EMS lectures 11,12,13,14

Question 1

define pathogenicity

Answer 1

capability of micro-organism to cause an infection

Question 2

what are the requirements of pathogenicity

Answer 2

transmissibility
establishment in host
harmful effects
persistence

Question 3

what is the chain of infection

Answer 3

pathogenic organism –> reservoir (multiplication) –> exit source –> transmission to host –> entry into host –> host infected

Question 4

Virulence

Answer 4

degree to which microorganism can cause disease

enables relative comparison of pathogenic potential

Question 5

What are virulence factors

Answer 5

components of micro-organism that result in harmful effects

Question 6

what are virulence mechanisms?

Answer 6

Facilitation of adhesion
toxic effects
tissue damage
interference with host defence mechanism
facilitation of invasion
modulation of host cytokine reactions

Question 7

what are bacterial endotoxins

Answer 7

part of gram negative cell wall,
active component = LPS Lipopolysaccharide
- released from dead/damaged cell walked and bind to host cell receptors
induce uncontrolled cell response =

Question 8

What are bacterial exotoxins

Answer 8

protein produced in living bacteria

- produce specific host effect

Question 9

Explain Systemic inflammatory response syndrome (SIRS)

Answer 9

host response to endotoxin

• uncontrolled t lymphocytes
• uncontrolled activation of clotting cascade
• uncontrolled activation of complement

cardiac/renal failure, hypotension, tachycardia, bleeding tendency, collapse, fever

Question 10

What anaerobe causes Botulism

• how can you contract botulism
• what is the presenting complaint with botulism

Answer 10

Clostridium botulinum
- contaminated food/dirty wound

PC = diplopia, dysphagia, dysarthria, dry mouth, death

Question 11

What causes Tetanus

• what is the toxin
• what is the action
• what is the common cause of death

Answer 11

Clostridium tetani
- Tetanospasm
- inhibits neurotransmitters in CNS
Death by respiratory paraylisis

Question 12

Other diseases caused by exotoxins

Answer 12

Cholera
diptheria
whooping cough
c.dif
e.coli
scarlet fever

Question 13

What are to virulence factors of Streptococcus pyogenes

Answer 13

• promote connective tissue invasion and breakdown
• Hyaluronidase and streptokinase - break down connective tissue
  -C5a peptidase - inactivates complement component C5a
• Erythrogenic toxin - causes scarlet fever rash
  Toxic shock syndrome toxin -
  similar to syndrome of endotoxin release

Question 14

How does S pyogenes and S pneumonia inhibit phagocytosis

Answer 14

Pyogenes - M protein binds fibrinogen and masks bacterial surface

Pneumoniae - polysaccharide capsule inhibits opsonisation

Question 15

What are the components of a virus

Answer 15

genome (RNA or DNA)
capsid - protein
envelope

unable to exisit without host

Question 16

Define atherosclerosis

Answer 16

degeneration of arterial wall - characterised by fibrosis, lipid deposition and inflammation -limit blood circulation and predisposes to thrombosis

Question 17

What are the risk factors for artherosclerosis

Answer 17

age, male, family history, genetics

hyperlipidaemia, hypertension, smoking, diabetes,

Question 18

Describe atherosclerotic plaque formation

Answer 18

1) damage to intima of vessel
2) lipid accumulation in intima
3) monocyte migration and ingestion of lipids in intima
4) monocytes become foam cells
5) foam cells secrete cytokines - attrack macrophages, lymphocytes, smooth muscle cells
6) formation of atherosclerotic plaque
7) plaque grows - occludes vessel, weakens vessel wall = aneurysm, erodes vessel

Question 19

What are the differences between a clot and a thrombus

Answer 19

Clot
- stagnant blood, enzymatic process, elastic, adopt vessel wall shape

Thrombus
- w/i body during life, platelet dependant, firm

Question 20

What are platelets

- what do they secrete

Answer 20

Fragments of megakaryocytes
bind to collaged exposed by endothelial damage and become activated

secrete alpha granules - fibrinogen, fibronectin
dense granules - chemotactic chemicals

Question 21

Define Embolus

Answer 21

mass of material able to lodge in vessel and block it

can be endo/exogenous

Question 22

What is the commonest emboli

• risk factors
• effect of size

Answer 22

Pulmonary emboli

• Factor 5 leiden deficiency, Protien S deficency
• smoking, pregnancy, obesity, heart failure, immobility,

SMALL - pulmonary hypertension
medium - V/Q mismatch, cardiac/ resp failure
Large = death - saddle emboli

Question 23

What is a systemic emboli

Answer 23

arise with in heart and arterial circulation

Question 24

What is an infective emboli

Answer 24

usually from infected heart vales

- effects compounded by infective nature - lead to mycotic aneurysm formation

Question 25

What is a tumour embolism

Answer 25

parts of tumour break of when penetrating wall - route for dissemination

Question 26

What are the types of gas emboli and when do they occur?

Answer 26

Air - vessels opened to air - obstetric procedures - chest wall injury >100ml to cause clinical effects Nitrogen - decompression sickness - the bends

Question 27

Explain what an amniotic fluid embolism is - frequency - causes

Answer 27

increased uterine pressure causes amniotic fluid into maternal uterine veins = 1:50,000 - lodge in lungs --> resp distress

Question 28

what is the common cause of a fat embolism - % fatality - what does it cause

Answer 28

- trauma - 15% - sudden resp distress

Question 29

How can foreign body emoblism occur - common in who? - lead to?

Answer 29

particles injected IV - IVDU - granulomatous disease

Question 30

define hypoxia

Answer 30

state of reduced tissue oxygen availability

Question 31

Define ischaemia

Answer 31

pathological reduction in blood flow to tissue | results in tissue hypoxia

Question 32

How harmful is ischaemia

Answer 32

short duration - cell injury reversible prolonged - cell death by necrosis = irreversible cell damage

Question 33

When will therapeutic reperfusion work? | What happens if ischaemic tissue is reperfused?

Answer 33

- is ischaemia is reversible | - reactive o2 species will call further cell damage = reperfusion injury

Question 34

define infarction | - common causes

Answer 34

ischaemic necrosis caused by occlusion - thrombosis, embolism - vasospasm, atheroma expansion, volvulus, AAA, - venous occlusion

Question 35

Morphology of infarction | - how is it classified

Answer 35

Classified by colour Red infarction - hemorrhagic - dual blood supply/venous infraction White infarction -anaemic - single blood supply therefore totally cut off

Question 36

define shock

Answer 36

systemic reduction in tissue perfusion decrease in o2 delivery to tissues -imbalance o2 delivery and consumption - leads to cellular hypoxia

Question 37

what are the cellular effects of shock

Answer 37

``` membrane ion pump dysfunction intracellular swelling leakage of centents inadequate regulation of intracellular pH anerobic respiration - lactic acid ```

Question 38

What are the SYSTEMIC effects of shock

Answer 38

alterations in serum pH endothelial dysfunction - vascular leakage stimulation inflammatory and antiinflammatory systems end - organ damage

Question 39

Explain hypovolaemic shock - presentation - causes - what happens

Answer 39

Intra-vascular fluid loss lower venous return to heart, lower stroke vol, decreased cardiac output Increased stroke vol rate (vasocontriction) present - cool, clammy, shut down causes - haemorrhage, diarrhoea, vomiting, heatstroke, third spacing

Question 40

What is third spacing

Answer 40

loss of fluid into internal body cavities

Question 41

explain cardiogenic shock

Answer 41

cardiac pump failure - low Cardiac Output - increased Stroke vol rate - myopathic - muscle failure -arrythmia related - abnormal beats - mechanical - extra-cardiac - obstruction 60-90% mortality

Question 42

explain distributive shock

Answer 42

severe vasodilation - low SVR increase Cardiac Output - flushed bounding heat = septic shock, anaphylactic shock, neurogenic shock, toxic shock syndrome

Question 43

explain anaphylactic shock

Answer 43

type 1 hypersensitivity reaction | vasodilation

Question 44

neurogenic shock

Answer 44

spinal injury, loss of sympathetic vascular tone | vasodilation --> shock

Question 45

toxic shock syndrome | - cause

Answer 45

exotoxin - s.aureus, s.pyogenes nonspecific binfing of class 2 MHC to T cell receptors massive cytokine activtion - decrease SVR

Question 46

How common is inborn metabolic disease

Answer 46

RARE | 1-2000 live births

Question 47

What are the clinical effects of hyperammoneaemia toxicity | - what is the cause

Answer 47

ammonia accumultion dyr to urea cycle defect -lethargy, poor feeding, vom, thachypnoea, convulsions, coma, death

Question 48

what accumulates in porphyrais - signs acute porphyria - signs photosenstive porphyria

Answer 48

Porphyrins Acute = Abdo pain, vom, insomnia, palpatatoin, HBP, anxiety, seizure,breathing probs, red/brown urine, muscle pain Photosensitve porphyria - sensitivity to sun, painful erythema, blisters, itching, fragile skin, inc hair growth, red/brown urine

Question 49

when can inborn errors of metaboilism be diagnosed

Answer 49

Presymptomatic population screening Investigation of symptomatic individuals

Question 50

Test for inborn errors of metabolism

Answer 50

urine metabolic screening

Question 51

What prenatal screening is available - neural tube defect - down syndrome

Answer 51

Neural tube defect - 16 week ultrasound, maternal serum and Amnoitic fluid AFP Down syndrome - 1st trimester - PAPA, HCG, nuchal translucency - 2nd trimester - maternal serum AFP, HCG, inhibin and estrol