Lecture 8 - Neisseria Flashcards
Where does neisseria sp. fall in phylogenetic tree
Beta proteobacteria
What 3 genus’s fall under neisseriaceae
Neisseria, eikenella, kingella
What are 4 key neisseriaceae species
N. Gonorrheae (neisseria)
N, meningitidis (neisseria)
E,corrodens (eikenella)
K.kingae (kingella)
Eikenalla and kingella are pleomorphic. What does this mean
Variability in shape, sizeand staining
Describe eikenella and kingella characteristics
Gram negative
Colonies oropharnyx / URT
Opportunistic pathogens
Can get eikenella from human bite e.g. In wards - cause deep seated bone infections
Describe neisseria sp. structure membrane
Non motile Gram negative LOS Thin PG layer OMPs
What is diplococcus
Flat side which is division plane
What is size of neisseria sp.
0.6-1um
neisseria sp. are fastidious. What do they need
AA, purines/pyramadines, Vitamins. Al require cysteine as aa
What temp do neisseria sp. grow in
35-37deg c
What us unique about oxygen/co2 requirement for neisseria sp.
AEROBIC but capnophilic - like bit of co2 approx 5%
Grow with bit of co2
Describe neisseria sp. charactersists in terms of oxidase/catalase production
Oxidase positive
Catalase positive - get rid of hydrogen peroxide prude water and oxygen. 3% H2o2 drop on and if bubbles then catalase positive
Produce acid from sugars (oxidative- use to speciate between neisseria sp. )
What sugars can meningitis and gonoccos process or not
Meningococcus - both glucose and Maltose get acid
Gono- only glucose
Describe for both neisseria sp. whether they are commensel, what epilthelial they target, whether they are invasive or not, a
And whether it is purulent.
Commensal - meningococcus (approx 10%) in nasopharynx but never carry gonococcal
Target epithelial - meningococcus attack nasopharynx and gonococous genital tract
Invasive - meningococcus very invasive, gonococcus not very invasive
Purulent - both purulent
How can neisseria sp. attach
Pili which travel through plasma membrane
Tip have adhesion molecule pil c - name of one of protein domains
Where does Pil C bind in our cells
Bind CD46 receptor on cells to attach and invade
What part of pilE is constant and which part varies
N eteminus constant 5’ end
C terminus highly variable ( from 3’ end )
What is phase variation and where does it occur
Pili - turn things on and off - can vary the antigen
What does endotoxin not have if it is LOS not LPS
Lacks O antigen
So small but deadly LOS
Only has lipid A anchored inmemrbane and core sugars
Which part is toxic is LOS
LIPID A
What can bacteria cover themselves in to look like human cells and how much does neiserria have
Sialic acid
Neiserria low sialic acid - MORE INFECTIVE, EASIER TO KILL
What does sialic acid protect bacteria from
Serum factors e,g, complement cascade which is most important defence against neisssria
What does neisseria release to act as a decoy for immune system
Release LOS in blebs during division (outer membrane blebs released as “microparticles”
If deploy complement on blebs mother cell still alive and not killed.
What do the micro particles from neisseria cause
As leave organism cause GENERALISED INFLAMMATION ALL OVER BODY - deadly as general
What Momps (major outer membrane proteins) are present on n. Meningitidis
There are I-V with decreasing molecular weight
I to III are porins
IV is RMP - reduction modifiable proteins
V is opa - when it is expressed colonies are white (opacity)
What do porins inhibit
Inhibit phagosome maturation (stop lysosomal fusion) so sit inside cell
RMP are found where
Only found within pathogenic neisseria
Marker of disease
Immunogenic - immune response against them
What do 3 opa proteins do
Mediate TIGHT binding - phase variation here. E.g. 1 and 2 on 3 off etc.
(Pili mediate some binding)
Two Hypervariable domains - massively variable. Point mutations massively variable we don’t have antibodies against then
What does HS and CEA stand for after OPA
What opa bind to
Hs - bind to heparan sulphate - sugar chains that hang off proteins. By binding to this can interact also with extracellular matrix (all cells stuck to). Can also interact with integrins - across cell membrane and touch Extracellular world and send signal in cell.
CAN STIMUAKTE CELL TO CHANGE CYTOSKELETON TO EAT MICROBE SO IT CAN BE TRANSFERRED SOMEWHRE ELSE.
OPA CEA . Same principal as heparan sulphate binds CEA adhesion molecules and stimulate own uptake
Of neiserria hasn’t got _ (major virulence factor) then it is aparhogenic
Capsule
IMPORTANT
WHAT ARE THE SEROGROUPS OF NEISSERIA AND WHAT IT IS BASED ON.
A,B,C,Y,W135 based on capsule
What modified sugars are the serogroups based on?
IMPORTANT
Serogroup A - based on N-acetylmannosamine-1-phosphate
Serogroup B,C,Y,W135 - sialic acid
What do we use to generate vaccine response
IMPORTANT
The serogroup sugars
What is one way of capsular variation occurring
Horizontal DNA transfer
What element do bacteria struggle to obtain but neiserria is very good at
Iron
Neisseria good at wrestling iron from proteins
What two proteins carry and hold iron and what does neisseria do
Transferrin and lactoferrin
Bind these proteins so iron limitation jot an issue
Also have haemoglobin binding proteins
How to neisseria attach
Via pili for initial attachment then opa for tight binding
Can sit and divide now attached
Then get extension of pseudopodia - endocytosis
Internalise cell and can see dividing diplococcus.
LOS essential to stimulate cells to change membrane and start internalisation
Why does neisseria want to be endocytosed
More chance of being disseminated around the body
Just want to survive
What does transcytosis do for neisseria
Get eaten one end and spat out other end so can get into blood vessel
Even though have to deal with immune system can cause disease
What is host defence against neisseria
Innate - mucocilariy escalator and antimicrobial effectors (defensins, lysozyme, lactoferrin
In respiratory epithelium
Adaptive - secretory IgA pumped out into respiratory epithelium.
If igA there get meningococcus make proteases to chop it up to make it less affected,
COMPLEMENT (most important as once inside)
When does mothers IgG run out for babies
6+ months
Sensitive to meningitidis
What are the antibodies formed against for meningitis
Formed from exposure to relatives e,g, n.lactamica and other bugs with similar capsules e.h. Ecoli k1 and bacillus pumilis
People carry n meningitis
What key deficiencies lead to neisseria etc infections
Complement
E.g, alternative pathway - lose factor B, D ( needed to form c3 convertase), properdin (prolong c3 convertase activity)
Classical and lectin and alternative pathway
C3 factors H and I - pyogenic infections e.g, meningitidis
Membrane attack complex MAC
C5,6,7,8,9 severe neisseria infections
What is dangerous about losing C3 factors H and I
Turn C3 convertase off
If lose this then use up all C3 available in blood so can no longer activate complement
How can neisseria EVADE complement
Neisseria porin recruit Factor H and I which inactivate C3 convertase of alternative pathway
By decorating themselves with complement protective factors can turn off complement.
Recruit c4bp (binding protein) and Factor I to PILUS. get reduced C3 convertase form lectin pathway.
What does it mean by n meningitidis being a commensal and obligate human pathogen q
Commensal found living on body
OBLIGATE - won’t cause disease elsewhere
What does itis at the end of a word mean
Inflammation
Meningitis is main cause of bacterial meningitis. Where is disease mostly found q
Under 5 yrs, teenagers, institutionalised people, people with complement deficiencies
What are risk factors
Smoking - breach epithelial barrier in some
Age
Previous flu
Close living (halls)
Highly polymorphic organism - change a lot
Seasonal side - winter and spring (dry cold months)
What condition from this may or may not lead to meningitis
Bacteraeimia
Describe the different world countries and the associated serogroup
Subsuharan Africa - serogroup A
Pilgrimages led to high dissemination of A,c,Y,W135
UK change over time
Serogroup B after WWI AND II
1985 hyoerendimic b serogroup
1995 hyperendemic c serogroup (towards teenagers with high mortality rate)
What are clinical conditions of meningitidis
Bacteriaema - septeciamea, meningococcoaeamia
- meningitis
- pneumonia
- initially fever and flu like symptoms, vomiting. (May resolve)
- some may get classic rash but not everyone (80% of individuals)
Why is bacteria life threatening even if doesn’t cause meningitis
- Bacterial division in blood
- shock and intravascular coagulation - see bottom paragraph
- release LOS - general systemic inflammation - los can activate complement ,PRR, coagulation pathways
Massive pro inflammatory response
- increased vascular permeability
- loss of protein, fluid, and electrolytes
- cardiac output falls, extravasculsf fluid accumulates (pulmonary oedema and respiratory failure - DEATH)
Describe meningitis infection and symptoms Nd mortality
Purulent infection lots of neutrohilis
Symptoms - headache, fever, seizures, stiff neck, photophobia (often non specific especially in young)
Rash in 50% of patients
Mortality - without antibiotics 100%
With 10% chance of death
How do you diangose in lab
Take CSF and gram stain (sensitive and specific) can see neutrophils and see organism inside
Usually use PCR to pick organisms up
Describe men c vaccine positives
Reduced infection in immunised people by 90%
Cases in other groups fell by 75% (herd immunity)
Capsular polysaccharide conjugated to protein, T cell dependant immunogen
What does the tetravalant vaccine cover
A,c,y,w135
Capsular polysaccharide conjugated to protein
Recommended for sub Saharan travel especially pilgrimage
To Mecca
What is new vaccine against
Vaccine for serogroup B
Targeted at all things used by organism to protect against complement e.g. Factor h binding protein, neisseria heparin binding Ag, nerissrial adhesin a , NZ vaccine strain
Until recently wasn’t vaccine for this - capsule is sialic acid (self Ag), no immune response.
Not adopted by NHS
How can we manage
Early recognition
Antibiotics - rapid
- penicillins (b lactamases a problem)
- cephalosporins
Close contact receive prophylactic antibiotics
Close kissing contact can increase risk by 1000 times.
