CNS Infections and Microbiology Flashcards
what are the classifications of CNS infections
- acute pyogenic (bacterial) meningitis
- aseptic (viral) meningitis
- focal infection (e.g. brain abscess, subdural and extradural empyema)
- chronic bacterial infection (TB)
what is acute encephalitis an infection of
brain parenchyma
what should your Ddx be in a patient with fever and altered mental status
Encephalitis Meningitis Meningoencephalitis Encephalomyelitis Severe sepsis syndrome due to infection elsewhere
viral meningitis is very rare - true or false
false
- it is very common, particularly in the late summer/autumn
who most commonly gets viral meningitis
children
what causes viral meningitis
enteroviruses e.g. ECHO virus, coxsackie virus
Ix for viral meningitis
Viral Stool culture
Throat Swab
CSF PCR
Tx for viral meningitis
Supportive
self-limiting
what is the expected CSF results of someone with viral meningitis
CSF WCC raised, predominantly lymphocytes
CSF protein normal or slightly raised
CSF glucose normal
what is the most common cause of viral encephalitis
Herpes simplex
but also varicella zoster, CMV, HIV, measles
what are the symptoms of encephalitis
Insidous onset; sometimes sudden Meningismus Stupor, coma Seizures, partial paralysis Confusion, psychosis Speech, memory symptoms
what is Meningismus
a set of symptoms similar to those of meningitis but not caused by meningitis
e.g. neck stiffness, headache, photophobia
in children older than 3 months and in adults, what form of HSV causes encephalitis and where does it affect
HSV-1
localised to the temporal and frontal lobes
in neonates, what HSV causes encephalitis and where does it affect
HSV-2
(acquired at time of delivery)
generalised brain involvement
what virus should be considered in the immunodeficient
CMV
what must be considered in patients when identifying the bacterial cause of meningitis
age and risk factors
what bacteria commonly cause bacterial meningitis in neonates
listeria
group B streptococci
E. coli
what bacteria commonly cause bacterial meningitis in children
H. influenza
what bacteria commonly cause bacterial meningitis in 10 to 21 y/o
meningococcal
what bacteria commonly cause bacterial meningitis in > 21y/o and elderly
pneumococcal
what bacteria is suspect in immunocompromised patients
listeria
S.pneumoniae
N.meningitidis
what bacteria is suspect in patients who have had neurosurgery or opened head trauma
staph aureus
staph epidermidis
if the patient has a fracture of the cribriform plate, what bacteria is suspected
pneumococcal
H. influenzae
what is the 3 ways that bacteria can enter the brain
1 - nasopharyngeal colonisation (of pneumococcus commonly)
2 - direct extension of bacteria (e.g. brain abscess, skull fracture)
3 - from remote foci of infection (e.g. pneumonia, UTI, endocarditis)
what does Neisseria Meningitis cause in immunocompromised patients
meningococcal meningitis
what causes the symptoms in meningococcal meningitis and what would you expect to find in the CSF
endotoxin
leukocytes
what is the appearance of listeria and who is commonly affected by it
gram positive bacilli
neonatal and elderly
immunocompromised
what is suggestive of Tuberculous meningitis
- elderly patient with Hx of TB
- non specific ill health
- poor yield from CSF
Tx for Tuberculous meningitis
Isoniazid + rifampicin
add pyrazinamide + ethambutol
triad of bacterial meningitis
fever
stiff neck
altered consciousness
who are signs of bacterial meningitis often absent or atypical in
The very young
The very old
The immunocompromised
when should a LP never be done
if confirmed or suspected raised ICP
what is important to note in a LP result in bacterial meningitis
false negative around 10-15%. Pre-LP use of antibiotics may low the positivity of culture.
what are CSF results predictive of bacterial meningitis
WBC Count >2,000 Neutrophils > 1180 Protein > 220 mg/dl Glucose < 34 mg/dl Glu (CSF/serum) <0.23 cloudy appearance
what is aseptic meningitis
non-pyogenic bacterial meningitis
what is the features of CSF in aseptic meningitis
low number of WBC
minimally elevated protein
normal glucose
who should undergo a CT BEFORE a lumbar puncture
Immunocompromised Hx of CNS disease New Onset seizure Papilloedema Abnormal level of consciousness Focal neurologic deficit
what are signs of a focal neurological deficit
non reactive pupils, abnormal visual fields, arm or leg drift
what are warning signs in bacterial meningitis
Marked depressive conscious level (GCS <12) or a fluctuating conscious level (fall in GCS >2) Focal neurology Seizure before or at presentation shock Bradycardia and hypertension Papilloedema
what is the empirical antibiotic therapy in bacterial meningitis
IV Ceftriaxone 2g bd
If penicillin allergic:
IV Chloramephenicol 25mg/kg 6-hourly with Vancomycin IV 500mg 6-hourly
what is added is listeria is suspected in bacterial meningitis treatment
IV Ampicillin/Amoxicillin
If penicillin allergic:
IV Co-trimoxazole (alone)
what should be Given to all patients suspected of bacterial meningitis before or with first dose of antibiotics
IV Dexamethasone
what bacterias which cause bacterial meningitis have vaccines
Neisseria meningitidis
Haemophilus influenzae
Streptococcus pneumoniae
how is Group B strep meningitis is neonates treated
benzylpenicillin and gentamicin
what can be given as prophylaxis to family members with patients with meningococcal meningitis
Rifampicin/Ciprofloxacin
