Infectious Disease

Question 1

Clinical presentation of bacterial meningitis

Answer 1

• Headache, stiff neck (nuchal rigidity),
• Fever
• Depressed consciousness
• Hydrocephalus from obstruction
• Inflammatory response into parenchyma → seizures
• Hyperemia → infarction of cranial nerve palsies

Question 2

Diagnosis of bacterial meningitis

Answer 2

• Need an LP to diagnose
  
  • evaluate CSF profile
• • blood cultures + neuroimaging
• Some patients need CT/MRI before LP:
  
  • focal neuro deficits
  • decreased level of consciousness
  • papilloedema
  • suspected focal CNS infection (empyema, abscess)
  • immunocompromised

Question 3

Common organisms for bacterial meningitis < 2 mo.

Answer 3

• Streptococcus agalactiae (Group B) = 86%
• Gram Negative Rods = < 5%
• Listeria Monocytogenes = < 5%
• Streptococcus Pneumoniae (Pneumococcus) = 2-5%

Question 4

Common organisms for bacterial meningitis 2-24 mo.

Answer 4

• Strep pneumo = 50%
• Neisseria Meningitides = 10-15%
• Strep Agalactiae (Group B) = 10-15%
• Hemophilus influenzae = 5-10%

Question 5

Common organisms for bacterial meningitis 2-34 yrs.

Answer 5

• Neisseria meningitis = 40%
• Strep pneumo = 40%
• Hemophilus influenzae = 5-10%
• Strep agalactiae (Group B strep) = <5%

Question 6

Common organisms for bacterial meningitis >34 yrs.

Answer 6

• Strep pneumo = 50-70%
• Neisseria menigitidis = 10-25%
• Hemophilus influenzae = 1-10%
• Listeria monocytogenes = 5-10%
  
  • >25% @ > 60 yrs. or immunocompromised

Question 7

CSF profile in bacterial meningitis

Answer 7

• WBC = 100-10,000
• cell type = PMNs
• Glucose = low
• Protein = elevated
• cultures = + for bacteria
  
  • gram stain

Question 8

CSF profile in viral meningitis

Answer 8

• WBCs = 10 - 2,000
• Cell type = mononuclear (lymphocyte)
• Glucose = normal
• protein = normal/slightly elevated
• cultures
  
  • +/- for viral
  • • for bacteria
  • PCR test useful

Question 9

Management of bacterial meningitis: Neonates/Infants

Answer 9

• Ampicillin AND
• Cefotaxime

Question 10

Management of bacterial meningitis: Children & Adults (3 mo. - 50 yrs)

Answer 10

• Ceftriaxone OR
• Cefotaxime AND Vancomycin

Question 11

Management of bacterial meningitis: Adults > 50 yrs.

Answer 11

• Ceftriaxone OR Cefotaxime AND
• Vancomycin AND
• Ampicillin

Question 12

Management of bacterial meningitis: Hospital acquired, recent head trauma/neurosurg, immunocomprom, alcoholics

Answer 12

• Vancomycin AND
• Meropenem
• +/- Ampicillin

Question 13

General management guidelines for bacterial meningtitis

Answer 13

• start antibiotics according to age-group/infection-type
• start corticosteroids before or concurrent w/first dose of antibiotics (prevent complications)
• If LP is delayed for CT/MRI
  
  • STAT blood cultures AND
  • start empiric antibiotics

Question 14

Clinical features of viral meningitis

Answer 14

• headache
• fever
• meningeal irritation
• milder sx than bacterial

Question 15

Diagnostic tests in viral meningitis

Answer 15

• LP ==> CSF profile
  
  • CSF IgM diagnostic of many aroboviruses
• PCR amplification of viral genomic material

Question 16

Viral causes of meningitis

Answer 16

• Common
  
  • Enteroviruses
  • HSV-2
  • Arboviruses (West Nile Virus - WNV)
• Intermediate/Uncommon
  
  • HSV 1
  • EBV
  • VZV
  • HIV
  • HHV-6

Question 17

CSF profile in viral encephalitis

Answer 17

• WBC = 10 - 2,000
• Cell type = mononuclear (lymphocyte)
• Glucose = normal
• Protein = elevated
• Culture
  
  • +/- viral
  • • bacterial
• useful tests: PCR, MRI

Question 18

Viral encephalitis definition

Answer 18

• viral infection of brain tissue (vs. only subarachnoid)
• characterized by signs/symptoms more extensive than meningitis

Question 19

Clinical features of viral encephalitis

Answer 19

• Common: Altered consciousness, fever, and headache.
• Seizures and focal neurological signs/symptoms are common:
  
  • personality change, alteration in mental status/level of consciousness (75-95%)
  • aphasia (65-75%)
  • hemiparesis (30-40%)
  • ataxia (40%)
  • cranial nerve palsies (30-35%)
  • visual field loss (10-15%).
  • Tremors, myoclonus, Parkinsonism seen in WNV.

Question 20

Seasonal prevalences of viral encephalitis

Answer 20

• Summer/Early Fall =
  
  • Arboviruses
• Fall/Winter =
  
  • Lymphocytic Choriomeningitis Virus
• Winter/Spring =
  
  • Mumps
• Any season:
  
  • Herpes Simplex

Question 21

Diagnosis of viral encephalitis

Answer 21

• CSF profile
• EEG abnormalities (60-90%)
• CT & MRI can help identify focal encephalitis
• PCR amplification of viral nucleic acid from CSF is the diagnostic procedure of choice for HSV, VZV, CMV, EBV, and enteroviruses.
• Detection of WNV IgM in CSF is diagnostic of WNV encephalitis and more sensitive than PCR