Neisseria meningitidis

Question 1

Describe the gram stain appearance on N. meningitidis.

Answer 1

gram negative (pink) diplococcus (always in pairs)

Question 2

Is N. meningitidis part of the normal microflora?

Answer 2

Yes, nasopharynx commensal in many individuals. Can cause disease in e.g. immunocompromised individuals

Question 3

How is N. meningitidis transmitted/reaches site of infection?

Answer 3

inhalation of droplets

Question 4

What are the risk factors for N. meningitis infection?

Answer 4

1. recent viral/mycoplasma upper respiratory tract infection
2. smoking
3. complement deficiency

Question 5

Which 2 serious diseases can N. meningitidis give rise to?

Answer 5

1. meningitis (one of most frequent causes)
2. fulminant meningococcaemia (sepsis) - intravascular coagulation, circulatory collapse and potentially fatal shock

In each case, symptoms can occur with extremely rapid onset and great intensity. Can progress in hrs to death.

Question 6

Describe the management of N. meningitidis infection.

Answer 6

• Antibiotics: ceftriaxone - can penetrate CSF

- Supportive: O2 support, fluid challenge

Question 7

What type of antibiotic is ceftriaxone?

Answer 7

cephalosporin (penicillin/B-lactam)

Question 8

How is N. meningitidis infection diagnosed?

Answer 8

1. Samples from CSF or blood cultured on chocolate agar - gram stain
2. latex agglutination tests with serogroup-specific anticapsular antibody can be used to obtain rapid presumptive identification of serogroup-specific meningococci in CSF

Question 9

How can N. meningitidis infection be prevented?

Answer 9

1. vaccination: MenC conjugate, MenACWY, MenB

2. prophylactic antibiotics

Question 10

What are the N. meningitidis serogroups? Which is most prevalent in the UK?

Answer 10

groups based on polysaccharide capsular antigen - at least 13 serogroups

serogroup B

Question 11

Name 3 N. meningitidis virulence factors.

Answer 11

1. Pili - enhances attachment (e.g. to nasopharyngeal mucosa)
2. Polysaccharised capsule - antiphagocytic and antigenically diverse
3. Lipopolysaccharide endotoxin - stimulates inflammation

Question 12

Describe symptoms of meningococcal meningitis.

Answer 12

1. non-blanching purpuric rash
2. fever
3. headache
4. stiff neck
5. photophobia.
6. confusion, unconsciousness, seizures
7. Shock: tachycardia and/or hypotension, respiratory distress, altered mental state and poor urine output.
8. Kernig’s sign (pain and resistance on passive knee extension with hips fully flexed).
9. Brudzinski’s sign (hips flex on bending the head forward).