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CNS Infections


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Most common causes of Acute Bacterial Meningitis in: birth-4 weeks
1. Group B Strep
2. E. coli
3. Listeria
Most common causes of Acute Bacterial Meningitis in: 4 weeks - 15 years
1. S. pneumoniae
2. N. meningitidis
3. H. influenza Type B
Most common causes of Acute Bacterial Meningitis in: 15 years - 30 years
1. N. meningitidis
2. S. pneumoniae
Most common causes of Acute Bacterial Meningitis in: 30 years - 50 years
1. S. pneumoniae
2. N. meningitidis
Most common causes of Acute Bacterial Meningitis in: > 50 years
1. S. pneumoniae
2. Listeria
3. Enteric GNR
Bacterial causes of meningitis
h. influenzae
enteric GNR
Group B Strep
Aseptic causes of meningitis
Clinical Presentation of Meningitis
fever, headache, nuchal rigidity, nausea/vomiting, drowsiness, confusion, seizures, cranial nerve palsies, papilledema
Pathogenesis of Meningitis
1. Upper resp tract colonization --> bacteremia
2. direct inoculation: congenital defects, trauma, surgery, parameningeal focus with rupture
3. retrograde access via neuron: Rabies/Herpes
Dx of Meningitis
If Acutely Ill:
Blood culture, start abx (dont wait), THEN LP
If Stable:
LP, blood culture, start abx
Lab Tests for Meningitis on CSF
Gram Stain
India Ink Stain
Latex Agglutination
Counter Immuno Electrophoresis
What is India Ink Staining?
use it to visualize the yeast Cryptococcus, gets black outline
What is Latex Agglutination?
Agglutination of latex particles coated with specific antibody in presence of polysaccharide antigen in CSF. Use it to detect capsular polysaccharides.
Meningitis Predisposition:
outbreaks in close populations (military/college dorm)
Meningitis Predisposition:
recent head trauma (esp w/ nasal CSF leak)
Meningitis Predisposition:
Group B Strep, E. coli, Listeria
colonize vagina and infect neonate at birth
Meningitis Predisposition:
S. Epidermis
ventricular/peritoneal shunt
Meningitis Predisposition:
Cryptococcus and Listeria
Meningitis Predisposition:
Gram Negative Rods
Differential Diagnosis for Meningitis
aseptic meningitis
brain abscess
subdural/epidural empyema
viral encephalitis
Meningitis Chemoprophylaxis
Meningococci: Ciproflaxin/Rifampin
H. Influenzae: Rifampin
Meningitis Vaccines:
meningococcus: vaccine w/ serotypes A, C, Y, W-135
pneumococcus: 23 serotype unconjugated vaccine or 7 serotype conjugated vaccine
h. influenzae: capsular poly B conjugated vaccine
Causes of Brain Abscess
oral flora: viridans, anerobes (bacteroides, fusobacterium, peptostreptococcus)
Listeria, Nocardia, Actinomyces
Brain Abscess Clinical Picture
prolonged fever, headache, altered mental status, similar to other space occupying lesions
Diagnosing Brain Abscess
blood culture
culture/stain pus from abscess
Brain Abscess Therapy
3G Cephalosporin plus metronidazole
Viral Meningitis Causes:
Enteroviruses (coxasackie, echoviruses)
Viral Meningitis Diagnosis:
CSF tests for protein, sugar, cells
failure to find bacteria on stain/culture
viral cultures
rise in AB titer (retrospective)
Causes of Viral Encephalitis
non-neonates: 70% unknown, HSV-1, Arboviruses
neonates: HSV-2
Diagnosis of Herpes I Encephalitis
PCR CSF, treat with acyclovir
Post Infectious/Post-Vaccination Encephalitis
varicella, MMR, H flu B
Acute Flaccid Paralysis causes:
Poliovirus, coxsackie, echo, west nile, guillain barre

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