CNS Infections Flashcards
Describe the pathogenesis of bacterial and viral meningitis
- Nasopharyngeal colonization
- Local invasion
- Bacteremia.. capsule plays big role(in blood)
- Meningeal invasion (carried here by blood!)
- Bacterial replicatoin in the subarachnoid space (no defense against them here… its just a party!!)
- Release of bacerial components (cell wall, LOS)
What 3 things are needed for Meningitis?
Needs a susceptible host… good environment, and a good bug!
Clinical Presentation of Bacterial Meningitis
- Fever
- headache and meningismus
- Mental status change, seizures
- Sometimes a rash happens…Neisseria meningitidis… causes purpura fulminans.. release high levels of endotoxins causes cascade which removes Protein C… you get coagulation that causes purpura!
** Could be on exam Virulence Factors (factors produced by pathogen to help them… in meningitis):
- Attachment pili… attach to nasopharyngeal mucosal surface
- IgA protease… evade host mucosal immune response
- Polysaccharide Capsule… prevent opsonization and complement activation; prevent phagocytosis
- Adhesins… facilitate attachment and crossing the blood brain barrier
- Sub-capsular techoic acid, LPS… stimulate host innate inflammation
Meningitis Risk Factors
- Extremes of age
- Complement deficiency
- Asplenia
- Hypogammaglobulin
- HIV
- Steroids, listeria medications
List the common pathogens that cause bacterial meningitis .Which are encapsulated?
- Strep. Pneuomoniae… encapsulated
- N. Meningitidis… encapsulated
- H. Influenzae…. encapsulated
- Listeria Monocytogenes…
- Other bacters… GBS (group B strep), E. Coli (encapsulated)
Viral Meningitis Definition
Refers to infection of the meninges by a viral pathogen
List the common pathogens that cause viral meningitis
- Enteroviruses, eg. Coxsackie, Echovirus
- Herpes Simplex Type
Syndromes and Microbial Causes of Acute Bacterial Meningitis, Acute Viral meningitis, Sub-acute/Chronic Meningitis, Encephalitis (sporadic), and Encephalitis (geographic)
Acute Bacterial Meningitis: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenza, Listeria monocytogenes
Acute Viral Meningitis: Enterovirus, HSV-2 Sub-acute/Chronic Meningitis: TB Encephalitis(sporadic): HSV-1 Encephalitis (geographic): West Nile Virus
Potential routes of entry for CNS infection:
Hematogenous: Most common route for most microbial pathogens
Contiguous: Extension from bacterial sinusitis or bacterial otitis media
Direct Inoculation: Post neurosurgical Procedure, post trauma
Via Peripheral Nerves: Ex. Herpes virus, Rabies, VZ
Clinical Presentation of Meningitis
- Fever and headache, Meningismus (stiff neck, photophobia, and headache)
Lumbar Puncture basics and values CSF for Bacterial Meningitis
- Get it from Lumbar spine! (go in with need 2 cm!)
- Let it flow, can extend legs to promote flow.
- Protein <40… probably NOT MENINGITIS.. inflammation allows it to cross barrier.. pushes protein across barrier and thus we’ll see it!
- Glucose low… bacteria eating up glucose!
- Usually no WBC’s in CSF! (<5).. in meningitis will have HIGH for septic.. will be MAINLY NEUTROPHILS in BACTERIAL… MOSTLY LYMPHOCYTES IN VIRAL MENINGITIS**
- Send CSF for Cell count and differential, protein and glucose concentration, gram stain and culture, special test
Viral Meningitis Lumbar Tap CSF values
- Protein >40
- Glucose 0.6, normal, nothing eating the sugar
- HIGH WBC count… MOSTLY LYMPHOCYTES
Know the empiric antimicrobial treatment of bacterial meningitis, viral meningitis, and herpes encephalitis
- Acute bacterial Meningitis: Ceftriaxone PLUS vancomycin PLUS dexamethasone PLUS ampicillin, DOSE is higher than usual!
- Viral Meningitis: Supportive.
- Encephalitis: Acyclovir
Can vaccines prevent Meningitis?
Yes! Why are conjugate vaccines given rather than polysaccharide… Poly doesn’t allow T cell stimulation to occur… This is significant because T cells allow adaptive immune system to FORM MEMORY B CELLS!!! And forming very good antibodies not just weak ones!… IgA, IgG… and antibodies which are affinity matched to target cell!!!! Also prevents transmission in a community!!!
