Lab 1 Enterobacter Tests

TSI Agar Ingredients (7)

1. Glucose 1x

2. Sucrose 10x

3. Lactose 10x

4. Sodium thiosulfate

5. Peptones

6. Iron

7. PHENOL RED

Sodium Thiosulfate Function

Sodium thiosulfate complexes with iron

TSI Interpretations

1. A/A - Used sucrose or lactose and glucose

2. K/A - Uses peptones and glucose (Need O2 to do so)

3. K/ NC - Uses peptones only

Citrate Test Ingredients

1. Bromothymol blue

2. Sodium citrate

3. Ammonium diphosphate - Alkaline

Simmons citrate agar

Citrate Interpretation

• Positive test = Blue

Alkaline when pull ammonium off as carbon source

Nitrate Test Add Ins

1. Nitrate A - Sulfanilic acid

2. Nitrate B - Alpha-naphthylamine

3. Zinc

Sulfanilic acid

Converts p-diazonium benzene to sulfonic acid

Alpha-naphthylamine

Turns sulfonic acid into red pigment

Zinc

If nitrate present, it reduces it to nitrite

Nitrate Interpretation

1. Red after Nitrite A and B = Positive for Reduction

2. Red after Zinc = Negative

3. Colorless after Zinc = Positive for denitrification

Indole Test Looks for

1. Tryptophanase enzyme

2. Breaks down tryptophan into ammonia, pyruvic acid, and indole

3. Tryptic soy agar broth

Indole test add in

Kovac’s reagent

Indol interpretation

1. Red = positive

2. Yellow = negative

Urease Ingredients (Christensen’s agar)

1. Urea

2. Phenol red

3. Monopotassium phosphate (2g)

4. Agar (15 g)

Urease test function

1. Urease breaks down urea into ammonia and CO2

Urease test interpretation

1. All yellow = negative

2. Partial pink = 2+

3. All pink = 4+