(I) Gram Negative Cocci - (3) * Neisseria species overview

Question 1

2 main species of gram negative Cocci:

[…]

Answer 1

2 main species of gram negative Cocci:

1. Moraxella - catarrhalis, others.
2. Neisseria - meningitidis, gonorrhea

Question 2

Characterize (4) : Neisseria spp.

Answer 2

(1) Gram (-)** di**plococci
(2) Oxidase (+)
(3) Fimbriae
(4) IgA protease

(Also catalase (+))

Question 3

Name 2 culture mediums used for Neisseria spp.

Answer 3

(1) Chocolate agar
(2) Thayer-Martin (VPN)

V stands for vancomycin, which kills gram-positive organisms .
**P **stands for polymyxin (colistin) which kills all gram-negative organisms (except Neisseria).
N stands for nystatin, which eliminates fungi.

Question 4

What antibiotics is Thayer-Martin agar enriched with?

Answer 4

(1) Vancomycin
(2) Polymyxin
(3) Nystatin

Question 5

Name an immunodeficiency which associated with increased susceptibility to Neisseria spp.

Answer 5

C5-9 deficiency

Question 6

Why is Neisseria spp. so effective at evading the immune system?

Answer 6

Antigenic variation

(Of the pili. Also IgA protease)

Question 7

Name 2 organisms with IgA proteases

Answer 7

(1) Neisseria spp.
(2) Strep. pneumoniae

(Although not included in the sketch, Haemophilus also has it)

Question 8

Oxidase test tests for […]

Answer 8

Oxidase test tests for bacteria that can use oxygen.

The oxidase test is used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain. (note: All bacteria that are oxidase positive are aerobic, and can use oxygen as a terminal electron acceptor in respiration. This does NOT mean that they are strict aerobes.