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MICRO 121 > Lecture 19: CNS Infections > Flashcards

Lecture 19: CNS Infections Flashcards

1
Q

Meningitis

A
  • Infection/inflammation of the meninges (protective layer), the protective lining that protects the brain and the spinal cord
  • 70% of meningitis cases occur in the first 5 years of life
  • Bacterial Meningitis: acute, life threatening } occurs early in life -> untreated can be fatal
  • Aseptic/viral meningitis - usually self limiting
  • Clinical symptoms of meningitis include nuchal rigidity (can’t move your head), headache, confusion, drowsiness
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2
Q

Inflammation of the Meninges

A

Presses down on brain when inflamed

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3
Q

Encephalitis

A

Inflammation of brain tissue - most often viral infections

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4
Q

Meningoencephalitis

A

Inflammation of both the meninges and the brain tissues

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5
Q

Pathophysiology of Meninges

A
  • Seeding of the meninges usually occurs from the bloodstream - secondary to bacteremia or viremia
  • Direct inoculation from trauma, neurosurgery or instrumentation
  • Lots of neurotropic viruses
  • Replicating pathogens that lead to an increase in intracranial pressure (ICP), worsening brain edema and decreasing cerebral blood flow (CBF)
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6
Q

Bacterial Meningitis in Neonates (<1yr old)

A
  • Highest risk for bacterial meningitis due to an immature immune system
  • Difficult to diagnose - general sign and symp are often diff to interpret, alertness, feeding/vomiting, fever
  • Impact - blindness, hearing loss, development delays and even death
    Most common: Streptococcus agalactiae (Group B Strep)
    Others to think about: Listeria monocytogenes, Escherichia coli (inhibits gut)
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7
Q

Bacterial Meningitis in Children

A

Streptococcus pneumoniae (part of normal flora), Haemophilus influenzae (less common), all vaccines that are highly efficacious - so not seen as often as before
- Children carry what makes them sick
- Typically affects un-immunized children, the elderly and/or immunocompromised

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8
Q

Above belt

A

Gram +’ve

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9
Q

Below belt

A

Gram -‘ve

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10
Q

Bacterial Meningitis in Adults

A
  • Vaccine preventable - rare
  • Most often in the immunocompromised and elderly
  • Typically seeds from blood or injury
    Most common: Streptococcus pneumoniae, Neisseria meningitidis
    Less common: Listeria monocytogenes (bc of immune response decrease, moreso with elderly)
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11
Q

Streptococcus agalactiae - Group B Streptococcus (GBS)

A
  • Vaginal carriage rates ~ 30-40%
  • Incidence of about 1 case per 1000 births
  • Less than 1% of full-term babies that become carriers of GBS and can develop meningitis (also pneumonia and/or bacteremia)
  • Early onset - <7 days post birth - detected via prenatal screens at 35 weeks;
  • Late onset 8-30 days
  • Antimicrobial helps with early onset, not late
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12
Q

Escherichia coli (E. coli)

A
  • E. coli is the second most common cause of bacterial meningitis in newborns
  • E. coli causes between 25-33% of cases of meningitis in newborns, but less than 2% of cases of meningitis at all other ages
  • Highest colonizer of the GI tract
  • Acquired via the vaginal canal during birth
  • Premature and low-birth weight babies are at higher risk of E. coli meningitis than full term newborns
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13
Q

Listeria monocytogenes in infants

A
  • Gram +’ve bacilli
  • Environmental sources such as soil, dust, animals, and some foods (soft cheeses, processed meats)
  • Most infections occur after oral ingestion, with access to the systemic circulation after intestinal penetration
  • Intrauterine infections: Transplacental transmission following maternal bacteremia
  • Risk of neonatal disease in vaginally colonized mothers
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14
Q

Listeria monocytogenes Adults: elderly or immunocompromised

A
  • Sporadic cases in adults - about 3 +’ve cases at KGH over last 3 yrs (very low levels acc seen)
  • Much more common amongst the immunocompromised and or elderly patients
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15
Q

Haemophilus influenzae (type B)

A
  • Late 1970’s was the most common cause of meningitis
  • Highest rate of HiB carriage was in infants 6-18 months of age
  • In 1992, the HiB vaccine was introduced
  • Vaccine initiated at 2 months
  • HiB is now very rare in Canada
  • We don’t screen for very rare
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16
Q

Streptococcus pneumoniae

A
  • Most common
  • 40% of ppl carry Streptococcus pneumoniae, starting in the 1st yr of life (carriage in nose and throat)
  • Sporadic cause of meningitis in children and adults
  • Children under 2, and elderly are high risk
  • Low rates of pneumococcal meningitis
  • Vaccine @ 4 months also given to elderly
  • Incidence of S. pneumoniae invasive disease is decreasing as a result
17
Q

Neisseria Meningitidis

A
  • Carriage in nose and throat of 10-20% of teen and adults
  • High rates of colonization common in undergrads in young students, prisons, etc (places w high concentrations of ppl)
  • Most common cause of bacterial meningitis
  • High risk in under 5
  • Sporadic vs. epidemic (schools, colleges, military)
  • 250-750 cases of meningococcal disease occur every year in Canada (sporadic outbreaks/cases)
  • Antibiotic prophylaxis for “close contacts” of ppl
18
Q

lab diagnosis of bacterial meningitis (results)

A
  • antibiotics
  • bacteria metabolize sugar: so low sugar levels (<40 mg / dL)
  • high levels of protein (>250 mg / dL)
  • CSF space -> neutrophils (high levels -)
  • opening pressure elevated
19
Q

lab diagnosis of viral meningitis

A
  • antiviral
  • can’t metabolize so normal or high glucose levels (40-85 mg / dL)
  • No protein (doesn’t produce it)
  • CSF space = lymphocytes (high numbers - WBC < 100 x 106 / L)
  • opening pressure normal
20
Q

lab diagnosis of fungal meningitis

A
  • glucose same as bacteria - eat sugar so low levels (<40 / dL)
  • moderate to high protein, but not as high as bacteria protein (25-500 mg / dL)
  • opening pressure variable
  • predominance of lymphocytes
21
Q

lab diagnosis of bacterial meningitis (what tests)

A

1 thing you do is blood culture (where is it coming from)

  • CSF cell count and differential (stuff from results portion)
  • gram stain (morphological ID of the organisms) can be used to help inform antimicrobial choice
  • bacterial culture
  • PCR for culture negative cases
22
Q

lab diagnosis of fungal meningitis (what tests)

A

cryptococcus neoformans (massive capsule); yeast w a large cap
- meningitis / meningoencephalitis
- more common in T cell immunocompromised: lymphoma, AIDS, steroids
- less aggressive infection that bacterial
if not treated high mortality

23
Q

lab diagnosis for C. neoformans meningitis

A
  • culture (24-48hrs)
  • latex agglutination
  • if present, neoformans will bind to the latex beads and visible agglutination will occur
24
Q

description of viral meningitis

A
  • milder than bacterial meningitis w death or permanent brain damage being very rare
  • self limiting in majority of cases
  • 1/2 of all cases are caused by enteroviruses
25
Q

enteroviruses

A
  • results in self limiting meningitis most of the time
  • asymp or fairly non specific
  • most common in summer and late fall
  • fecal-oral transmission or direct contact w resp secretions
    (poliovirus, echovirus, coxsackie A and B)
26
Q

poliovirus - FYI

A
  • most asymp
  • paralytic poliomyelitis (irreversible) most serious manifestations (asymm flaccid paralysis that affects spinal cord not brain)
  • major in developing countries -> lack of vaccine distribution, global polio eradication,
  • uses inactivated polio virus
27
Q

w viral meningitis how accurate is the virus culture

A

only +’ve in 50% of viral meningitis cases
- PCR for enteroviruses

28
Q

encephalitis description

A
  • no or mild symptoms
  • serious cases: nausea/vomit, headache, fever, confusion, drowsiness
  • Urgent symptom is altered level of consciousness
  • you need crows, mosquitoes for west nile (no human transmission)
  • HSV, enteroviruses, arboviruses
29
Q

herpes encephalitis

A

HSV-1 is most important cause of fatal sporadic encephalitis (fatal if not treated)
- brain infection thought to occur by direct neuronal transmission
- factors that precipitate this infection are unknown

30
Q

arbovirus encephalitis

A

geo distribution
- west nile**
- eastern equine encephalitis
- western equine encephalitis
- st louis encephalitis
- japanese encephalitis

31
Q

west nile virus

A
  • seasonal incidence in North America, also in Africa, Middle East, Europe, Russia, India, and Indonesia
  • mild sympt, disease can be severe
32
Q

lab diagnosis of encephalitis

A
  • clinical sympt - 1st screen
  • PCR testing
  • Antibody detection in serum (serology)
33
Q

brain abscess etiology

A
  • direct trauma or accident or through hematogenous spread from blood
  • direct extension from the sinuses
  • tend to be polymicrobial (aerobic and anaerobic bacteria)
  • drained surgically, antibiotics do not penetrate absess

MICRO 121 (19 decks)

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