Block 2: Virulence & Risk Factors

Question 1

What are the virulence factors of Meningococcus?

Answer 1

Polysaccahride capsule

IgA protease

Lipooligosaccharide (LOS)

• –Endotoxin*
• –Responsible for the petechial rash*
• –Endotoxic shock (septic shock)*

Question 2

What 2 risk factors are related to meningococcus?

Answer 2

a complement deficiency (C5-C8)

Asplenic patients

Question 3

What is a major VF for Gonococcus?

Answer 3

•Antigenic and Phase variation

• has ability to express numerous different pili, it can change the pili at any time
• amino acid sequences of the pili vary, therefore the pili are antigenically distinct

–During an infection Gonococcus can evade detection by the hosts’ immune system by changing the pili it expresses

-can also turn on or off the production of pili (phase variation)

–***Antigenic variation occurs with pili, OMP and LOS***

•Antigenic variation accounts for

– chronicity of infection and lack of protection against subsequent gonococcal infections

Question 4

What are the two key VFs for Hib (serotype B)?

Answer 4

•Polyribitol phosphate capsule (PRP) - antiphagocytic

•IgA protease - colonization on mucous membrane

Question 5

VF’s for Pertussis?

Answer 5

• Filamentous hemagglutinin (FHA), pertactin, fimbriae (adherence)
• Tracheal cytotoxin (TCT) – ciliostasis, destruction to ciliated resp cells
• Adenylate cyclase toxin (ACT) – increase in respiratory secrtions (↑cAMP), release of insulin from pancreas
• Pertussis toxin (PTx) – increase in resp secretions (↑cAMP), inhibits monocyte migration, inhibits phagocytic killing, increase in insulin secretion (hypoglycemia), promotes lymphocytosis

Question 6

What are the most important VF’s for P. aeruginosa?

Answer 6

1. Alginate capsule

–Anti-phagocytic

–Mucoid strains cause significant respiratory tract infections in Cystic fibrosis patients

2.Exotoxin A – blocks protein synthesis at EF-2

–similar to diphtheria toxin but not as potent

3. Pyocyanin – tissue damage

–catalyzes production of H2O2 and superoxide (toxic forms of O2)

4. Phospholipase C – tissue damagee by breaking down lipids and lecithin facilitating tissue destruction and spread

5. Endotoxin (LPS) – septicemia