CRITERION™ EMB (EOSIN METHYLENE BLUE) AGAR, LEVINE

Cat. no. C5700 CRITERION™ EMB Agar, Levine 75gm
Cat. no. C5701 CRITERION™ EMB Agar, Levine 500gm
Cat. no. C5702 CRITERION™ EMB Agar, Levine 2kg
Cat. no. C5703 CRITERION™ EMB Agar, Levine 10kg
Cat. no. C5704 CRITERION™ EMB Agar, Levine 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ EMB Agar, Levine is recommended for use as a selective and differential medium for the isolation of gram-negative bacilli (including coliform organisms and enteric pathogens).

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.

SUMMARY

Eosin Methylene Blue (EMB) Agar was originally developed by Holt-Harris and Teague. Eosin dye was employed to inhibit the growth of gram-positive bacteria. Methylene blue was added as an indicator. Lactose and sucrose served as the nutrients. The production of acid, upon lactose- or sucrose-fermentation, resulted in the two dyes interacting to produce brown to blue-black colonies. This formulation gives sharp and distinct differentiation between colonies of lactose- and non-lactose-fermenting organisms. However, it does not discriminate between which carbohydrate (lactose or sucrose) is being fermented. Yersinia enterocolitica, which ferments sucrose but not lactose, will produce the same blue-black colony as lactose-fermenters.(1-6)

Levine modified the formula by omitting sucrose and doubling the level of lactose. The resultant medium gives excellent differentiation of Escherichia coli from Enterobacter aerogenes. This formulation, by eliminating sucrose, provides reactions that are more in parallel with MacConkey Agar.

EMB Agar, Levine has become the predominant enteric plating medium that utilizes dyes as selective agents. The American Public Health Association recommends its use in the microbiological examination of potable water, waste water, dairy products and foods.(8,9) The USP recommends its use in the performance of Microbial Limit Tests.(10)

FORMULA

Gram weight per liter: 37.5gm/L
Pancreatic Digest of Gelatin 10.0gm
Lactose 10.0gm
Dipotassium Phosphate 2.0gm
Eosin Y 0.4gm
Methylene Blue 65.0mg
Agar 15.0gm

Final pH 7.1 +/- 0.2 at 25ºC.

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

STORAGE AND SHELF LIFE

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 reddish-purple.

Store the prepared culture medium at 2-8ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 37.5gm of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Heat to boiling and mix to dissolve completely.

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

4. Dispense as desired into sterile containers.

PROCEDURE AND INTERPRETATION OF RESULTS

For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. G25.

LIMITATIONS

Some gram-positive bacteria, such as enterococci, staphylococci and yeasts will grow on this medium and usually form pinpoint colonies.

Non-pathogenic, non-lactose-fermenting organisms will also grow on this medium.

Additional biochemical tests must be performed in order to distinguish these organisms from the pathogenic bacterial strains.

Serial inoculation may be required to assure adequate isolation of mixed flora samples.

MATERIALS REQUIRED BUT NOT PROVIDED

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

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC ® 25922
A 24hr 35°C Aerobic Growth; blue-black centered colonies with green metallic sheen
Salmonella enterica
ATCC ® 14028
A 24hr 35°C Aerobic Growth; colorless to amber colonies
Enterococcus faecalis
ATCC ® 29212
B 24hr 35°C Aerobic Pinpoint colonies at 24 hours

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ EMB Agar, Levine powder should appear homogeneous, free-flowing, and reddish-purple in color. The prepared media should clear, and reddish-purple with slight orange tinge in color.

REFERENCES

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

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

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

5. MacConkey, A.T. 1905. Lactose-fermenting bacteria in faeces. J. Hyg.; 5:333-379.

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

7. Quality Assurance for Commercially Prepared Microbiological Culture Media, M22. Clinical and Laboratory Standards Institute (CLSI - formerly NCCLS), Wayne, PA.

8. Standard Methods for the Examination of Dairy Products, 9th ed. 1948.

9. Greenberg, A.E., et al., (ed.). 1992. Standard Methods for the Examination of Water and Wastewater, 18th ed. APHA, Washington, D.C.

10. The United States Pharmacopeia, 22nd rev. 1990. United States Pharmacopeial Convention, Rockville, MD.


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

052316gr