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Flashcards in Bacterial Infections of CNS Deck (30):
1

Which menigeal layers become inflamed during bacterial infection?

pia mater and the arachnoid

2

List the primary pathogens of bacterial meningitis (4):

  1. Group B Streptococcus
  2. Streptococcus pneumoniae
  3. Neisseria meningitidis
  4. Haemophilus influenza

3

List the occasional pathogens of bacterial meningitis (7):

  1. Listeria monocytogenes (> 50 years of age)
  2. Escherichia coli and other Enterobacteriaceae
  3. Staphylococcus aureus
  4. Nocardia
  5. Mycobacterium tuberculosis (AIDS associated)
  6. Borrelia burgdorferi, Leptospira, Treponema pallidum
  7. Brucella

4

  1. Brain damage during meningitis is mostly attributable to .... 
  2. Bacteria like Streptococcus pneumoniae cause that leads to tissue damage?
  3. Problem, early signs of meningitis can resemble the symptoms of: 
  4. What is the key to curing infections?

  1. Brain damage during meningitis is mostly attributable to the side effects of the host’s own inflammatory response
  2. Bacteria like Streptococcus pneumoniae activate leucocytes
    • release proteolytic enzymes and reactive oxygen species 
  3. Problem, early signs of meningitis can resemble the symptoms of:
    • influenza
    • altered mental status (confusion)
  4. Key: rapid diagnosis

5

Bacteria that cause CNS infection in:

Premature babies and newborns up to 3 months old

  • group B streptococci
    • inhabit the vagina
    • mainly a cause during the first week of life
  • Escherichia coli
    • normally inhabit the digestive tract
    • carry the K1 antigen
  • Listeria monocytogenes

6

Bacteria that cause CNS infection in: 

Older Children

  • Streptococcus pneumoniae
  • Neisseria meningitidis
  • Haemophilus influenzae type B
    • in countries that do not vaccinate

7

Bacteria that cause CNS infection in: 

Adults

  • Streptococcus pneumoniae and Neisseria meningitidis together 
    • 80% of bacterial meningitis cases
  • Listeria monocytogenesis a risk in the elderly > 50 years

8

Which of the primary bacterial pathogens of the CNS does not have a vaccine? 

Group B Streptococcus
(agalactiae)

9

  • Most capsules are composed of ___________
  • __________ antibodies prevent host cell phagocytosis

  • Most capsules are composed of polysaccharides
  • Anti-capsule antibodies prevent host cell phagocytosis

10

H. influenzae 

  • How many serotypes are there? 
  • Which one causes virtually all invasive infections? 
  • What plays a role in protection from infection?

  • 6 serovars
  • Virtually all invasive infections are due to type b H. influenzae (Hib)
  • Antibodies to this polyribosylribose phosphate capsular antigen play a role in protection from infection by Hib

11

Describe the immunity to Hib:

  • Good relationship between age & susceptibility
  • Children < 3 month, maternal Abs are protective
  • Most invasive disease occurs between 3 month and 3 years of age
  • Children under 3 years of age show a humoral immunodeficiency to Hib
  • Children older than 3 years of age develop bactericidal
  • Ig to Hib (vaccination/non-clinical exposure)

12

What is the correlation between Hib meningitis and antibody titers?

Good correlation – incidence meningitis and antibody titers to the Hib capsule

  • i.e. Incidence ↓ as antibody titer ↑

13

What was the problem with the 1st generation Hib vaccine?

Purified capsular polysaccharide

  • Polysaccharides are:
    1. poor immunogens
    2. stimulate T-independent Ab
    3. poor immunologic memory

14

What is the composition of the 2nd generation Hib vaccines?

PRP protein conjugates

15

Polysaccharide-conjugate vaccines stimulate a ....

T-cell dependent antibody response and a memory response

16

Neisseria meningitidis

  • Gram stain 
  • Type of pathogen 
  • Responsible for ...

  • Gram (-) diplococci
  • Intracellular, human-specific pathogen
  • Responsible for septicemia and meningitis

17

Neisseria meningitidis

3 Virulence Factors

  1. Lipooligosaccharide:
    • component of the outer membrane (endotoxin) which stimulates TLR system
      • fever, septic shock, and hemorrhage due to the destruction of red blood cells
  2. Polysaccharide capsule:
    • prevents host phagocytosis
    • evasion of host immune response
  3. Fimbriae 
    • mediate attachment of the bacterium to cells of the nasopharynx

18

Neisseria meningitidis

Diagnosis 

  • Gold standard is to isolate Nm as Gram negative diplococci from cerebrospinal fluid (CSF)
    • Culture CFS on chocolate agar plate
  • Polymerase chain reaction (PCR) may also be sued to identify Nm

19

  • What is the fatality risk for Nm?
  • What should be done for patients with confirmed Nm?

  • Fatality risk approaches 15% within 12 hours of infection, so initiate testing as quickly as possible, but do not to wait for the results before initiating antibiotic therapy
  • Persons with confirmed Nm infection should be hospitalized immediately for treatment with antibiotics

20

Is Nm tranmissable?

Nm can be transmitted 

  • so contacts of the infected patient over the 7 days before onset should receive antibiotics to prevent secondary infections, especially young children

21

What are the serogroups of Nm and what vaccines have been developed for them?

  • Nm comprise ~13 clinical serogroups classified by polysaccharide capsule
  • 6 serogroups 
    • A, B, C, Y, W135 and X
    • responsible for virtually all cases in humans
  • Meningococcal conjugate vaccine (MCV4)
    • preferred vaccine for < 55 years of age
  • Meningococcal polysaccharide vaccine (MPSV4)
    • only meningococcal vaccine licensed for people > 55 (elderly)

22

What are the 2 general classifications of Streptococci?

  1. β-hemolytic streptococci
    • classified by Lancefield grouping
  2. α-hemolytic and γ-hemolytic streptococci 
    • classified by biochemical testing
    • a-hemolytic are referred to as viridans streptococci
      • green pigment formed by the partial hemolysis of blood agar

23

Describe how Streptococci are classified based on hemolysis and cell wall components:

  • Hemolysis when grown on blood agar plates measure lysis of blood cells
    • β clear (complete lysis)
    • α green (partial lysis)
    • γ none (no lysis)
  • Groups based on cell wall components = Lancefield typing scheme
    • Group A = Streptococcus pyogenes (β hemolytic)
    • Group B = Streptococcus agalactiae (β hemolytic)
    • S. pneumoniae = No Lancefield group (α hemolytic)

A image thumb
24

Streptococcus pneumoniae

  • Gram stain 
  • Shape

  • Elongated gram (+)
  • cocci arranged in pairs (diplococci) and short chains

25

Streptococcus pneumoniae 

Virulence factors

  • Ability to colonize oropharynx (surface protein adhesions)
  • Spread into normally sterile tissues pneumolysin, IgA protease)
  • Stimulate TLR inflammatory response (teichoicacid, peptidoglycan fragments),
  • Evade phagocytic killing (polysaccharide capsule)

26

What can streptococcus pneumoniae cause?

  • pneumonia
  • sinusitis and otitis media
  • meningitis
  • bacteremia

27

What are the two Pneumococcal vaccines?

  1. PCV13
  2. PPSV23

28

What are the CDC recommendations for Pneumococcal vaccination? 

  • Infants and Children younger than 2 Years of Age
    • PCV13 is given to infants as a series of 4 doses, 
  • Children 6 through 18 and older
    • Vaccinate with conjugate vaccine
  • Adults 65 years of age and older (elderly)
    • Vaccinate with PPSV23 vaccine

29

Group B streptococcus,
Streptococcus agalactiae

  • Gram stain and classification 
  • Location of inhabitance 
  • Disease

  • Gram positive, beta-hemolytic
    • Lancefield typing scheme Group B
  • Common inhabitant of pharynx, vagina
  • Neonatal infections, meningitis

30

What is the treatment for  Group B streptococcus, Streptococcus agalactiae

  • No licensed vaccine
  • Penicillin is the drug of choice as a therapy
    • Selective prophylaxis antibiotics for Group B streptococcus
      • Pre-term infants
      • Early membrane rupture 
      • Previous infant with Group B streptococcal disease