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Micro - Neisseria Species (ii) - N Meningitides (the meningococcus)…
Micro - Neisseria Species (ii) - N Meningitides (the meningococcus)
Intro
common cause of community-acquired meningitis + meningococcal sepsis BSI
outbreaks + epidemics associated with pilgrimages to Mecca + Medina
transient asymptomatic carriage
in nasopharynx of 5-10% of people
rate highest in 15-20 y/os (25%)
uncommon in v young
some strains a pathogenic
cause invasive meningococcal disease (IMD)
incubation = 1-10 days
droplet spread (aerosolisation of resp secretions)
Risk factors
environment
overcrowding
close contact with case/carrier
endemic area
seasonal effect (e.g. strain A during dry season in African meningitis belt)
patient
splenectomy / hyposplenism / asplenism
HIV
complement deficiency
properdin (+ve regulator of complement activation) deficiency
young age
acute viral resp infection
extreme fatigue
Serotypes
13 based on capsule polysacc type
most invasive are...
A
in African meningitis belt
in Mecca
highly immunogenic capsule - antiphagocytic - hides immunogenic outer membrane proteins (aka blebs)
B
in Ire (vaccine now)
capsule is poor immunogenic (was hard to make vaccine for)
C
in Ire (vaccine now)
highly immunogenic capsule - antiphagocytic - hides blebs
outbreak in Nigeria in 2013-14
W135
in Mecca
Y
have pili + fimbriae for attachment
when organism dies endotoxin (LOS released)
Symptoms
headache
fever
neck stiffness
photophobia
vomiting
non-blanching rash
may merge + cause skin loss
septicaemia - sepsis
DIC
multiorgan failure
WATERHOUSE FRIDERICHSEN SYNDROME (bilat adrenal haemorrhage mainly seen in N Meningitides)
less commonly
pericarditis
pneumonia (esp serotype Y)
conjunctivitis
septic arthritis
endophthalmitis
effects of endotoxin
increased vasc permeability
pathological vasoconstriction (gangrene risk) + vasodilation
loss of thromboresistance, activation of coag -> DIC
blood vessel wall damage
shock
skin lesions
thrombosis
myocardial dysfunction
post recovery complications
learning disability
skin/digit loss
epilepsy
long term neurological problems
mortality
100% if untreated
10-15% even with Tx
pia + arachnoid inflamed, pus accumulates @ base of brain
Lab investigations
blood for culture + PCR
CSF
3 bottles
RCC
WCC
gram stain
skin scrapings if rash
susceptibility testing
NB send to reference lab to notify public health
Prevention
3 levels
Pop
@ risk groups
vaccine to cover all serotypes (MenB + MenACWY)
longterm antibiotic prophylaxis
case contacts
vaccine with relevant serotype
once-off antibiotic prophylaxis
vaccines
MenAfricVac (A)
MenB
MenACWY (quadrivalent conjugate)
for Africa, Saudi Arabia, Muslim pilgrimages
droplet precautions: wear mask within 1 m of patient
patient should be isolated for 1st 24 hrs on antibiotics (or else > 1m from other patients)
Tx
don't delay (if gp/paramedic, give IM injection before referral)
3GC (ceftriaxone/cefotaxime)
fluid replacement, correct coag abnormalities, if sepsis go to ICU (for ventilation/dialysis)