Microbiology VTL - Infections of the CNS

Question 1

Definition and causes of meningitis

Answer 1

• Inflammation of meninges +/- cerebrum (meningo-encephalitis)
• Causative organisms include:
  
  • Streptococcus Pneumoniae (second most common)
  • Neisseria Meningitidis (most common)
  • Haemophilus Influenxae
  • Listeria Monocytogenes (second most common in neonates)
  • Group B Streptococcus (most common in neonates)

Question 2

What other CNS infections are worth knowing about?

Answer 2

• Viral encephalitis (confusion, fever +/- seizures)
• Intra-cerebral TB (sub-acute, CN lesions usual on II/IV/VI/IX)
• HIV brain disease (encephalitis, dementia, neuro-syphilis, TB, cryptococcus, toxoplasmosis, opportunistic infection)
• PMLE (progressive motor dysfunction, immunocompromised, JC virus)
• Intracerebral toxoplasmosis (toxoplasma gondii, headache, seizures, focal CNS signs, immunocompromised, multiple enhancing lesions in basal ganglia)
• Cryptococcal meningitis (immunodeficiency, SOL or meningo-encephalitis)

Question 3

When is LP contraindicated?

Answer 3

• Brain shift
• Rapid GCS reduction
• Respiratory/cardiac compromise
• Severe sepsis
• Rapidly evolving rash
• Infection at LP site
• Coagulopathy (including INR ≥4, platelets <40, DOAC, therapeutic LMWH)

Question 4

Management of bacterial meningitis

Answer 4

• Children in primary care is suspected and non-blanching rash
  
  • Urgent benzylpenicillin IM or IV
  • Transfer to hospital
• Hospital
  
  • Blood culture and LP for CSF
  • Bloods for meningococcal PCR
  • <3 months - cefotaxime plus amoxicillin (to cover listeria)
  • >3 months -cefotaxime
  • Add gentamicin if under 6 weeks
  • Vancomycin if risk of penicillin resistance
  • Steroids to reduce the risk of hearing loss
  • Notifiable diseases so must contact public health

Question 5

Presentation of meningitis

Answer 5

• Symptoms
  
  • Neck stiffness
  • Fever
  • Vomiting
  • Headache
  • Photophobia
  • Altered conscious level
  • Seizures
  • Non-blanching rash in meningococcal septicaemia
• In neonates symptoms include:
  
  • Hypotonia
  • Poor feeding
  • Lethargy
  • Hypothermia
  • Bulging fontanelles
  • Won’t settle
• Kernig’s test
  
  • Patient lying down
  • Flex one hip and knee to 90 degrees and then straighten knee
  • Stretches meninges causing pain or resistance
• Brudzinski’s test
  
  • Patient lying flat
  • Lift head and neck off bed and flex chin to chest
  • Positive sign if they involutarily flex hips and knees

Question 6

LP differences in meningitis

Answer 6

• Bacteria in the CSF will release proteins and eat up the glucose.
• Viruses won’t use glucose but release a bit of protein.
• Immune system releases neutrophils in response to bacteria and lymphocytes in response to viruses.