Microbes in Water Lab

What is the purpose of Mannitol Salt Agar (MSA)?

To observe mannitol fermentation for identifying skin bacteria.

What should you observe after the MSA experiment?

Trehalose broth results.

What should be used to identify skin microbiota?

The identification key.

What characteristic do all enterics share?

They are gram-negative, oxidase-negative bacilli.

What metabolic characteristic do all enterics have?

They produce acid from glucose fermentation.

Which two media are primarily used to identify enterics?

MacConkey agar and TSI.

What is the first division in the enteric identification key?

Lactose fermenters vs. non-lactose fermenters.

What characteristic identifies Citrobacter among lactose fermenters?

H₂S production.

What characteristic identifies Escherichia among lactose fermenters?

Indole production.

What characteristic identifies Enterobacter among lactose fermenters?

Motility.

What characteristic identifies Klebsiella among lactose fermenters?

Nonmotility.

Which lactose fermenter is H₂S positive?

Citrobacter.

Which lactose fermenter is indole positive?

Escherichia.

Which lactose fermenter is motile?

Enterobacter.

Which lactose fermenter is nonmotile?

Klebsiella.

Among non-lactose fermenters, what is evaluated first?

Gas production from glucose fermentation.

Which organism is identified by H₂S production and urease?

Proteus.

Which organism is H₂S positive, urease negative, and ferments mannitol?

Salmonella.

Which organism is H₂S positive, urease negative, and does not ferment mannitol?

Edwardsiella.

Which organism produces pigment at 25°C?

Serratia.

Which organism lacks pigment at 25°C?

Shigella.

Which organism is ornithine decarboxylase positive?

Morganella.

Which organism is ornithine decarboxylase negative?

Providencia.

What should be observed during Ex. 5-21?

TSI slant.

How should TSI results be interpreted?

Using Table 5-24 on page 207.

Where are the Rapid ID instructions found?

Pages 451–453.

Where is the Rapid ID interpretation table?

Page 454.

What should be determined on the blood agar plate?

Type of hemolysis.

What should be observed on MacConkey agar in the urogenital tract lab?

Whether coliforms are present.

What should the Uricheck paddle be compared with?

The colored chart.

What additional step is required for the Uricheck paddle?

Use side 2 of the Uricheck handout (Quality Control #3) to identify organisms.

What are coliforms used as?

Indicator organisms.

What is the first step of the Multiple-Tube Test?

Presumptive test.

What medium is used in the presumptive test?

Lactose broth.

What value is determined in the presumptive test?

MPN per 100 mL.

What does MPN stand for?

Most Probable Number.

What is the second step of the Multiple-Tube Test?

Confirmed test.

What medium is used for the confirmed test?

MUG agar.

What enzyme is detected by MUG agar?

β-glucuronidase.

How many single-strength lactose fermentation tubes are used?

6.

How many 1.5-strength lactose fermentation tubes are used?

3.

How are the six single-strength tubes labeled?

Three labeled 0.1 and three labeled 1.0.

How are the three 1.5-strength tubes labeled?

All labeled 10.

How much water is added to the 0.1 tubes?

0.1 mL.

How much water is added to the 1.0 tubes?

1.0 mL.

How much water is added to the 10 tubes?

10 mL.

At what temperature are the lactose fermentation tubes incubated?

37°C.

Which organism appears as yellow colonies with metallic green or purple colonies on EMB?

Escherichia coli.

Which organism produces translucent colonies with blue CLED medium?

Proteus vulgaris.

Which organism produces translucent colonies with blue CLED medium and colorless EMB colonies?

Salmonella typhimurium.

Which organism produces yellow colonies on CLED and pinpoint colonies on EMB?

Enterococcus faecalis.

Which organism produces yellow colonies on CLED only?

Staphylococcus aureus.

Which enteric test distinguishes lactose fermenters from non-lactose fermenters?

MacConkey agar.

Which test helps identify H₂S-producing enterics?

TSI.

What are the three inoculation volumes used in the Multiple-Tube Test?

0.1 mL, 1.0 mL, and 10 mL.

What is the purpose of the confirmed test?

To detect β-glucuronidase-positive coliforms using MUG agar.

Which organisms are identified using the skin microbiota key?

Gram-positive cocci from the skin.

What observation is required before using the skin microbiota key?

Trehalose broth results.

What observation is required before interpreting the Uricheck paddle?

Compare growth to the colored chart.

What observation is required before identifying organisms on the Uricheck paddle?

Use Quality Control #3 on side 2 of the handout.

Which experiment uses TSI slants?

Bacteria of the GI Tract (Ex. 5-21).

Which experiment uses blood agar, MacConkey agar, and the Uricheck paddle?

Bacteria of the Urogenital Tract (Ex. 6-2).

Which experiment uses lactose broth and MUG agar?

Microbes in Water (Ex. 8-13).

What is the incubation temperature for the Multiple-Tube Test?

37°C.