Neisseria: meningococci Flashcards
Can N.meningitidis be a commensal bacteria?
Yes - asymptomatic coloniser of URT
What is meningococcal sepsis?
N.meningitidis can invade blood stream -> disseminated disease = septic shock
Lab diagnostics
- CSF and blood samples (polysaccharides)
- Microscopy (Gram neg, diplococci)
- PCR
- Culture (takes too long but helpful for identifying strain)
Key virulence factor
Capsule
- Can have one or not
- Six serogroups (A, B, CW-135, X, Y, Z)
- Capsule switching is possible
- Serogroup B is not antigenic (molecular mimicry)
What cell type does N.meningitidis invade?
Mucus-producing epithelial cells -> form microcolonies
Possible complication of the formation of microcolonies?
Can fill micro-vessels -> blockage = damage
The role of carriage with N.meningitidis
- Offers some immunity
- Allows for genetic diversity/horizontal gene transfer
- Recumbency = greater antigenic variance
Surviving in the nasopharyngeal space
- Capture nutrients
- Capsule (LOS) endotoxin
- MtrCDE efflux pump
- Toxins: MafB, CdiA
Adhesion is key for pathogenicity
- Pilli
- Opa, Opc OM adhesins
Key targets for the immune system
Meningococci survival in serum
- Uptake nutrients and iron
- Capsule (anti-phagocytic)
- Resist oxidative killing with catalase, superoxidase dismutase
- Avoid complement (capsule, antigenic variation)
Antigenic variation from Pilin
- Gene conversion
- Modulate surface antigen quickly
- Variable region
- Harder to develop vaccines
Recombinogenic
- Free exchange between genes
- Gene conversion
Treatment for Meningococcal disease
- Antibiotics (AMR is rare)
- Maintenance therapy
- Vasoactive treatment
- Steroids
Meningococcal vaccine
- Multicomponent
- Quadvirulent (A,C,Y, W-135)
- Conjugate C (UK)
- Controversial B exists (molecular mimicry) Reverse vaccinology
What is reverse vaccinology?
Use the proteins/genome on the surface of microbe to generate vaccine
