Micro - Gram Negative Cocci

Question 1

This species is positive for the “hockey puck” test

Answer 1

Moraxella catarrhalis

-on blood agar or chocolate agar

Question 2

All species of Neisseria and Moraxella are catalase ___ and oxidase ___

Answer 2

Positive

Positive

Question 3

What do Neisseria and Moraxella look like this under a microscope when gram stained?

Answer 3

Kidney-bean or coffee bean shaped diplococci

• paired cocci with flat sides
• like two domes joined together

Question 4

The CarboFerm rapid ID panel is to confirm the identity of…

Answer 4

Moraxella catarrhalis
-butyrate esterase well turns blue

Neisseria spp
-read carbohydrate wells to ID spp

Question 5

This gram negative organism is often confused as a rod or a cocci…

Answer 5

Acinetobacter

Question 6

N. meningitidis and N. gonorrhoeae - which one is always a pathogen?

Answer 6

N. gonorrhoeae

-meningitidis can be normal flora in some people

Question 7

Can N. gonorrhoeae be detected in blood cultures?

Answer 7

Yes, if it disseminates from genitals

Question 8

Pathogenic Neisseria spp have the ability to produce this virulence factor…

Answer 8

Capsule

Question 9

What are the 3 groups that define pathogenic Neisseria from nonpathogenic Neisseria?

Answer 9

Group 1 = pathogens
-N. meningitidis and N. gonorrhoeae

Group 2 = commensal Neisseria that grow on selective media (MTM)

Group 3 = commensal Neisseria that do not grow on selective media (MTM)

Question 10

Differentiation of different species of Neisseria is based on…

Answer 10

Carbohydrate (sugar) profile

Question 11

Pathogenic Neisseria produce colonies that look… Non-pathogenic Neisseria produce colonies that look…

Answer 11

Shiny/mucoid, smooth

Wrinkled, dried

Question 12

Moraxella can be differentiated from Neisseria based on this reaction…

Answer 12

Butyrate esterase reaction

• blue well on CarboFerm panel
• can also use DNase reactions

Question 13

Moraxella vs Neisseria - which one prefers body temp and which one prefers lower temperature for growth?

Answer 13

Moraxella = 28C

Neisseria = body temp

Question 14

Can Moraxella be ID’d based on carbohydrate reactions?

Answer 14

No, Moraxella is asaccharolytic

-use butyrate esterase CarboFerm reaction

Question 15

Acinetobacter can be differentiated from Moraxella and Neisseria with this rapid test… What is the test result?

Answer 15

Oxidase = negative

-Moraxella and Neisseria are oxidase positive

Question 16

Pathogenic Neisseria are very sensitive. How are blood, CSF, and nasopharyngeal samples processed?

Answer 16

Centrifuged and gram stained

Question 17

Pathogenic Neisseria are very sensitive. How are nasopharyngeal SWABS processed?

Answer 17

Plated on JEMBEC system

-rectangular chocolate agar plate with CO2 generating mechanism

Question 18

Cotton fibers used in transport medium contain toxic fatty acids. How can we neutralize these fatty acids?

Answer 18

Add charcoal to transport medium

• dacron or rayon fibers preferred over cotton
• must be processed within 6-12 hrs
• Stuart’s or Amie’s charcoal transport medium

Question 19

The latex agglutination assay is used to detect this Neisserial antigen in body fluids…

Answer 19

Capsules

Question 20

Neisseria spp usually has better growth on blood agar or chocolate agar?

Answer 20

Chocolate agar

• with increased CO2
• some Neisseria spp (gonorrhoeae) only grow on chocolate
• always use a chocolate plate

Question 21

What is the selective medium of choice to cultivate pathogenic Neisseria and Moraxella from normal flora? What does it contain that makes it a selective medium (2)?

Answer 21

Thayer-Martin medium (MTM)
-modified chocolate agar

Enrichment supplement = IsoVitaLex
Antimicrobials = colistin, vancomycin, nystatin, trimethoprim

Question 22

How many serotypes of Neisseria are there and what are they? Which one is the more virulent?

Answer 22

A, B, C, Y, W135

Most virulent = B

Question 23

Besides MTM, the other selective media for gonorrhea is…

Answer 23

NYC medium

-clear/transparent