CRITERION™ EMB (EOSIN METHYLENE BLUE) AGAR, HHT (HOLT-HARRIS AND TEAGUE)

Cat. no. C7330 CRITERION™ EMB Agar, HHT 72gm
Cat. no. C7331 CRITERION™ EMB Agar, HHT 500gm
Cat. no. C7332 CRITERION™ EMB Agar, HHT 2kg
Cat. no. C7333 CRITERION™ EMB Agar, HHT 10kg
Cat. no. C7334 CRITERION™ EMB Agar, HHT 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ EMB Agar, HHT is recommended for the isolation and identification of gram-negative enteric bacteria.

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.(1) 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.(2-6) Gram-positive bacteria are inhibited by eosin Y.

FORMULA

Gram weight per liter: 36.0gm/L
Gelatin Peptone 10.0gm
Lactose 5.0gm
Sucrose 5.0gm
Dipotassium Phosphate 2.0gm
Eosin Y 0.4gm
Methylene Blue 65.0mg
Agar 13.5gm

Final pH 7.2 +/- 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 pinkish-purple.

Store the prepared culture media at 2-8ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 36.0gm 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.

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. G263.

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.

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; colonies blue-black with dark centers and green metallic sheen
Salmonella enterica
ATCC ® 14028
A 24hr 35°C Aerobic Growth; colonies colorless to amber
Enterococcus faecalis
ATCC ® 29212
B 24hr 35°C Aerobic Partial to complete inhibition; pinpoint colonies at 24 hours

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ EMB Agar, HHT powder should appear homogeneous, free-flowing, and pinkish-purple in color. The prepared media should appear clear, usually with a fine precipitate evenly dispersed throughout, and purple with green-orange tinge in color.

REFERENCES

1. J. Infectious Diseases; 18:596, 1916.

2. 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.

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

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

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

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

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


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

052316gr