Cat. no. C6360 CRITERION™, Modified Listeria Enrichment Broth 72.2gm
Cat. no. C6361 CRITERION™, Modified Listeria Enrichment Broth 500gm
Cat. no. C6362 CRITERION™, Modified Listeria Enrichment Broth 2kg
Cat. no. C6363 CRITERION™, Modified Listeria Enrichment Broth 10kg
Cat. no. C6364 CRITERION™, Modified Listeria Enrichment Broth 50kg


Hardy Diagnostics CRITERION™ Modified Listeria Broth is used for selectively enriching Listeria monocytogenes from raw and pasteurized milk according to the International Dairy Federation (IDF) and the U.S. FDA Bacteriological Analytical Manual (BAM).(5,6)

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.


First described by Murray, Webb, and Swann, Listeria monocytogenes is a widespread problem in public health and the food industries.(7) This organism can cause human illness and death, particularly in immunocompromised individuals and pregnant women. The first reported food-borne outbreak of listeriosis was in 1985.(5) Since then, microbiological and epidemiological evidence from both sporadic and epidemic cases of listeriosis has shown that the principal route of transmission is via the consumption of foodstuffs contaminated with Listeria monocytogenes.(9)

Implicated vehicles of transmission include turkey frankfurters, coleslaw, pasteurized milk, Mexican-style and other soft cheeses, pate and pickled pork tongue.(5) The organism has been isolated from commercial dairy and other food processing plants.(6) It is ubiquitous in nature, being present in a wide range of unprocessed foods and in soil, sewage, silage and river water.

Listeria spp. grow over a pH range of 5.0-9.6 and survive in food products with pH levels outside these parameters.(11)

Listeria Enrichment Broth is based on the formula developed by Lovett, et al. in which Tryptic Soy Broth was supplemented with yeast extract for optimum growth of Listeria spp.(12) Modified Listeria Enrichment Broth is an adjusted version of Listeria Enrichment Broth in which the acriflavine content has been reduced from 15.0mg to 10.0mg per liter. This modification reflects the formula specified by the FDA and the International Dairy Federation for isolation of L. monocytogenes from milk and milk products.(5,6)

Modified Listeria Enrichment Broth contains pancreatic digest of casein, papaic digest of soybean meal, and yeast extract as nitrogen and vitamin sources. Dextrose provides an energy source. Sodium chloride maintains the osmotic balance of the medium. Dipotassium phosphate is a buffering agent. Nalidixic acid is incorporated to inhibit growth of gram-negative organisms, while acriflavine is added to suppress growth of gram-positive bacteria. The antifungal cycloheximide may be added aseptically in order to comply with BAM and the IDF.

Identification of Listeria spp. is based on successful isolation of the organism, biochemical characterization and serological confirmation.


Gram weight per liter: 36.1gm/L
Pancreatic Digest of Casein 17.0gm
Papaic Digest of Soybean Meal 3.0gm
Dextrose 2.5gm
Sodium Chloride 5.0gm
Dipotassium Phosphate 2.5gm
Yeast Extract 6.0gm
Acriflavine 0.01gm
Nalidixic Acid 0.04gm

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. Protect dehydrated culture media from moisture and light. The dehydrated culture medium is very hygroscopic. The dehydrated media should be discarded if it is not free-flowing or if the color has changed from its original light beige.

Store prepared medium at 2-8ºC.



1. Suspend 36.1gm 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.

4. Aseptically add antifungal to cooled media as desired. FDA, BAM, and IDF recommendation: cycloheximide (50.0mg/L). Alternate suggestion: amphotericin B (2.0mg/L).


For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. K57.


Since the nutritional requirements of organisms vary, some strains of Listeria spp. may be encountered that fail to grow or grow poorly on this medium.

Modified Listeria Enrichment Broth is a partially selective medium. Growth of some contaminating strains will be markedly but not totally inhibited.


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


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Listeria monocytogenes
ATCC ® 7644
A 24-48hr 35°C Aerobic Growth
Staphylococcus aureus
ATCC ® 25923
B 24-48hr 35°C Aerobic Partial to complete inhibition
Escherichia coli
ATCC ® 25922
B 24-48hr 35°C Aerobic Partial to complete inhibition

User Quality Control


CRITERION™ Modified Listeria Broth powder should appear homogeneous, free-flowing, and light beige in color. The prepared media should appear clear, with a slight opalescence, and light amber in color.


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

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

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

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

5. U.S. Food and Drug Administration. Bacteriological Analytical Manual. AOAC, Arlington, VA.

6. International Dairy Federation. 1990. Milk and milk products - detection of Listeria monocytogenes. IDF Provisional International Standard No. 143. International Dairy Federation, Brussels.

7. Murray, E.G, et al. 1926. A disease of rabbits characterized by large mononuclear leucocytosis caused by a hitherto undescribed bacillus Listeria monocytogenes. J. Path. Bact.; 19:407-439.

8. Monk, J.D, et al. Irradiation inactivation of Listeria monocytogenes and Staphylococcus aureus in law and high-fat frozen and refrigerated ground beef. J. Food Prot.; 57:769-772.

9. Wehr, H.M. 1987. Listeria monocytogenes - a current dilemma Special Report. J. Assoc. Anal. Chem.; 80:769-7762.

10. Grau, F.H., et al. 1995. Occurrence, numbers, and growth of Listeria monocytogenes on some vacuum-packaged processed meats. J. Food Prot.; 55:4-4.

11. Kramer, P.A., et al. 1969. Media selective for Listeria monocytogenes. J. Appl. Bacteriology; 32:381-394.

12. Lovett, J.D., et al. 1987. Listeria monocytogenes. J. Food Prot.; 50:188-192.

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