BB5MOP - Week 20

What is the gram stain/shape, growth requirement, oxidase result, catalase result, motility result and structure of Neisseria?

1. Gram negative diplococci

2. Fastidious growth

3. Oxidase positive

4. Catalase positive

5. Non-motile

6. LOS

7. Pilus

8. OMPs

What carbohydrates does the gonococcus metabolise?

Glucose

What carbohydrates does the meningococcus metabolise?

Glucose and maltose

What is the function of the pilus and how does it do its function?

Helps attach the pathogen to stick to cells, by having Pil C at its tip to bind to the receptor CD46.

How can the pilus avoid the immune system?

It can change its shape.

Describe the structure of the pilus.

1. Has Pil C on tip, Pil E as the main protein.

2. Constant and hypervariable region.

How does the hypervariable region of the pilus help Neisseria evade the immune system?

The region can change using genetic recombination, creating new versions of pili.

What is phase variation in relation to the Pili?

Can switch Pili on or off to make it harder for the immune system to attack it.

How can the structure of Neisseria trigger inflammation?

LOS can trigger inflammation and is released in outer membrane vesicles called microparticles.

What do OMPs have?

Porin proteins (porA, porB) and Reduction modifiable proteins (RMPs).

What is the function of Porin protein?

Inhibit phagosome maturation and block digestion so Neisseria can live longer.

What is the function of RMPs?

Shield other Neisseria antigens from being recognised.

What are Opa proteins and what is their function?

Opa proteins are opacity protein, that are important for tight binding of Neisseria to host cells.

How can Opa proteins evade the immune system?

Can be switched using phase variation.

What is important for Neisseria to be able to cause disease?

Needs to have a capsule protecting it.

What are the five capsule compositions of Neisseria that can cause problems in humans?

A, B, C, Y and W135

What does the Neisseria vaccine target?

Targets the capsule

What does commensal mean?

Lives in the body, but does not cause harm or provide any benefits.

Which species of Neisseria is commensal?

Meningococcus

Which species of Neisseria is non-commensal?

Gonococcus

Where does the Meningococcus attack?

Attacks the nasopharyngeal epithelial cells, relies on capsule for protection.

Where does the Gonococcus attack?

Attacks the genital tract epithelial cells.

How does Neisseria deactivate complement proteins?

Recruit factor H and I from complement system and use them to deactivate complement proteins.

How else can Neisseria deactivate the complement system?

Recruits C4bp to dampen the immune response and reduce C3 convertase production.

What diseases can the Meningococcus cause?

Meningitis, bacteraemia and pneumonia

How does meningococcaemia cause disease?

1. Releases LOS in bloodstream causing massive pro-inflammatory response.

2. Loss of protein and fluid because blood vessel walls are relaxed and more permeable.

What are the properties of Chlamydia?

Obligate intracellular parasites that can only live and replicate inside a host cell.

What are the two life forms of Chlamydia?

Elementary bodies (EB) and Reticular bodies (RB)

Describe the elementary body of Chlamydia.

Extracellular form, that is small and inactive and resistant to harsh conditions.

Describe the reticulate body of Chlamydia.

Larger and more active.

Describe the process of how Chlamydia infects a cell.

1. EB inside the host cell and gets converted into an RB.

2. RB replicates inside the host cell.

3. RB back into EB, new EBs burst the host cell and are released, releasing the replicated RBs.

What is the issue with the LOS of Chlamydia?

It is an endotoxin, but does not trigger much of an inflammatory response.

What is a major outer membrane protein (MOMP)?

Forms channels in the outer membrane acting as a porin, MOMP is unique for each species of Chlamydia.

Define biovars.

Biological variety of an organism.

Define serovars.

Serum variety of an organism.

What are the two biovars of trachomatis and state their invasiveness?

1. Trachoma - not invasive

2. Lymphogranuloma venereum (LGV) - invasive

How does Chlamydia avoid the immune system?

Inhibition of lysosome function and inhibition of host cell death.

How is the lysosome function inhibited by Chlamydia?

Blocks fusion of lysosome to inclusion bodies so cannot be digested.

What type of cells does Chlamydia attack?

Epithelial cells

What four serovars cause trachoma?

A, B, Ba and C

What serovars cause genital urinary tract diseases?

D-K

What five serovars cause LGV disease?

L1, L2, L2a, L2b and L3

What does an infection of Chlamydia cause?

Inflammation, releasing of cytokines recruiting more immune cells increasing chronic inflammation.

What are the treatments of Chlamydia?

Single dose of azithromycin and doxycycline