Acetate Utilization Test
DESCRIPTION
The basal mineral medium is alcalinized by bacteria which utilize acetate as sole carbon source. Test is used for nonfermentative

Gram-negative microorganisms. Also, inactive
Escherichia coli biotype can be differentiated from Shigella.
MEDIUM PREPARATION

Sodium acetate medium (2%):
NaCl .......................................................................................... 5.0 g
MgSO
2 * 7H2O .......................................................................... 0.2 g
NH
4H2PO4 ................................................................................. 1.0 g
K
2HPO4 ..................................................................................... 1.0 g
Sodium acetate (CH
3COONa) ............................................. 2.0 g
Agar ........................................................................................ 20.0 g
Bromtymol blue 0.2% solution ........................................... 40 ml
Distilled water ..................................................................... 960 ml
Dissolve ingredients in water and adjust to pH 6.8 (use 1N NaOH solution).
Filter if necessary. Add agar and heat for melting it. Distribute in tubes,
autoclave 15 min at 121 °C, create a slant when cooling the tubes.

PROCEDURE
Harvest a well isolated colony and inoculate an acetate medium tube by  zigzag streaking on the surface of the slant. Incubate at 37
°C, 18-24 hours.

READING
Reaction is positive if medium changes color to blue and culture growth is visible on surface.
Reaction is negative if medium remains green.
REFERENCES:
1. Dumitru Buiuc, Mihai Zamfirescu: Teste de identificare a microorganismelor, in Dumitru Buiuc, Marian Negut, Tratat de
microbiologie clinica, 3-rd ed., 2009, 1102-1103.
2. Costin I.D.: Utilization of sodium acetate by Shigella and Escherichia. J.Gen. Micrbiol., 41; 23-27, 1965.
(c) Costin Stoica
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