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Neuro Part I > Bacterial Meningitis > Flashcards

Bacterial Meningitis Flashcards

1
Q

Infections of the Brain

A

brain parenchyma = encephalitits, abcess

meninges = meningitis

spinal cord = myelitis

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2
Q

Meningitis - Definition

A
  • inflammation of the meninges
  • exudative response seen in CSF
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3
Q

Meningitis - Categories

A
  • infectious causes
    • bacteria, viruses, fungi
  • non-infectious causes
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4
Q

Bacterial Meningitis - Risk Factors

A
  • age - v. young and v. old
  • immunocompromised
  • basal skull fracture, head trauma, post-neurosurgery, cerebrospinal fluid shunt
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5
Q

Causes of Bacterial Meningitis in the US

A
  1. Streptococcus Pneumoniae (adults)
  2. Neisseria Meningitides (teens, colleges)
  3. Group B Streptococcus (newborns!)
  4. Haemophilus Influenzae Type B* (infants!)
  5. Listeria Monocytogenes

*Hib is the most common cause of bacterial meningitis in the developing world where children are not vaccinated.

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6
Q

Causes of Bacterial Meningitis by AGE

A

Newborn

  • **Gp B Strep, **E. Coli, Listeria Monocytogenes

Infants

  • Neisseria Meningitidis, Hib, Strep Pneumoniae

Children

  • Neisseria Meningitidis*, Strep Pneumoniae
  • *teens, colleges, etc

Adult

  • **Strep Pneumoniae, **N. Meningitidis, mycobacteria
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7
Q

Bacterial Meningitis - Pathogenesis

A
  1. Hematogenous delivery of bacteria to SAS.
  2. Host immune response.
  3. Edema, increased intracranial pressure.
  4. Decreased cerebral bloodflow.
  5. Damage, seizures, herniation.

Injury and direct delivery of bacteria is less common.

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8
Q

Bacterial Meningitis - Symptoms

A

In neonates - temperature instability and lethargy.

Sudden onset…

  • fever
  • headache
  • stiff neck

Often accompanied by…

  • ​ nausea, vomiting
  • photophobia
  • altered mental status, confusion
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9
Q

Bacterial Meningitis - Diagnosis

A

Examination of CSF via

  • cell count
  • gram stain
  • antigen tests
  • *culture - gold standard
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10
Q

CSF Findings in Acute Bacterial Meningitis

A

WBCs >1,000/mm3 (very high)

Cells PMNs (note - lymphocytes in viral, fungal)

Protein mild to marked elevation

Glucose normal to marked decrease

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11
Q

Streptococcus Pneumoniae

  1. ID
  2. Causes?
  3. Virulence
  4. Vaccine?
A
  • Gm + diplococci, lancet-shaped
  • catalase –
  • alpha hemolytic
  • optochin sensitive
  • bile soluble

pneumonia, bacteremia, meningitis, otitis media

virulence - capsule, multiple types

vaccine - 13 valent conjugate, 23 valent polysaccharide only

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12
Q

Neisseria Meningitidis - Morphology & ID

A

Gm – diplococci (only one!)

Oxidase +

  • cytochrome C oxidase reduces dye to **blue color **

Aerobic, grows on chocolate agar w/ hemin, NAD+

  • glistening colonies = capsule!
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13
Q

Neisseria Meningitidis - **Key **Virulence

A

antiphagocytic capsule

  • interferes w/ complement deposition
  • prevents C3b-mediated uptake of meningococci by phagocytes

Recall that N. meningitidis is gm –. Ab deposition in presence of complement can also lead to cell lysis in addition to phagocytosis.

12 serogroups/types

  • US - Gp B and C

(type B capsule cross-reacts w/ E. coli K-1 capsule)

  • Africa - Gp A and W-135
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14
Q

Neisseria Meningitidis - Other Virulence

A

LOS (as opposed to LPS)

  • released blebs of lipid A + sugar are toxic

Protease that cleaves sIgA1 (secretory IgA)

Capsule, IgA protease, and serum resistance allow it to survive in the bloodstream. Pili allow it to attach to the BBB; LOB causes BBB inflammation and mediates entry into CNS.

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15
Q

Neisseria Meningitidis - Clinical Signs and Symptoms

A

MOST COMMON CAUSE IN TEENS, COLLEGES

  • 5-10% are asymptomatic pharyngeal carriers (esp in closed populations, ie. military barracks)
  • meningococcemia (meningococci in blood)
    • petechiae, purpura
    • Waterhouse-Friderichsen Syn (shock, DIC, bilateral destruction adrenal glands)
    • meningitis
    • chronic recurring meningococcal disease
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16
Q

Neisseria Meningitidis - Pathogenesis

A

Exposure -> colonize URT -> evades PMNs -> invades mucosa -> meningococcemia ->

  1. no clinical manifestations -> recovery
  2. Waterhouse-Friedrichsen Syn -> recovery, death
  3. meningitis and/or cutaneous manifestations -> recovery, death
17
Q

Neisseria Meningitidis - Epidemiology

A

Spread = human to human

Age = greatests in 6 mo to 3 yrs unvaccinated

Serogroups - incidence varies with serogroup and location.

*Gp A causes epidemics in less developed nations.

US - Gp B > Gp C (we have a Gp C vaccine, we are just getting a Gp B vaccine)

18
Q

Neisseria Meningitidis - Vaccine

A

MenACWY-D or MenACWY-CRM

  • tetravalent conjugate vaccine
  • contains capsular polysaccharide from A, C, Y, and W135 conjusted to diphtheria toxoid
  • @ age 11-12 yrs, 1 dose (1 booster recommended if first dose given before 16 yrs)

MCV4 (multivalent) recommended for

  • v. young or v. old at risk
  • microbiologists
  • college freshmen, military recruits
  • travelers
  • persons with complement deficiency
19
Q

Group B Strep (GBS) (aka Streptococcus agalactiae)

Clinical Course and Prevention

A

MOST COMMON CAUSE IN NEONATES

  • Why? Normal flora in gut and transient vaginal flora in 10-30% of pregnant (and non-pregnant) women.
  • Can cause respiratory tract infections or septicemia that can progress to meningitis.
  • Prolonged labor after rupture of membranes increases transmission risk.
  • Also causes meningitis in pregnant or post-partum adults due to bacteremia.
  • Can also occur in non-pregnant adults; usually elderly or individuals with chronic disease.

Prevent via administration of penicillin G I.V. during labor.

20
Q

Group B Streptococci (GBS) - Morphology and ID

A
  • Gm + cocci in chains, catalase –
  • beta-hemolytic (GAS or GBS)
  • bacitracin insensitive (v. GAS)
  • CAMP test positive (v. GAS)
  • confirm via detection of gp-B specific antigen
21
Q

Listeria Monocytogenes - Clinical Course

A

Food-borne pathogen (e.g. soft cheese, lunch meaths, hot dogs) that can cause

  • miscarriage and stillbirth in pregnant women
  • severe systemic disease in immunosuppressed
  • occasionally, gastroenteritis in healthy persons
22
Q

Listeria Monocytogenes – Morphology & ID

A

widely distributed in nature

psychrophilic – grows in cold temps

mesophilic – grows in moderate temps

Gm + rod, motile, catalase +, beta-hemolytic, CAMP +

facultative intracellular pathogen

23
Q

Listeria Monocytogenes – Virulence, Pathogenesis

A

Facultative Intracellular Pathogen

  1. Produces listerolysin (LLO) that promotes release of the bacteria from phagosomes into the cytoplasm, responsible for hemolytic phenotype.
  2. Multiplies in the cytoplasm; moves w/in cell by a mechanism involving host actin polymerization mediated by ActA produced by L. monocytogenes.
  3. Spreads directly from cell to cell via actin tails without entering extracellular space.

*Infections are terminated by a cell-mediated immune response.

Neuro Part I (8 decks)

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