Session 6 - Pharyngitis, endocarditis

Question 1

What is the EPS matrix?

Answer 1

extracellular polymeric substances secreted by bacteria within a biofilm. The matrix promotes bacterial survival through acting as a barrier to antimicrobials

Question 2

Medical devices commonly colonised by bacteria?

What infections can arise from each?

Answer 2

• Urinary catheters > UTI
• Mechanical ventilators > pneumonia
• Prosthetic heart valves > endocarditis
• Central venous catheter > bloodstream infection

Question 3

What is bicuspid aortic valve?

Answer 3

Most common congenital heart defect. The aortic valve should have 3 cusps, but abnormal fusion of adjacents cusps during valvulogenesis leads to a bicuspid valve.

Question 4

Position of the aortic valve in the chest

Answer 4

Upper right sternal border at the 2nd intercostal space

Question 5

A systolic murmur which is heard most loudly in the upper right side of the chest is likely to be what?

Answer 5

Aortic stenosis

Question 6

How can poor dental hygiene cause endocarditis?

Answer 6

Mouth microbiota can enter the blood stream through broken gums

Question 7

Name some microbiota species found in the mouth

Answer 7

• Viridans Streptococcus (alpha haemolytic)
  S. mutans and ; S. sanguinis
• Neisseria
• Haemophilus
• Staphylococcus

Question 8

How do you classify streptococcus pyogenes?

How do you classify viridans streptococci?
Where are they found?

Answer 8

Lancefield group A , beta haemolytic streptococcus

They are alpha haemolytic (green agar plate).
Mouth commensals

Question 9

How do you classify beta-haemolytic streptococcus?

Answer 9

Lancefield classification based on cell wall antigens

Question 10

How does Streptococcus Pyogenes prevent phagocytosis?

Answer 10

• M protein
  prevents opsonisation by C3b
• Hyaluronic acid capsule
  antiphagocytic; poor immunogen bc similar to hyaluronic acid in connective tissue
• Exotoxins
  cleave IgG bound to the coccus
• Streptolysins O and S
  lyse neutrophils
  (plus RBC’s and platelets)

Question 11

• lipoteichoic acid
• fibronectin binding proteins
  are examples of what?
  Why does Strep. Pyogenes express them?

Answer 11

They are adhesins

Help the pathogen adhere to the cell, necessary for invasion

Question 12

Streptokinase is expressed by Strep. Pyogenes. What does it do?

Answer 12

Converts plasminogen to plasmin to dissolve clots

Question 13

Streptococcal pharyngitis is caused by what?

Answer 13

Streptococcus Pyogenes

Question 14

What are the monocyte cytokines?

Answer 14

IL-1
Il-6
TNF-alpha