Micro lab gram negative plates

Is citrate agar Gram + or Gram -?

Either

What does a visual description of growth, plate turns blue with citrate agar mean?

Organism has the ability to use citrate as a carbon source

What does a visual description of no growth, plate remains green
with citrate agar mean?

Organism does not have the ability to use citrate as a carbon source

Is motility Gram + or Gram -?

Either

Is MAC Gram + or Gram -?

Gram -

Is MAC selective or differential?

Both

What are the selecting agents in MAC?

Bile salts and crystal violet

What are the differentiating agents in MAC?

Lactose and neutral red

What does a visual description of positive growth with pink appearing colonies mean in MAC?

Gram-negative organism with the ability to ferment lactose.

What does a visual description of positive growth with tan appearing colonies mean in MAC?

Gram-negative organism without the ability to ferment lactose.

What does a visual description of no growth mean in MAC?

It is a gram positive organism

Is TSI gram + or gram -?

Either

Is TSI selective or differential?

Differential

What are the differentiating agents in TSI?

Glucose, lactose, sucrose, phenol red, sodium thiosulfate, ferric citrate

What does a visual description of (Slant/Butt) yellow/yellow mean in TSI and the symbol?

Glucose and lactose and/or sucrose fermentation

A/A

What does a visual description of (Slant/Butt) red/yellow mean in TSI and the symbol?

Glucose fermentation only

K/A

What does a visual description of (Slant/Butt) red/red mean in TSI and the symbol?

No fermentation, growth throughout

K/K

What does a visual description of (Slant/Butt) red/no change mean in TSI and the symbol?

No fermentation, aerobic growth only

K/NC

What does a visual description of (Slant/Butt) no change/no change mean in TSI and the symbol?

No growth

NC/NC

What does a visual description of (Slant/Butt) black precipitate in agar mean in TSI and the symbol?

Hydrogen sulfide gas production

+H₂S

What does a visual description of (Slant/Butt) cracks or lifts in the agar mean in TSI and the symbol?

Gas produced by fermentation

+G

Is HEK Gram + or Gram -?

Gram -

Is HEK selective or differential?

Both

What are the selecting agents in HEK?

Bile salts

What are the differential agents in HEK?

Lactose, sucrose, salicin, bromothymol blue, acid fushsin, ferric ammonium citrate 

What does a visual description of positive growth, no color change (growth the color of the plate) mean in HEK?

Organism is gram-negative, does not ferment the sugars and does not produce hydrogen sulfide gas

What does a visual description of positive growth, orange colonies mean in HEK?

Organism is gram-negative, does ferment the sugars and does not produce hydrogen sulfide gas

What does a visual description of positive growth, growth the color of the plate, black edges mean in HEK?

Organism is gram-negative, does not ferment the sugars and does produce hydrogen sulfide gas

What does a visual description of positive growth, orange colonies, black edges mean in HEK?

Organism is gram-negative, does ferment the sugars and does produce hydrogen sulfide gas

What does a visual description of no growth mean in HEK?

Gram + organism

Is EMB gram + or gram -?

Gram -

Is EMB selective or differential?

Both

What are the selecting agents in EMB?

Eosin Y and Methylene blue

What are the differential agents in EMB?

Lactose and sucrose

What does a visual description of positive growth with colonies appearing the color of the plate (no color change) mean in EMB?

Gram-negative organism unable to ferment lactose or sucrose

What does a visual description of positive growth with colonies appearing pink mean in EMB?

Gram-negative organism considered a slow fermenter of lactose and/or sucrose

What does a visual description of positive growth with colonies appearing black/metallic green mean in EMB?

Gram-negative organism considered a vigorous fermenter of lactose and/or sucrose

What does a visual description of no growth mean in EMB?

Gram positive organism

What does the oxidase test look for?

Looks for the presence of cytochrome oxidase – protein used as part of the electron transport chain of some organisms

What does the oxidase test use?

Uses Oxidase Reagent – contains a chromogenic reducing agent

What is a positive oxidase test?

Positive result changes color, indicates presence of cytochrome oxidase