Acetate Utilization

Question 1

What the purpose of acetate utilization?

Answer 1

Differentiate organisms based on the ability of an organism to utilize acetate as a sole source of carbon.Generally used to differentiate Shigella sp. from Escherichia coli.

Question 2

Principle of acetate is:

Answer 2

This test is used to differentiate an organism capable of using acetate as the sole source of carbon. Organisms capable of using sodium acetate grow on the medium, resulting in an alkaline pH, turning the indicator from green to blue.

Question 3

Acetate media made of :

Answer 3

NaC2H3O2 (2 g)
MgSO4 (0.1 g)
NaCl (5 g)
NH4H2PO4 (1 g)
agar (20 g)
bromthymol blue indicator (0.8 g)
per 1000 mL
pH 6.7.

Question 4

Method of acetate :

Answer 4

1-With a straight inoculating needle, inoculate acetate slant lightly from an 18- to 24-hour culture. Do not inoculate from a broth culture but rather from a plate.

2-Incubate at 35°-37°C for up to 7 days.

Question 5

Expected results for acetate utilization:

Answer 5

Positive: Medium becomes alkalinized (blue) as a result of the growth and use of acetate.
Negative: No growth or growth with no indicator change to blue.

Question 6

Limitations of acetate:

Answer 6

Some strains of E. coli may use acetate at a very slow rate or not at all, resulting in a false negative reaction in the identification process.

Question 7

Quality control for acetate:

Answer 7

Positive: E. Coli- growth: blue
Negative: shigella sonni- small amount of growth:green