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Bacteriology > Bacterial Meningitis > Flashcards

Bacterial Meningitis Flashcards

1
Q

What is meninges?

A
  • the membrane that envelops the central nervous system (brain and spinal cord)
  • includes the pia mater, arachnoid mater and dura mater
  • cerebral spinal fluid is between the arachnoid and pis mater
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2
Q

what is meningitis?

A
  • an infection of the meninges
  • usually due to viral or bacterial infection
  • viral meningitis is generally less severe and usually resolves without specific treatment
  • bacterial meningitis can be rapid and life-threatening
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3
Q

What is the blood-brain barrier

A
  • a protective cellular structure that restricts the passage of chemicals, toxins, and microorganisms from the blood to the central nervous system
  • protect CNS from the peripheral immune system
  • endothelial cells are stitched together by structures called “tight junctions”
  • astrocytes and pericytes provide support
    for other cells of the CNS including the BBB
  • microglia cells are the “tissue macrophages” of the CNS
  • white blood cells and antibodies are not normally present in the CNS
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4
Q

What does infection look like for bacterial meningitis?

A
  • nasopharyngeal colonization
  • invasion into blood
  • multiplication in blood
  • the crossing of the BBB
  • invasion of the meninges
  • production of proinflammatory cytokines/chemokines
  • recruitment of leukocytes into CNS
  • edema increased cranial pressure
  • inflammation
  • neural damage
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5
Q

How to traverse through the BBB

A

Transcellular traversal
- through endothelial cells

Paracellular transversal
- force between endothelial cells

Trojan horse mechanism
- an infected macrophage passes through endothelial cells

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6
Q

What is bacterial meningitis?

A
  • rare and very dangerous
  • death in days
  • early signs may be non-specific
  • in an outbreak, 1st people to develop disease are most at risk
  • morality rate is high
  • survivors may have irreversible damage
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7
Q

What type of irreversible damage can survivors have when recovering from bacterial meningitis

A
  • brain damage
  • blindness
  • hearing loss
  • learning disabilities
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8
Q

What are the 4 main clinical symptoms in children and adults

A
  • high fever
  • severe headache
  • stiff neck
  • confusion
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9
Q

What are the clinical symptoms in infants?

A
  • can be subtle, variable and non-specific
  • fever
  • constant crying
  • excessive sleepiness or irritability
  • poor feeding
  • inability to maintain eye contact
  • a bulge in the soft spot on top of baby’s head
  • stiffness in body and neck
  • skin rash in cases of meningococcal meningitis
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10
Q

What are some of the risk factors of bacterial meningitis?

A
  • lack of vaccination
  • young age (infants)
  • living in a community setting
  • uni dorms
  • military personnel
  • boarding schools
  • child care facilities
  • prisons
  • immunocompromised individuals due to disease or chemotherapy
  • cranial surgery
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11
Q

Diagnosis of bacterial meningitis

A
  • history and symptoms
  • blood test for inflammatory markers
  • lumbar punction
  • imaging
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12
Q

Lumbar punction

A
  • cloudy CSF
  • gram stain and culture
  • presence of white cells
  • low glucose
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13
Q

What are some of the physical signs for bacterial meningitis?

A
  • Nuchal rigidity
  • Brudzinski’s sign
  • Kernig’s sign
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14
Q

What is nuchal rigidity?

A

The inability to flex the head forward

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15
Q

What is Brudzinski’s sign?

A

Severe neck stiffness causes a patient’s knees to flex when the neck is flexed

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16
Q

What is Kernig’s sign?

A

Severe stiffness of the hamstrings causes an inability to straighten the leg when the hip is flexed to 90 degrees

17
Q

Treatments for bacterial meningitis

A
  • must be sought immediately
  • intravenous antibiotics
  • corticosteroids to reduce swelling in the meninges
  • supportive therapies (monitoring O2, fluids, etc.)
18
Q

What are the major causes of bacterial meningitis?

A
  • Neisseria meningitidis
  • streptococcus pneumoniae
  • Haemophilus influenzae
  • listeria monocytogenes
  • streptococcus agalactia (in infants)
  • group B streptococcus
  • these diverse pathogens (except listeria) produce a capsule as a major virulence factor
19
Q

Capsules as vaccines?

A

effective host response against capsules in the generation of antibodies from B cells that recognize the capsule

  • antibodies recognize capsule and promote opsonization and phagocytosis
  • polysaccharide vaccines do not provide long-term memory (T cell-independent)
  • T cells respond to proteins/polypeptides not sugars
  • conjugate vaccines have polysaccharide conjugated to protein carriers
  • this vaccine will be T- cell-dependent
20
Q

Neisseria meningitids “meningococcus”

A
  • gram-negative, diplococcus
  • human-specific pathogen
  • colonizes the throat and nose
  • a symptomatic carriage is common
  • produces a polysaccharide capsule
  • antigenic variants (serotypes)
  • A, B, C, W135 and Y
  • a leading cause of bacterial meningitis and also meningococcemia
  • termed invasive meningococcal disease
  • this infection is highly contagious and may cause local epidemics in college dorms, boarding schools and on military bases
21
Q

Meningococcal disease

A
  • meningitis occurs after bacteria enter the bloodstream and cross BBB
  • endotoxin (LPS) can lead to septic shock
  • disseminated intravascular coagulation
  • widespread blood clotting
  • ischemia
  • clotting factors are used up which leads to small skin bleeds
  • purpuric rash
  • the rash does not fade under pressure (“glass test”
22
Q

Vaccines for meningococcus

A
  • Menactra/menveo - quadrivalent conjugate capsule vaccine from 4 serotypes of meningococcus
  • serogroup B most common for invasive disease in Canada but the capsule is poorly immunogenic
  • Bexsero contains 4 recombinant protein antigens
23
Q

What is the African Meningitis Belt

A
  • highest burden of the disease in the world

- mostly caused by serogroup A

24
Q

Streptococcus pneumoniae “pneumococcus”

A
  • Gram-positive cocci that grow in chains
  • commonly reside asymptomatically in the nasopharynx
  • cause pneumonia, ear infections, sinusitis and other diseases
  • a leading cause of bacterial meningitis in children
  • produces a polysaccharide capsule
  • many different serotypes exist
  • a major global pathogen
25
Q

Vaccines for pneumococcus

A
  • has been licensed for use in Canada
  • previously a 7 serotype vaccine
  • now Prevnar 13
  • a conjugate capsule vaccine from the 13 most prevalent serotypes of pneumococcus
  • use of the vaccine is associated with decreasing rates of invasive pneumococcal disease all around the world
  • 23 valent polysaccharide vaccine for high-risk adults, but poorly immunogenic in children (T-cell-dependent)
26
Q

Haemophilus influenzae type b “HiB”

A
  • gram-negative, coccobacillus, produces a polysaccharide capsule
  • primarily causes meningitis in children under 5
  • when it occurs, it tends to follow an upper respiratory infection, ear infection or sinusitis
  • Hib conjugate vaccine available as part of the routine childhood immunization schedules has reduced 99% of invasive Hib disease to low levels
  • H. influenzae type b was the leading cause of bacterial meningitis
27
Q

Listeria monocytogenes

A
  • Gram-positive rods
  • not your ‘typical’ meningitis pathogen
  • a foodborne pathogen
  • “listeriosis” can range from gastroenteritis -> bacteremia -> meningitis
  • high rates of mortality in immunocompromised individuals including neonates and the fetus
  • can grow at 4 degrees Celcius
  • this is important for a foodborne pathogen
  • listeria invades intestinal epithelial cells and replicates within the cytosol
  • listeria makes up less than 5% of meningitis cases
28
Q

Streptococcus agalactiae “Group B streptococcus”

A
  • Gram-positive cocci and grows in chains
  • produces a capsule
  • many women carry S. agalactiae in the urogenital tract as a commensal
  • GBS can be passed from mother to infant during labour
  • women are usually tested for GBS at 36 weeks
  • women who are positive may be treated with antibiotics during labour to prevent infection of the newborn

Bacteriology (8 decks)

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