Other GNB

Question 1

List the main identifying features of Pasteurella multocida?

Answer 1

• Gram: GNCB (short rod)
• Oxidase pos (slow rxn)
• Catalase pos
• Non-motile
• non-haemolytic
• NG on MAC
• S to Pc

Question 2

why Haemophilus species grow well on CHOC agar incubated in CO2?

Answer 2

bc fastidious and require X (haemin) and V (NAD, NADP) Factor from lysed RBC in CHOC

Question 3

What lab. features/characteristics would indicate that a Haemophilus sp. had been isolated from an ear swab?

Answer 3

• Gram: GNCB
• Grey/transcluscent colonies on CHOC
• Not grow well on BA except growing around other colonies that can release X + V factors (Satellitism)
• NG on selective media e.g. MAC/CLED

Question 4

How could you differentiate (speciate) between the clinically significant Vibrio sp. using TCBS agar and susceptibility to O129 (10ug)?

Answer 4

V. cholerae: Yellow, S
V. alginolyticus: Yellow, R
V. vulnificus: blue/green, S
V. parahemolyticus: blue/green, R

Question 5

Which oxidase Pos GNB grow on MAC without salt? Which don’t?

Answer 5

G on MAC: Aeromonas sp., Plesiomonas sp.

NG on MAC: Vibrio sp., Neisseria so, Haemophilus sp

Question 6

What is the most likely identity of a Haemophilus sp. that requires both X and V factor for growth?

Answer 6

Haemophilus influenzae

Question 7

How would you differentiate between Kingella kingae, Pasteurella multocida and Actinobacillus sp./Aggregatibacter? Hint: use MAC, oxidase and spot indole

Answer 7

MAC: all NG
Catalase: Pasteurella multocida, Actinobacillus sp
Spot indole: Pasteurella multocida 
(Neg all test: Kingella kingae)
* only referring to G or Pos result

Question 8

How could you differentiate between species of Vibrio, Aeromonas and Plesiomonas in the clinical laboratory without using a MALDI-TOF? Discuss the separation of the genera and then the separation/identification within each to species level.

Answer 8

• TCBS: Vibrio sp.
• O129 (150ug): Vibrio sp., Plesiomonas (R: Aeromonas sp.)
* only referring to G or S result

Question 9

Describe the pathogenesis, epidemiology and basic laboratory ID of V.cholerae.*

Answer 9

Pathogenesis: contaminated water supplies, eat seafood in contaminated water, ingest contaminated food
Lab ID: yellow on TCBS & S to O129 (10ug)

Question 10

What is the HACEK group? List the genera. What disease association do they have?

Answer 10

Haemophilus parainfluenzae
Aggregatibacter (actinobacillus)
Cardiobacterium hominis
Eikenella corrodens
Kingella sp.
* all associated w/ endocardial infections often isolated in blood culture

Question 11

What is the O129 compound?

Answer 11

is a pteridine derivative - used to differentiate Vibrio & Aeromonas sp.

Question 12

Helicobacter pylori lab features

Answer 12

• GNB curved
• Catalase & Oxidase pos
• Motile
• Urease pos (survive stomach acid)