MICROBIOLOGY - CNS infections Flashcards
what does pyogenic meningitis look like macroscopically
thick layer of suppurative exudate covering the leptomeninges over the surface of the brain
exudate in basal and convexity surface
what does pyogenic meningitis look like microscopically
neutrophils in the subarachnoid space
when should you consider listeria spp as the causative organism of pyogenic meningitis
over 60s immunocompromised diabetics alcoholics neonates
what found is listeria assoc. with
soft cheese
what organisms should you consider in pyogenic meningitis in neonates
listeria
group B strep
E. coli
what organisms should you consider in pyogenic meningitis in children
H influenza
what is the most common cause of pyogenic meningitis in 10 - 21 year olds
N. meningitidis
what should be considered as cause of pyogenic meningitis in over 21s
strep pneumoniae
n. meningitidis
what should be considered in over 65s as cause of pyogenic meningitis
strep pneumoniae
listeria
what is the triad of meningism
fever
stiff neck
head ache
what rash is seen in meningococcal meningitis
non blanching purpuric rash
what are some s/s of meningitis
fever + stiff neck + headache rash fever photophobia, change in consciousness, lethargy, confusion vomiting
what is kernigs sign
pain and resistance on passive extension of the knee with flexed hip
what is the treatment of meningitis NPA
ceftriaxone + dexamethasone
what is the treatment of meningitis PA
chloramphenicol + vancomycin + dexamethasone
when should dexamethasone be started when treating meningitis
with or just before first course of antibiotics
- if already started can be started up to 12 hours after first dose
if listeria cover required what should be added
amoxicillin
or co-trimoxazole alone if PA
if recent travel to area of high rates of penicillin resistant pneumococci then what should be added
vancomycin or rifampicin
if no organism is identified how long should treatment go on for
10 days
how long should treatment go on for identified meningococcus
5 days (up to 7) ceftriaxone stop dexamethasone
how long should treatment go on for identified pneumococcus
10 days (up to 14) ceftriaxone \+ 4 days dexamethasone
how long should treatment go on for identified penicillin resistant/cephalosporin resistant pneumococcus
14 days ceftriaxone + vancomycin
+ 4 days dexamethasone
why is vancomycin not used as a monotherapy
concerned about CSF penetration
how long should treatment go on for identified listeria sp
at least 21 days amoxicillin
+ stop dexamethasone
how long should treatment go on for identified H influenza
10 days ceftriaxone
+ stop dexamethasone
how long should treatment go on for identified other gram negative bacteria
21 days agreed antibiotic regime
+ stop dexamethasone
what 4 organisms is decreased cell mediated immunity a risk factor for
listeria
strep pneumoniae
n. meningitidis
pseudomonas aeruginosa
neurosurgery / head trauma is a risk factor for what organisms
staph epidermidis
staph aureus
gram negative bacilli
fracture of the cribriform plate is a risk factor for what organism
strep pneumonia
basilar skull fracture is a RF for what organisms
strep pneumonia
h influenza
b-haemolytic strep group A
CSF shunt if a RF for what organisms
s. epidermidis
s. aureus
pseudomonas aeruginosa (aerobic GNR)
propionbacterium acnes
what are 4 complications of bacterial meningitis
purulence clusters at base of brain
invasion
cerebral oedema
ventriculitis/hydrocephalus
exudate can form around what cranial nerves
III and VI particularly vulnerable
what prevents meningitis becoming an abscess
pia
how can abscesses cause meningitis
cause secondary ventriculitis and hence meningitis
mycobacterium tuberculosis, nocardia asteroids and cryptococcus neoformans can be seen in what patients
immunocompromised patients
how is meningitis diagnosed
blood culture and coag
throat swab (meningococcal)
blood EDTA for PCR (meningococcal)
CSF fluid (LP) if clinically feasible
you should do a LP before/after antibiotics
after
what would CSF look like in bacterial meningitis
high WBC count
high neutrophils (may be lower if partially treated)
high protein
low glucose
how many tubes of CSF should be taken
4
what are the 3 tubes of CSF for
1 - haematology - cell count, differential
2 - microbiology - gram stain, culture
3 - chemistry - glucose, protein
4 - haematology
why might CSF be culture negative
pre-LP antibiotics
where is N. meningitidis found
throats of healthy carriers
how does gain access to the meninges
through the blood stream
where may N. meningitidis be found in the CSF
in leukocytes
what causes the symptoms of N. meningitidis
endotoxin
N. meningitidis disease occurs most in
young children
10 - 21
who gets vaccinated against N. meningitidis and why
army
prevent epidemics in camps
apart from meningitis what other local disease can N. meningitidis cause
conjunctivitis
arthritis
N. meningitidis is gram ___ and what shape
gram negative diplococci
H. influenza is part of what normal microbiota
throat
H. influenza requires what for growth
blood factors
what is the most common cause of meningitis in children under 4
H. influenza type b
is there a vaccine against H. influenza
yes
H. influenza is gram ___ and what shape
negative
coccobacilli
where is strep pneumonia commonly found
nasopharynx
who is at risk of strep pneumoniae
hospitalised patients CSF skull fracture diabetics alcoholics young children
strep pneumoniae can be related to CNS devices such as
cochlear implant
some strep pneumoniae meningitis can occur secondary to what
strep pneumoniae pneumonia
is there a vaccine for strep pneumoniae
yes
strep pneumoniae is gram ___ and what shape
positive
cocci in chains
listeria monocytogenes is gram ____ and looks like what
negative
bacilli/rods
who is at risk of listeria monocytogenes
neonates
immunocompromised esp malignancy
> 55
what is the antibiotic of choice for listeria monocytogenes
amoxicillin
when can tuberculosis meningitis be seen
reactivation of latent TB in the elderly
what might you do if you suspect tuberculosis meningitis
chest XR to see if previous TB
what is the treatment for TB
isoniazide + rifampicin + pyrazinamide + ethambutol
name a type of fungal meningitis and when it might be seen
cryptococcal meningitis
HIV when CD4 < 100
crytococcal meningitis will have an ____ picture on CSF and a subtle ____ presentation
aseptic
neurological
what is the treatment for crytococcal meningitis
IV amphotericin / flucytozine
fluconazole
true/false
neutrophilic pleocytosis and low CSF glucose always means bacterial meningitis
false
what should be disrupted and swabbed or aspirated in early patient management for microscopy and culture
any petechial or purpuric rash
who should get a LP
all adults with suspected meningitis except if CI or there is confident clinical dx of meningococcal meningitis with typical meningococcal rash
what are some CI to LP
immunocompromised
papilloedema
focal neurological signs
altered consciousness
how can secondary cases of meningitis be prevented
report to public health
prophylactic treatment for close contacts
what is the prophylaxis regimen for 12+ ages
600mg rifampicin 12 hourly 4 doses
or
ciprofloxacin single dose
what warnings should be given about rifampicin
red urine
reduced efficacy of OCP
staining of contact lenses
what is the prophylaxis regimen for children under 12
125mg ceftriaxone IV single dose
or
in children aged 3-11 can do 10mg/kg 4 doses orally of rifampicin
what vaccines for meningitis exist
n. meningitidis serogroups A and C
H influenza b
strep pneumonia
steroids have the most benefit in what type of meningitis
pneumococcal
when should steroids not be given
post surgical meningitis severe immunocompromised meningococcal septic shock allergy
who should undergo CT prior to LP to rule out raised ICP
immunocompromised history of CNS disease new onset seizure within 1 week of presentation papilloedema abnormal level of consciousness focal neurological deficit
what is the most common cause of meningitis
viral
when is viral meningitis most common
late summer/autumn
what is the most common cause of viral meningitis
enteroviruses - ECHO virus
what other viruses cause viral meningitis
coxsackie
HSV
how is viral meningitis diagnosed and treated
viral stool culture
throat swab
CSF PCR
supportive tx
what is aseptic meningitis
non pyogenic / pus forming
infective or non-infective
what are some infectious causes of aseptic meningitis
syphilis, tb, crytococcus, hsv, lyme disease, others
what are some non-infectious causes of aseptic meningitis
vasculitis
sarcoidosis
drugs - cotrim, NSAIDs
what is encephalitis
inflammation of brain parenchyma
what causes encephalitis
HSV, VZV, CMV, HIV
how should encephalitis be investigated
LP, EEG and MRI
what would MRI in HIV show
bilateral focal temporal lobe enhancement
what should be started as prompt therapy in encephalitis
aciclovir
a single abscess is caused by
local extension e.g. mastoiditis or direct implantation e.g. skull fracture
multiple abscess are caused by
haematogenous spread
where do multiple abscesses tend to occur
at white grey matter border
what does an abscess look like
central necrosis
oedema
fibrous capsule
what are some s/s of abscess
fever
raised ICP - headache, drowsy, focal neurological signs
how is abscess ix and tx
CT or MRI
aspiration for culture and tx
neurosurgical referral for urgent drainage
E coli is gram ___ and what shape
negative
rods
how does bacterial meningitis cause hydrocephalus and raised ICP
inflammation of the leptomeninges and CSF within subarachnoid space - arachnoiditis which can later cause lack of CSF absorption
what causes progressive multifocal leukoencephalopathy
JC virus causing demyelination
what are some RF for JC virus
immunosuppression
AI disease
use of MS drugs e.g. tysabri
ix progressive multifocal leukoencephalopathy
LP: JC virus DNA and multifocal enhancing lesions on imaging
CSF: what kind of meningitis: cells - lymphocytes negative gram stain for bacteria negative bacterial antigen detection protein normal/slightly high glucose normal
viral
CSF: what kind of meningitis: cells - neutrophils/polymorphs gram stain and bacterial antigen positive high protein low glucose
bacterial
CSF: what kind of meningitis: cells - lymphocytes gram stain for bacteria - positive or negative bacterial antigen detection - negative protein - high or very high glucose - low
TB
