(I) Gram Negative Cocci - (2) * Neisseria meningitidis

Question 1

Which species of Neisseria ferments maltose?

Answer 1

N. meningitidis

Question 2

What is the first place N. meningitidis colonizes?

Answer 2

Nasopharynx

Question 3

Which strain of N. meningitidis most commonly causes meningitis?

Answer 3

Type B

Question 4

Differentiate between the vaccine for H. influenzae and N. meningitidis in regards to the contained capsular antigens

Answer 4

(1) H. influenzae: ✔ Type B capsular antigen
(2) **N. meningitidis: ✘ Type B capsular antigen **

Question 5

Name 2 genetic defects which increase your risk for N. meningitidis

Answer 5

(1) C5-9 deficients
(2) **Sickle cell **

Question 6

What organism has LOS instead of LPS?

Answer 6

N. meningitidis

Question 7

Describe the pathogenesis of Waterhouse-Friderichsen syndrome

Answer 7

LOS induced inflammation
⇒ ↑ Vascular permeability
⇒ ↑ Exudation
⇒ ↓ Perfusion
⇒ Reflexive vasoconstriction
⇒ Ischemic adrenals

(WFS can occur due to other organisms, and in that case inflammation would not be due to LOS)

Question 8

What organism is most associated with meningitis with a petechial rash?

Answer 8

N. meningitidis

Question 9

What is Waterhouse-Friderichsen syndrome?

Answer 9

Sepsis ⇒ Hemorrhage of adrenals

Question 10

Treatment: N. meningitidis

Answer 10

Ceftriaxone

Question 11

Prophylaxis: N. meningitidis

Answer 11

Rifampin, ciprofloxacin, ceftriaxone

(For close contacts ≡ Someone who spent ≥ 8 hours with patient in 7 days prior to onset of symptoms)

Question 12

Diagnosis for N.meningitidis is ALWAYS using

[…]

Answer 12

Diagnosis for N.meningitidis is ALWAYS using

Blood (+ CSF + Throat swab + other sites) cultures (depending on clinical presentation)

Also can do
- direct gram stain of CSF
- Molecular diagnosis becoming increasingly important

Note that the diplococci can be seen (Gram stain) or cultured from biopsies of the petechiae.

Question 13

How to differentiate N. meningitidis from N. gonorrhoeae?

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Answer 13

How to differentiate N. meningitidis from N. gonorrhoeae?

N.meningitidis is maltose fermenting

Question 14

Prophylaxis in close contacts of neisseria meningitidis:

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Answer 14

Prophylaxis in close contacts of neisseria meningitidis:

Rifampicin, ciprofloxacin, ceftriaxone

Question 15

Risk factors of Neisseria meningitidis infection include (IMPT!!!)

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Answer 15

Risk factors of Neisseria meningitidis infection include (IMPT!!!)

• Hajj pilgrimage
• travel to African “meningitis belt”
• asplenia/hyposplenism – recommended for vaccinations/prophylactic antibiotics (same as pneumococcus)
• Army recruits
• College freshmen (freshmeningitis)

Question 16

Splenectomy predisposes a person to infection by […] bacteria (pneumococcus and meningococcus)

Answer 16

Splenectomy predisposes a person to infection by encapsulated bacteria (pneumococcus and meningococcus)

some H.influenze strand are encapsulated

If u are damn curious why:
“Our immune system clears encapsulated bacteria by opsonizing them with antibodies and then the macrophages and neutrophils in the spleen (the reticulo-endothelial system) phagocytose the opsonized bacteria. So, patients who have lost their spleens (asplenic), either from trauma or from sickle-cell disease, have difficulty clearing encapsulated bacteria and are more susceptible to these infections”

Question 17

Tell me about meningococcus vaccines (vvvvvvvv IMPT!!!)
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What capsule types are included in the quadrivalent vaccine? (IMPT!)
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Answer 17

Tell me about meningococcus vaccines (vvvvvvvv IMPT!!!)
- Vaccine for N.meningitidis is NOT routine in singapore. Familarize yourself with the National Childhood Immunization Schedule!
- Polysaccharide vaccine NOT effective in infants (same as pneumococcus PPSV23)
- Quadrivalent conjugated vaccines are better. Monovalent vaccines are country specific (C in UK, A in meningitis belt)

What capsule types are included in the quadrivalent vaccine? (IMPT!)
A, C, W135, Y

Group B vaccines are protein based, using combinations of sub-capsular peptides. Its called MenB, but its fairly new and not recommended for routine vaccination.

Question 18

Transmission of Neisseria Meningitidis:

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Answer 18

Transmission of Neisseria Meningitidis:

Close contact (kissing), Respiratory droplets

Cuz carriage is in nasopharynx in 10-15% of people

Question 19

Treatment of Neisseria Meningitidis? (vvv IMPT!!!)

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  AND
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Answer 19

Treatment of Neisseria Meningitidis? (vvv IMPT!!!)

• Ceftriaxone (clears throat carriage, covers major pathogens)
  AND
• Benzylpenicillin (add in case of resistance, also cuz meningitis not small matter)

can be minimalist and use Benzylpenicillin (but does not clear throat carriage)

Tbh the moment u add vanco….the gram positives are all probably all gone case alr.

Question 20

What are the 4 virulence factors in N.meningitidis? (vvv IMPT!!)

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Answer 20

What are the 4 virulence factors in N.meningitidis? (vvv IMPT!!)

• Lipooligosaccharide (LOS, similar to LPS) endotoxin
• Anti-phagocytic capsule (13 serogroups including A,B,C,Y,W-125
• Ig A protease
• antigenic variation
  ))

The LOS causes blood vessel destruction and sepsis –> petechiae

Anti-phagocytic capsule seen in both pneumococcus and meningococcus (and H.influenzae)

Question 21

What is the clinical presentation of Neisseria Meningitidis infection? (vvvvvvvv IMPT!!!)

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Answer 21

What is the clinical presentation of Neisseria Meningitidis infection? (vvvvvvvv IMPT!!!)

1. Meningococcaemia (when meningococcus enters blood stream, may progress to severe state of fulminant meningococcaemia, systemic **inflammatory response syndrome SIRS)**
   - Non-blanching meningococcal rash (disseminated petechiae –> purpura –> ecchymoses on skin & conjunctiva)
   - Haemorrhagic adrenalitis (Waterhouse-Friderichsen syndrome)
2. Meningitis
   - uncommon presentations: pneumonia, pericarditis, endocarditis, conjuctivitis, arthritis, chronic meningococcaemia (intermittent rash)
   - Can develop into fulminant meningococcaemia/meningitis

Non-blanching =blood outside vessels/not hyperraemia = haemorrhagic rash

VERY important card. Meningitis + non blanching rash = N. meningitidis!!

“Meet the 2 pathogenic kidney beans, which have been removed from the microscope slide. They are sitting together at the breakast table. Notice that they sit facing each other, forming a gram-negative dough­ nut-shaped diplococcus. The bean on the left, Neisseria meningitidis , drinks a pot of cofee and becomes very nervous and irritable (central nervous system irritation-meningitis). The other pathogenic kidney bean is Neisseria gonorrhoeae , who is a pervert (notice how he is displaying the latest center-old pin-up). He enjoys hanging out on sexual organs and swimming in “ sexual fluids.” He causes the sexually transmitted disease (STD) gonorrhea.”