Medwiki

L06 I&I Meningitis

Meningitis

Content:

Summary/things to note:

Clinical presentation varies wide variety of microbes prompt antimicrobial therapy saves l ives

Summary

• Acute bacterial meningitis is a medical emergency – High mortality & morbidity Þ CSF sensitive to inflammation – Prompt antimicrobial therapy Þ better outcomes • Clinical presentation important – Triad Þ fever, headache, neck stiffness • Not always present Þ High fever most common (acute bacterial meningitis) • Causes are age-specific – N. meningitidis important cause Þ 3 mths-50 yrs • Diagnosis Þ CSF – Gram stain Þ direct initial antimicrobial therapy – Culture/PCR – Prior antimicrobials decrease sensitivity of Gram stain/culture • Treatment – Empiric initially Þ broad-spectrum • Change once identity/sensitivities known – N. meningitidis Þ ceftriaxone (empiric and targeted) • Viruses (aseptic meningitis) – Usually mild, self-limiting (unless also encephalitis)

QUesitons

why does it have so much optimised for meningitis also why over produce LOS

Objectives:

Learn Different classifications of meningitis Aetiology of bacterial meningitis Laboratory diagnosis of meningitis Treatment of acute bacterial meningitis

Rambles:

CNS infections

life threatening infections - high morbidity and mortality

  • CNS rather vulnerable to inflammation/oedema
    • pressure on brain stem
    • herniation
    • depression of respiratory/cardiac centre

prompt diagnosis and therapy crucial

CNS infections

  • meningitis
    • infectious- > bateria viruses fungi
    • noninfectious → lymphpma haemorrhafe drug rections autoimmune trauma
  • encephalitis
    • viruses
  • meningoencephalitis
    • viruses, parasites
  • abcesses
    • bacteria fungi
      • silent infections
  • presentations may overlap
    • imaging useful (MRi/CT)

Routes of Infection

  • haematogenous spread
    • most common
    • bacteraemia viraemia fungaemia
  • direct inovulation
    • trauma
    • iatrogenic
  • contiguous spread
    • local infection from ear or mouth infection
  • PNS→ CNS
    • viruses → herpes Rabies

Meningitis

Inflammation of meninges and CSF

they are sterile so any organism presetn is significaent

  • acute
  • purulent pyogenic→bacterial
    • from the microbiome
      • Capsulated always
    • neutrophils in CSF
  • aseptic (negative for bacterial culture)
    • Viral
      • Lymphocytes in CSF
  • chronic (granulatomous)
    • Bacterial → TB, Syphilis
    • Fungal
    • Lymphocytes in CSF

Aetiology

Bacteria

  • Respiratory microbiome
    • Neisseria meningtidis, streptococcus pneumoniae, haemophilus influenzae
  • Trauma/Surgery
    • S. aureus, S.epidermis, streps, gram negatives (ecoli pseudomonas) Viruses
  • usually mild and self limiting if without encephalitis
    • enteroviruses (coxsackie virus), herpes, measles, mumps Fungi
  • cryptococcus
    • found in HIV/Immunotherapy due to immunodeficency Parasites
  • protozoa → meningoencephalitis
    • naeglaria fowleri, toxoplasma

Age related causes neonatal

  • ecolui
  • s agalactae
  • s epidermidis
  • listeris monocytofenes
  • HSV <2 mnths
  • ecloi
  • S agalactiae
  • L monoctyogenes

2 mnths to 10 yrs

  • haemophilius influenzae
  • neisseria meningitidis
  • S pneumonuae
  • viruses

adolescent neisseria viruses

adult neissers s pneumoniae

elderly S. pneumoniae • L. monocytogenes • Gram –ves

HIV/AIDS• Cryptococcus

Trauma/iatrogenic • S. aureus • S. pyogenes • S. pneumoniae • Gram –ves (Pseudomonas)

Clinical features of meningitis signs and symptoms high fever neck stiffness photophobia neurological → headache, papilloedema (rare), altered mental state, seizures Lethargy, malaise, vomiting, diarrhoea, myalgia, arthralgia Cold/pale extremities/mottled skin Sepsis/shock Þ circulatory collapse Rash

classic triad not always presetn 20-66% fever is 95%

  • fever
  • neck stiffness
  • headache

infants generalised symptoms → lethargy, irritability, poor feeding high pitched crying bulging fontanelle

  • Rash

    • N. meningitidis
      • petechiae early (spots on skin)
      • pupuric Late →severe disease (sepsis) (bruising from capillary breakdown)
      • nonblanching → glass test (tests for capillary haemorrhage)

  • Kernig’s/Brudzinskis signs

    • meningeal irritaion
    • low severity
    • <50% positive

  • Prodromal signs (nonspecific symptoms before it gets bad)

    • nonsprecific RTI might not consider meningitis
      • Nausea, vomiting, fatigue, malaise, lethargy, cough, pharyngitis, headache, myalgia

Complications

  • death
  • amputation
  • hearing loss/blindness
  • epilepsy/cerebral palsy
  • Developmental delay

risk groups

  • infants and elderly

  • immunosuppressed

  • trauma otitis media, sinusitism dental

  • iatrogenic

  • asplenia (as haematogenous spread is most likely)

  • bacteraemia

  • neisseria meningitidis

    • gram negative
      • can be identified inside the neutrophils
    • exists in the respiratory microbiome 5-15%
      • transmission by respiratory aerosols
        • carrier to nonimmune
          • become a carrier or develop disease
            • small number develop disease
        • highly tranmissibly
      • carrige hightes in infants and adolescents
        • most at risk

  • meningitis or sepsis or both

    • sepsis alone often worse outcomes compared to meningitis

microbiology

  • virulence

    • adhesins
    • pili/OpA, OpC
      • for epithelia and endothelia

  • Porins

    • PorA/PorB
      • may help moving bacteria through the respiratory membranes

  • immune evasion

    • capsule
      • 13 types ABCWY >90% infections
      • B&W most serious
      • prevents C’ activation/opsonisation
      • sialic acids
    • sIgA protease (breaks down IgA)
    • catalase (helps them survive)

  • LOS (massivly inflammatory)

    • membrane blebs→ Excess LOS → proinflammatory

Diagnosis

  • CSF Gram stain via lumber punture

    • direct inital antimicrobial therapy
    • bacteria affected by prior Ax
    • normal CSF is clear colourless or watery
    • meningitis
      • visible turbidity = cells = bacterial
      • yellow/orange/pink blood
      • green → pus

  • bacterial → neutrophils and protein up glucose down

  • viral → lymphocyte and Protein up

Bacteria

  • culture csf and samples

    • direct narrow antimicrobials

  • blood cultures

    • haematogenous spread

  • sampling affected by prior microbials

  • Bacteria and viruses

  • PCR → rapid question how does PCR work to do this

  • high sensitivity specificity

    • not affected by previous Ax

  • small volumes of CSF (neonate/children)

Treatment acute bacterial → prompt empiric Ax

  • untreated infections and delays → siginifcatn mortality and complications

  • prehospital treatment

    • IM ceftriaxone or penicilin - NZ guidelines
      • anyone with a haemorrhagic rash or more than 30 mins from a hospital

  • empiric (hospital) IV ceftriaxone

  • N meningitidis

    • IV ceftriaxone
    • rifampicin (for contacts carriers) h. Influenzae → IV cetfriaxone s. pneumoniae → IV penicillin

  • IV vancomysin + ceftriaxone (penicillin resistant) neonated → IV penicillin / cephalosporin + gentamycin

  • covers S agalctiae, E. coli (add ampicillin if suspect Listeria) Steroids

  • dexamethasone

    • decreased complications mortality (MAYBE?)
    • affect transport of antimicrobials across bbb (maybe?) Vaccines

  • S. pneumoniae Þ most common capsule type

  • H. influenzae b

  • N. meningitidis

  • Influenza

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