Cat. no. C6920 CRITERION™ Selenite Cystine Broth 46gm
Cat. no. C6921 CRITERION™ Selenite Cystine Broth 500gm
Cat. no. C6922 CRITERION™ Selenite Cystine Broth 2kg
Cat. no. C6923 CRITERION™ Selenite Cystine Broth 10kg
Cat. no. C6924 CRITERION™ Selenite Cystine Broth 50kg


Hardy Diagnostics CRITERION™ Selenite Cystine Broth is a selective enrichment for isolation of Salmonella spp. from food, feces, dairy products and other sanitary materials.

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.


Selenite Cystine Broth is to be employed as an enrichment medium for detecting Salmonella in food materials, in particular egg products. The formulation corresponds to that recommended by the AOAC as a standard enrichment medium for Salmonella.(7) It is included among the standard methods media of the American Public Health Association and complies with the requirements of the United States Pharmacopoeia.

The original formula of Leifson has been modified with added cystine. (8) Leifson determined that Selenite Broth favored the growth of Salmonella while reducing the growth of fecal coliforms and enterococci. The growth and recovery of Salmonella in food samples can be hindered by non- Salmonella bacteria, substances indigenous to the food sample and in dried, processed food, the Salmonella may be present in low numbers and in an injured condition. Using protocols that involve preenrichment, selective enrichment and selective plating increase the likelihood of recovering Salmonella. In most standard method procedures Selenite Cystine Broth is recommended in the selective enrichment step. As a selective enrichment medium, Selenite Cystine Broth is formulated to allow the proliferation of Salmonella and while inhibiting the growth of competing non- Salmonella bacteria. The addition of cystine assists in lowering the toxicity of selenite to microorganisms. In addition, the extra organic sulphur provided may have a sparing effect in the critical sulphur components of the bacteria. Thus, reducing the effects of the selenite.

Selenite Cystine Broth contains tryptone as a source of carbon, nitrogen, vitamins and minerals. Lactose is the carbohydrate. Sodium acid selenite inhibits gram-positive bacteria and most enteric gram-negative bacteria except Salmonella. L-Cystine is a reducing agent.


Gram weight per liter: 23.0gm/L
Disodium Phosphate 10.0gm
L-Cystine 10.0gm
Pancreatic Digest of Casein 5.0gm
Lactose 4.0gm
Sodium Selenite 4.0gm

Final pH 7.0 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented to meet performance criteria.


Store the sealed bottle(s) containing 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 off-white. Notably, prolonged storage of this product may lead to changes in medium and possible deterioration in its selectivity.

Store the prepared culture media at 2-8ºC.



1. Suspend 23.0gm of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Heat to boiling and mix to dissolve completely.

3. Dispense into tubes.

4. Do not autoclave. Use immediately.

Alternatively, the broth may be filter sterilized and aseptically dispensed into sterile tubes.


For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. K69.


Selenite Cystine Broth is a selective enrichment for Salmonella. Other biochemical and/or serological tests must be performed for complete identification. See listed references.(1,3-5)

Do not incubate over 24 hours; the inhibitory effect diminishes after the first 6-12 hours of incubation. Incubation over 24 hours is not favorable to most Salmonella spp.

Refer to the keyword "Limitations", in the Hardy Diagnostics software program HUGO™, for more information regarding general limitations on culture media.


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


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Salmonella enterica
ATCC ® 14028
I 18-24hr 35°C Aerobic Good growth
Shigella flexneri
ATCC ® 12022
I 18-24hr 35°C Aerobic Partial to complete inhibition
Escherichia coli
ATCC ® 25922
I 18-24hr 35°C Aerobic Partial to complete inhibition

User Quality Control


CRITERION™ Selenite Cystine Broth powder should appear homogeneous, free-flowing, and off-white in color. The prepared media should appear clear to slightly opalescent, and very light amber in color. The prepared media may have a slight precipitate.


1. FDA. 1995. Bacteriological Analytical Manual, 8th ed. FDA.

2. Marshall, R.T., ed. 1992. Standard Methods for the Examination of Dairy Products, 16th ed. APHA, Washington, D.C.

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

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

5. U.S. Pharmacopeia, 22nd rev. 1990. U.S. Pharmacopeial Convention, Rockville, MD.

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

7. Association of Official Analytical Chemists. 1978. Bacteriological Analytic Manual, 5th ed. AOAC, Washington, D.C.

8. Leifson, E. 1936. New Selenite Selective Enrichment Medium for the Isolation of Typhoid and Paratyphoid (Salmonella) Bacilli. Am. J. Hyg.

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