Bacterial Identification: Gram Negative Bacteria Tests - Lab Practical 5 Checklist

Which test is always performed first when identifying an unknown bacterium?

• Gram stain

Using a dichotomous key and the result from a test to determine the next best test to perform

• Oxidase test

Be able to determine an unknown bacterial species using the last test result and the dichotomous key

• Motility test if positive: the bacterium is Enterobacter aerogenes

Be able to identify a positive result

• Dark blue to purple

Be able to identify a negative result

• Colorless/ light tan

Name the reagent for an oxidase test

• Oxidase test reagent

In a Glucose Fermentation Test, be able to identify a positive result for both fermentation and gas

• Yellow

In a Glucose Fermentation Test, be able to identify a negative result for both fermentation and gas

• Red

What media is used in a Glucose Fermentation Test?

• Glucose broth

What indicator is used in a Glucose Fermentation Test?

• Phenol red

Name the small inverted test tube in the larger test tube in the Glucose Fermentation Test

• Durham tube

Be able to identify a positive result in a Nitrate Reduction Test

• Red

Be able to identify a negative result in a Nitrate Reduction Test

• White

Name the media used in a Nitrate Reduction Test

• Nitrate broth

Name the reagent in a Nitrate Reduction Test

• Nitrate test reagent

What type of media is MacConkey’s (MAC) agar for lactose fermentation?

• Selective and differential media

What is selective property in MAC agar for lactose fermentation?

• Bile salts

What bacteria grows on the media in MAC agar for lactose fermentation?

• Gram negative

What is differential property from MAC agar for lactose fermentation?

• Ferment lactose

Know what it means if the colonies are white in a MAC agar for lactose fermentation

• Doesn’t ferment lactose (noncoliform)

Know what it means if the colonies are pink in a MAC agar for lactose fermentation

• Ferments lactose (coliform)

Be able to identify a positive result in a Methyl Red Test

• Red

Be able to identify a negative result in a Methyl Red Test

• Yellow

Know the product of glucose fermentation being tested for in a Methyl Red Test

• Mixed acids

What media is being used in a Methyl Red Test?

• MRVP broth

What reagent in being used in a Methyl Red Test?

• Methyl Red

Be able to identify a positive result in a Hydrogen Sulfide Test

• Black in agar

Be able to identify a negative result in a Hydrogen Sulfide Test

• No black

Name the media in a Hydrogen Sulfide Test

• Kilger’s iron agar

Be able to identify a positive result in a Indole Test

• Pink oily layer

Be able to identify a negative result in a Indole Test

• Yellow oily layer

Name the media in an Indole Test

• Tryptone broth

Name the reagent in an Indole Test

• Kovac’s reagent

Be able to identify a positive result in a Motility Stab Tube Test

• Wide, fuzzy growth

Be able to identify a negative result in a Motility Stab Tube Test

• Straight growth

Name the media used in a Motility Stab Tube Test

• TTC agar

What is the physical property of the media TTC agar?

• semisolid

Be able to identify a positive result in a Urease Test

• Bright pink

Be able to identify a negative result in a Urease Test

• Orange/yellow

Name the media in a Urease Test

• Urea broth

Name the indicator in a Urease Test

• Phenol

Be able to identify a positive result in a Citrate Utilization Test

• Blue at top

Be able to identify a negative result in a Citrate Utilization Test

• All green

Name the media in a Citrate Utilization Test

• Simmon’s citrate agar

Name the indicator in a Citrate Utilization Test

• Bromothymol blue