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Flashcards in Professional Pathogens Deck (10)
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1
Q

What are the 5 mechanisms of virulence for Staph Aureus? (5)

A
  1. Surface proteins in cell wall - adhesins (tissue adherence, colonisation and deep infection)
  2. Secreted Proteins based on phase
  3. Capsule
  4. Coagulase Enzyme
  5. Quarum-Sensing Accessory Gene regulator to control gene expression.
2
Q

What are the cell wall adhesins in Staph Aureus? (4)

A
  1. Fibronectin binding protein
  2. Collagen binding protein
  3. Elastin Binding protein
  4. Protein A - this has immunoglobins wrong way around to help immune evasion.
3
Q

What are the main secreted proteins (exotoxins) in S. Aureus? (3)

A
  1. Cytotoxins - Form pores to lyse host cell
  2. Exfoliative toxins - proteases which target epidermal structural proteins
  3. Enterotoxins (superantigens) - stimulate massive T cell activation
4
Q

What is the role of Coagulase in S. Aureus? (2)

A

Stimulates clotting and helps immune evasion.

Used as test to distinguish S. Aureus from other staphylococci

5
Q

What is role of the thin polysaccharide capsule in S. Aureus? (2)

A

Masks cell surface features from immune system to avoid phagocytosis by neutrophils.

6
Q

What are examples of S. Aureus Infections? (3)

A
  1. Skin infections: Impetigo; Staphylococcal abscess; Furunculosis
  2. Sepsis: In patients with with vascular treatment line (e.g heart valves, cancer treatment, bone and joints etc) can cause sepsis as can seep into blood.
  3. Food poisoning: If enterotoxins are ingested can cause vomiting and some diarrheoa.
7
Q

Why is innate immune system very sensitive to Lipopolysaccharide and what is response? (4)

A
  1. Lipopolysaccharide interacts with “Toll-like receptors” on Monocyte/macrophage lineage cells and the vascular endothelium.
  2. Results in Systematic activation of:
    * Inflammatory pathways
    * Coagulation and clotting pathways
    * Makes blood vessels leaky
    Clinically manifests as Sepsis
8
Q

Where in the body are adhesins in Gram-Negative Neissera Meningitidis (Meningococcal) specially adpated to? (2)

A
  1. Respiratory Epithelium

2. Meninges - Around Brain and Spinal cord

9
Q

Where in the body are adhesins in Gram-positive Streptococcus Pneumoniae specially adpated to? What can it cause? (3)

A
  1. Respiratory Mucosa. It binds to cell membrane cholesterol.

Can cause:

  1. Upper resp infections.
  2. It can cause heart valve infections and meningitis if gets into blood and travels.
10
Q

What is the mechanism of virulence for streptococcus Pneumoniae? (3)

A
  1. Pneumolysin - Uses Forms pores and lyses ciliated and phagocytic cells.
  2. Secretes Protease which breaks down secreted immunoglobin A, preventing mucosal clearance.
  3. Other General Bacterial virulence mechanisms (like S. Aureus)