Cat. no. C7590 CRITERION™ Esculin Mannitol Agar 108gm
Cat. no. C7591 CRITERION™ Esculin Mannitol Agar 500gm
Cat. no. C7592 CRITERION™ Esculin Mannitol Agar 2kg
Cat. no. C7593 CRITERION™ Esculin Mannitol Agar 10kg
Cat. no. C7594 CRITERION™ Esculin Mannitol Agar 50kg


Hardy Diagnostics CRITERION™ Esculin Mannitol Agar is a dual purpose medium. It is recommended for use as a differential medium for the presumptive identification of enterococci, and a selective and differential medium for the isolation of Staphylococcus aureus. This media is particularly useful for the testing of dairy foods.

This dehydrated culture medium is a raw material intended to be used in the making of prepared media products, which will require further processing, additional ingredients, or supplements.


Because enterococci have a higher survival rate than coliforms in adverse environments, such as salted butter and the low pH of yogurt, they are generally better index organisms for the sanitary conditions of dairy products Staphylococcus aureus can be found in raw milk, dry milk, cheese and ice cream. CRITERION™ Esculin Mannitol Agar is helpful in recovering these pathogens.(7)

This medium contains esculin and ferric citrate. When esculin is hydrolyzed by group D streptococci it becomes esculetin. Esculetin reacts with the ferric ions from the ferric citrate and turns the medium from its original amber color to a dark brown or black. This blackening of the agar is a presumptive identification for group D enterococci.(3)

Staphylococcus aureus, which grows well on this agar, ferments mannitol. Non-pathogenic staphylococci usually show less luxuriant growth on this medium and do not ferment mannitol.  Phenol red acts as a pH indicator. When mannitol is fermented, acid is produced which causes a color change in the agar from red to yellow. Those staphylococci that do not ferment mannitol show a purple or red zone around the colonies.(5) The beef extract and peptones supply the essential carbon, nitrogen and sulfur.


Gram weight per liter: 54.0gm/L
Pancreatic Digest of Casein 10.0gm
Mannitol 10.0gm
Yeast Extract 5.0gm
Peptic Digest of Animal Tissue 5.0gm
Sodium Chloride 5.0gm
Brain Heart Infusion 3.0gm
Corn Starch 1.0gm
Esculin 1.0gm
Ferric Ammonium Citrate 0.5gm
Phenol Red 25.0mg
Nalidixic Acid 15.0mg
Colistin Sulfate 10.0mg
Agar 13.5gm

Final pH 7.3 +/- 0.2 at 25ºC.

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


Store the sealed bottle(s) containing dehydrated culture medium at 2-30ºC. Dehydrated culture medium is very hygroscopic. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated culture media should be discarded if it is not free-flowing or if the color has changed from its original pinkish-beige.

Store the prepared culture media at 2-8ºC.



1. Suspend 54.0gm of the dehydrated culture media in 1 liter of distilled or deionized water. Stir to mix thoroughly.

2. Heat to boiling to dissolve completely.

3. Sterilize in the autoclave at 121ºC. for 15 minutes.

4. Cool to 45-50ºC.


For information on procedures and interpretation of results, consult listed references.



Standard microbiological supplies and equipment such as autoclaves, incinerators, and incubators, etc., are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Staphylococcus aureus
ATCC ® 25923
A 18-48 hr 35°C Aerobic Growth; media turns yellow at 24-48 hours
Enterococcus faecalis
ATCC ® 29212
A 18-48 hr 35°C Aerobic Growth; blackening of media around colonies
Proteus mirabilis
ATCC ® 12453
A 18-48 hr 35°C Aerobic Partial to complete inhibition
Pseudomonas aeruginosa
ATCC ® 27853
A 18-48 hr 35°C Aerobic Partial to complete inhibition

User Quality Control


CRITERION™ Esculin Mannitol Agar powder should appear homogeneous, free-flowing, and pinkish-beige in color. The prepared media should appear clear, and red in color.


1. 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.

2. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

3. MacFaddin, J.F. Biochemical Tests for Identification of Medical Bacteria,, Lipincott Williams & Wilkins, Philadelphia, PA.

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

5. MacFaddin, J.F. 1985. Media for Isolation, Cultivation, Identification, Maintenance of Bacteria, Vol. I. Williams & Wilkins, Baltimore, MD.

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

7. Marshall, R.T. 1993. Standard Methods for the Examination of Dairy Products, 13th ed. APHA, Washington, D.C.

8. Vanderzant, C. and D.F. Splittstoesser, (ed.). 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. APHA, Washington, D.C.

9. Koneman, E.W., et al. Color Atlas and Textbook of Diagnostic Microbiology, J.B. Lippincott Company, Philadelphia, PA.

ATCC is a registered trademark of the American Type Culture Collection.