Microbiology of meningitis Flashcards
meningitis definition
inflammation of the meninges
can be caused by bacteria, viruses and protozoa
other causes: cancer, inflammatory diseases and drugs
encephalitis definition
inflammation of the Brian and severity is variable
causes are HSV, parasites, autoimmune diseases, certain medications
what is the CNS composed of
brain and spinal column
cerebra-spinal fluid
clear fluid
occupies subarachnoid space and ventricular system
around and inside brain and spinal cord
cushions brain
infections of the CNS
normally sterile and well protected
has poor immune function
infections generally originate from the bloodstream
severe trauma may result in CNS infection
meninges definition
system of protective membranes enveloping CNS
label the image
what is the blood brain barrier
separation of circulating blood and the CSF in the central nervous syste m
vasogenic brain oedema cause
BBB injury
with association alteration in albumin transcytosis
in many forms of CNS infections
tight junctions
zonula occludens
closely associated areas of 2 cells whose membranes join together forming virtually impermeable barrier to fluid
meningitis with antibiotics
risk of neurological disorders
meningitis without antibiotics
high mortality rate
symptoms of meningitis
fever
photophobia
nuchal rigidity
altered mental status
purpuric rash
headache
common meningitis pathogens in neonates
E coli
group B streptococci
listeria monocytogenes
common meningitis pathogens in infants/children and adults
Neisseria meningitidis
strep pneumoniae
haemophilus influenza
common meningitis pathogens in immunosuppressed patients
cryptococcus neofromans
l. monocytogenes
Nuchal rigidity
stiff neck
sign of meningeal irritation
present when the neck resists passive flexion
Kernigs sign
elicited with patient in supine position
thigh is flexed on abdomen with knee flex
elicit pain when knee extends
Brudzinskis sign
elicited with the patient in the supine position
positive when passive flexion of the neck results in spontaneous flexion of the hips and knees
Glass test
purpuric rash that doesnt fade under pressure
sign of meningococcal septicaemia
what are the common meningitis pathogens
streptococcus pneumoniae
group B streptococcus
neisseria meningitidis
haemophilus influenzae
listeria monocytogenes
escherichia coli
label the image to display Neisseria meningitidis interaction with the BBB
label the image of pathophysiology of meningitis
neisseria meningitidis
gram negative diplococcus, intracellular
what is in the image
Neisseria meningitidis
pathogenicity factors of meisseria meningitidis
type IV pilus involvedi n mucosal colonisation
polysaccharide capsule helps avoid phagocytosis
major toxin: lips-oligosaccharide endotoxin
what are the 6 serotypes of N.meningitidis
A
B
C
W
X
Y
type IV pilus in mucosal colonisation
main means of meningococcal adhesion onto host cells
pilus-mediated adhesion
induces formation of microvilli-like structures at the site of interaction
trigger bacterial internalisation
consequence of pill-induced signalling
reorganisation of actin cytoskeleton
leads to formation of membrane protrusions
engulfing bacterial pathogens into intracellular vacuoles
polysaccharide capsule helps avoid phagocytosis
major toxin
lips-oligosaccharide endotoxin
NMEC
neonatal meningitis E coli
type of extra intestinal E coli
commonly inhabits in GI tract, perinatal transfer form mother
most frequent cause of gram-negative meningitis in neonates
NMEC important factors in pathophysiology
K1 capsule
OMPA and type 1 pili for adhesion and invasion
CNF-1 and IbeA for invasion
attachment of NMEC
mediated by type 1 pili binding to CD48 and OmpA (outer-membrane protein A) binding to ECGP96
NMEC invasion
involves cytotoxic necrotizing factor 1 (CNF1) binding to 67 kDa laminin receptor (67LR; also known as RPSA) as well as type1 pili and OmpA binding their receptors.
why is NMEC protected from the host immune response
by its K1 capsule
invasion into macrophages may provide replicative niche
for high bacteraemia
allows generation of sufficient bacteria to cross BBB
categories of NMEC pathogenicity factors
adhesions
immune evasion
iron acquisition
invasion factors
toxins
NMEC adhesins
OmpA
S-fimbriae- bind sialic acid of human cell surface glycoproteins (type 1 pili)
NMEC immune evasion
K1 capsule, antiphagocytic
iron acqusition NMEC
enterobactin
NMEC innvasion factors
IbeA receptor binding
NMEC toxins
cytotoxic necrotising factor
CNF1
processing of lumbar puncture
appearance
cell count
centrifugation
gram stain
culture
further tests
CSF appearance: clear/colourless
normal
CSF appearance: turbidity
WBC’s
possibly other cells seen in microscopy
CSF appearance: red staining
RBC’s present
stroke/ haemorrhage
hallmarks of bacterial meningitis in CSF count
recruitment of leukocytes into CSF
WBC’s are polymorphonucleus, lymphocytes
bacterial meningitis has high WBC count
viral and TB meningitis has lower WBC count
in case of some WBC’s increase but bacteria isn’t visible
patient has meningitis but the bacteria killed by antibiotics
early stage meningitis
need to do antigen detection, capsule is highly antigenic e.g. latex bead assays
PCR testing for rapid diagnosis
PCR testing for rapid diagnosis
alternative to antigen testing
confirmation of gram staining
specific primers
broad-range/ universal primers
typical approach for fungi and parasites
microscopy
culture
antigen detection
PCR
treatment of bacterial meningitis
commence ASAP before microbiological diagnosis
high dose intramuscular or IV benzylpenicillin given at earliest opportunity
high does IV 3rd generation cephalosporin
antibiotic susceptibility may modify treatment
household contacts may be given prophylactic antibiotics
TB meningitis treatment
long term treatment with specialised anti-tubercular/ antifungal agents
3rd generation cephalosporins in meningitis
ceftriaxone or cefotaxime or broad spectrum activity vs gram positives and gram negatives
penetrate well into CSF
different meningitis vaccines
meningitis B
6 in 1
pneumococcal
Hib/Men C
meningitis ACWY
6 in 1 vaccine
also known as the DTaP/IPV/Hib/Hep Bvaccine, offers protection againstdiphtheria,tetanus,whooping cough,hepatitis B,polioandHaemophilus influenzae type b (Hib).
common causes viral meningitis
enteroviruses
HSV-2
HIV
LCMV
arbovirus
mumps
less common causes of viral meningitis
HSV-1
CMV
EBV
VZV
adenovirus
measles
rubella
rare causes of viral meningitis
influenza
parainfluenza
rotavirus
vaccinia
encephalomyocarditis virus
treatment of acute viral meningitis
primarily symptomatic and includes use of analgesics, antipyretics and antiemetics
oral or IV acyclovir for HSV-1 or 2 and severe EBV or VZV
