deck (37):
1

what are the 4 genres of host defence mechanisms?

1. normal flora
2. mechanical processes
3. Immune system
4. physical barriers

2

name 5 physical barriers

1. tears- lysozyme
2. Skin- dry, acidic, sweat containing fatty and lactic acid.
3. filtration of inhaled air by turbinate bones.
4. commensal bacteria in GI and skin
5. acidity of stomach and vagina

3

what is the hosts mechanical defences?

Mucociliary action and Flushing

4

whats Mucociliary action?

mucous prevents attachment and is pushed to the throat by ciliated epithelia.

5

define flushing

flow of fluid over mucosal surface removing bacteria.

6

give some exiles of flushing?

1. urine flow over urogenital tract
2. gut contents in GI tract
3. tears over cornea

7

how is the normal human flora a defence mechanism?

1. exclude colonisation by competition
2. induce low level antibody and react with the pathogen
3. produce antimicrobials bacteriocin and fatty acids.

8

explain 4 ways the hosts immune system acts as a defence?

1. inhibitory compounds
2. specialised immune cells
3. secretory immunity
4. systemic immunity via Ab

9

name 5 inhibitory compounds

1. HCL - stomach
2. Bile salts and fatty acids.
3. Defensins
4. Lactoferrin and transferrin
5. Lysozyme.

10

whats the action of lysozyme?

cleaves peptidoglycan and disrupts the cell wall found in saliva and tears

11

whats the action of Lactoferrin?

found in body secretions and serum binds to free iron so inaccessible to bacteria.

12

whats the action of Defensins?

pore forming cationic peptides

13

name the specialised immune cells that are involved in the hosts defence

phagocytic cells, Kupffer cells mesagnial cells and alveolar macrophages

14

name the cells of the reticuloendothelial system

lung- alveolar macrophages
kidney- mesagnial cells
liver- Kupffer cells
peridontal tissue- gingival macrophage.

15

describe secretary immunity

1. sIgA inhibits bacterial attachment to mucosal epithelium.
2. agglutinates bacteria
3. binds inactive toxins
4. presents in colostrum so protects suckling infants.

16

define virulence

the potential for a pathogen to produce morbidity or mortality in infected hosts

17

define virulence factors

properties that enable a microorganism to establish itself on/within a host of a particular species + enhance its potential to cause disease.

18

name the 8 bacterial virulence factors

1. capsule
2. fimbriae
3. type III secretion system
4. siderophores
5. endotoxin
6. toxins
7. biofilms
8. serum resistance

19

how does the capsule protect the host?

surface polysaccharides protect against host immune defence

20

how does serum resistance protect the cell?

surface molecules mediate resistance to complement

21

how do biofilms protect bacteria?

attachment and persistence

22

how do toxins protect the cell?

secreted (exo) or membrane bound (endo) proteins cause tissue damage or inhibit tissue function.

23

how do siderophores protect bacteria?

scavenge iron and promote uptake into bacteria

24

name an endotoxin and how it works

lipopolysaccharides are components of membranes elicit immune/inflammatory response.

25

how is fimbriae a virulence factor?

adheres to host tissues and is subject to Ag variation.

26

how do type III secretion systems work?

adherence to and invasion of host tissues

27

what are the 6 stages if bacterial infection?

1. entry
2. colonisation
3. proliferation
4. invasion
5. immune evasion
6. transmission

28

how does entry occur?

1. skin is major barrier breached by bites and wounds
2. entry via mucosal surfaces

29

what is colonisation?

attachment to mucosal surfaces

30

what is proliferation?

acquisition of nutrients and overcoming Fe limitation

31

what is invasion?

entry into host tissue/cell local/systemic

32

what is immune evasion?

avoidance of the immune system via Ag/phase variation and resistance to immune effects.

33

whats the prevalence of UTI?

10-20% woman 12% men

34

what causes UTI?

90% E. coli

35

how do you treat UTI?

oral ampicillin or IV gentamicin

36

how does UTI infection occur?

contamination by bacteria from the GI tract

37

describe the virulence factors present in Neisseria meningitides

1. capsule
2. LPS
3. pilus
4 Tbp, Lbp, Hpu, HmnR, FetA
5. Opa, Opc, NhhA, NadA.