Damage To Host Cells And Tissues And Infection Outcome

Question 1

Direct damage from microbial activity

Answer 1

Metabolic
Cytolytic
EC enz

Question 2

Metabolic direct damage

Answer 2

Microorg multiply within cell, competes for nutrients, microb products may dam host cell act
Eg viral, rickettsial and chlamydia infection

Question 3

Cytolytic direct damage

Answer 3

Most dam caused when org lyses host CM

Contributes to most infections to some extent

Question 4

EC enz direct damage

Answer 4

Proteases, lipases, glycosidases contrib locally to tissue dam as digest host cellular and EC components
Can provide convenient growth substrates for bact
Eg hyaluronidase of strep
Involved in local tissue invasion during infection bact metabolic activity also causes dam eg tooth decay by oral strep sugar fermentation

Question 5

Immunopathology dam

Answer 5

Caused by inflam and imm resp during infection (indirect dam) due to release if inflam med from hist cells and microorg
Hypersensitivity reactions
Imm med danger can occur via autoAb dev

Question 6

Toxins cause dam

Answer 6

Exotoxins
Endotoxins
Superantigens
Aggressins
Modulins

Question 7

Exotoxin types

Answer 7

Mem damaging

Cellular modifying

Question 8

Mem damaging exotox

Answer 8

Enzymatic or pore forming activities may cause haemolysis cytolysis leukolysis or other effects

Question 9

Cellular modifying exotoxins

Mostly AB toxins

Answer 9

A subunit is active (toxic comp)
B subunit is binding (attachment and entry comp)
Differ in target pro/cells, action modes and effects.
Generally Toxin is internalised, A express activity within cytoplasm

Question 10

E.coli LT exotoxin

Answer 10

Pore forming

Activate adenylate cyclase so incr cAMP and release of ions into gut - diarrhoea

Question 11

C diptheria toxin (exotox)

Answer 11

A subunit act aa transfer, prev pro synth by ribosome and cause cell death

Question 12

E.coli shiga-like tox (exotox)

Answer 12

Prod by EHEC
Bund cellular glycolipids and is internalised
A cleaves glycosidic bind of a euk rib subunit so prev pro synth
Cytotoxic for many cells, neurotoxic, alter vasc perm, induce enterocyte fluid loss

Question 13

Neurotoxic clostridium (botulinum and tetani) spp toxins

Answer 13

Spec interact with neurons
Single pro activated by proteolysis
Bind via glycosides, internalised, toxins inact nurotransmitter release mech

Question 14

Endotoxins

Answer 14

Integral microorg component
Key one: Lipid A of LPS, when released by lysis interact with many factors (CD14, TLR4) cause inflam med release
Can prod fever, shock, hypotension, hyperglycaemia, dissen intravasc coag
Can be fatal

Question 15

Superantigens

Answer 15

Spec class of toxins
Non-spec act lymphocytes
Eg strep pyogenic ecotox
Staph (TSS tox)
Bind MHC class2 and induce excessive lymphokine prod

Question 16

Modulins

Answer 16

Intrinsic and EC factors that activate and modulate responses

Question 17

Fungal exotoxins

Answer 17

Prod by some fungi as 2o metabolites

Upon ingestion toxins are absorbed and can cause hepatotoxicity, mucosal haemorrhage, imm suppression, carcinogenesis

Question 18

Usual outcome to non pathogenic challenge

Answer 18

Inact of infecting organism unless there is impairment or naivety in host D

Question 19

Outcome of infect dep on

Answer 19

Microbial (virulence, dose, phenotype,etc) factors

Host (imm competence, genetics, prior exposure, stress) factors

Question 20

Possible outcomes of infection

Answer 20

Acute
Chronic
Latency
Asymptomatic carrier

Question 21

Acute outcome

Answer 21

Pathogen excretion followed by revovery or death, may be elim before spec imm resp generated

Question 22

Chronic outcome

Answer 22

Pathogen excretion followed by recovery or death

Question 23

Asympt carrier outcome

Answer 23

Show nonclinical signs but microorg persist for period after clinical recovery
Infection may be confined within tissues but can be triggered by predisposing factors
Can excrete pathogen

Question 24

Latency

Answer 24

Exhibited by some pathogens eg viruses
Can enter a non-repl phase in host, no symptoms
Can reactivate under certain circumstances

Question 25

Bacterial factors affecting outcome

Answer 25

Virulence factors
Global regulators of virulence, mutations in regulatory loci
Antibio res

Question 26

Hist factors affecting infection outcome

Answer 26

Genetic susceptibility
Existing factors
Diet, gen health, other dis
Stress
Age

Question 27

Enviro factors affecting outcome of infection

Answer 27

Weather
Climate
Crowding
Hygiene
Conditions (localised infection could become systemic under certain condition

Question 28

End Outcome of infection

Answer 28

Complete recovery
Recover with persistent dam
Persistence and carrier
Death