Cat. no. L15 Acetate Differential Slant, 16x100mm Tube, Slant 20 or 100 tubes/box


Hardy Diagnostics Acetate Differential Slant is used to differentiate Escherichia coli from members of the genus Shigella.


The Acetate Differential Slant is formulated with the base formula of Simmons Citrate Agar, but sodium citrate is replaced with sodium acetate. Differentiation is based on the organisms ability to utilize acetate. Approximately 84% of E. coli species utilize acetate, whereas the majority of Shigella species are incapable of acetate utilization.(5) 7.7% Shigella flexneri 4a, mannitol +, and 86% Shigella flexneri 4a, mannitol -, are capable of utilizing acetate.(6)


Ingredients per liter of deionized water:*

Sodium Chloride 5.0gm
Sodium Acetate 2.0gm
Monoammonium Phosphate 1.0gm
Dipotassium Phosphate 1.0gm
Magnesium Sulfate 0.1gm
Bromothymol Blue 0.08gm
Agar 20.0gm

Final pH 6.7 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.


Storage: Upon receipt store at 2-30ºC. away from direct light. Media should not be used if there are any signs of deterioration (shrinking, cracking, or discoloration), hemolysis, contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat and freezing.



Specimen Collection: Consult listed references for information on specimen collection.(1-4) Infectious material should be submitted directly to the laboratory without delay and protected from excessive heat and cold. If there is to be a delay in processing, the specimen should be inoculated onto an appropriate transport media and refrigerated until inoculation.

The proper performance of the Acetate Differential Slant depends upon the inoculation from a pure culture. Using an 18-24 hour old culture from a non-inhibitory culture plate, prepare a saline suspension. Inoculate the slant with a straight wire from the saline suspension. The butt of the medium may be stabbed, if desired.


A positive result is indicated by the presence of growth and the media around the colony turning blue.


Specimen Collection: This product is not intended for primary isolation of patient specimens. This product is used in conjunction with other biochemical tests to identify cultures of isolated organism.

Certain strains of Shigella flexneri are capable of utilizing acetate. 7.7% of Shigella flexneri 4a, mannitol +, and 86% of Shigella flexneri 4a, mannitol -, are acetate-positive.


Standard microbiological supplies and equipment such as loops, saline, other culture media, swabs, applicator sticks, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC® 25922
E 24-96hr 35°C Aerobic Growth; media turns blue around colonies
Shigella flexneri
ATCC® 12022
E 24-96hr 35°C Aerobic Inhibited

User Quality Control


Acetate Differential Slant should appear slightly opalescent, and green in color.

E. coli on Acetate Differential Slant

Escherichia coli (ATCC® 25922) colonies growing on Acetate Differential Slant (Cat. no. L15). Incubated aerobically for 24 hours at 35ºC.

S. flexneri inhibted on Acetate Differential Slant

Shigella flexneri (ATCC® 12022) inhibited on Acetate Differential Slant (Cat. no. L15). Incubated aerobically for 24 hours at 35ºC.


1. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

2. Baron, E.J. and S.M. Finegold. 1990. Bailey and Scott's Diagnostic Microbiology, 8th ed. C.V. Mosby Company, St. Louis, MO.

3. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

4. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I & II. American Society for Microbiology, Washington, D.C.

5. Pub. Hlth. Lab.; 20:137. 1962.

6. Ewing, W.H., et al. 1971. Biochemical Reactions of Shigella, Public Health Service, Centers for Disease Control, Atlanta, GA.