Selenite Cystine Broth

Selenite Cystine Broth

EMD Cat. No. 1.07709.0500

500 g

For the enrichment of salmonellae from faeces, foodstuffs and other materials.

This culture medium complies with the recommendations of ISO Standard 6579 (1993), the American Public Health Association (1992), the United States Pharmacopeia XXIII (1995), the DIN Norm 10181 for the examination of milk and acc. to § 35 LMBG (German regulations) for food examination.

Mode of Action	Preparation
Experimental Procedure and Evaluation	Quality Control
Typical Composition (g/liter)	Literature

Mode of Action
Selenite inhibits the growth of coliform bacteria and enterococci in the first 6-12 hours of incubation, its inhibitory effect then gradually declines. Salmonella, Proteus and Pseudomonas are, however, only slightly inhibited.

Preparation
Storage of the dehydrated culture medium below 15 °C!
Suspend 23 g/liter at room temperature, if the medium does not dissolve readily, heat briefly (max. 60 °C); if the medium is to be stored, filter-sterilize; dispense into suitable containers.

Do not autoclave.
pH: 7.0 ± 0.2 at 25 °C.
The prepared broth is clear and yellowish.
After a longer storage period of the dehydrated medium, the color of the prepared broth might change to redish/red. The microbiological performance however is not affected.

Experimental Procedure
Add solid material to the normal-strength broth. Mix liquid samples with double-strength broth in the ratio 1:1.
Incubation: up to 24 hours at 35-37 °C - according to BÄNFFER (1971) and other authors, 43 °C is better.

After 6-12 hours and, if necessary, after 18-24 hours inoculate material from the resulting culture onto selective culture media.

Quality control

Test strains	Inoculum	Growth after
		24 hours
Escherichia coli ATCC 25922	approx. 99 %	10 %
Salmonella typhimurium ATCC 14028	approx. 1 %	90 %

Typical Composition (g/liter)
Peptone from casein 5.0; L(-)cystine 0.01; lactose 4.0; phosphate buffer 10.0; sodium hydrogen selenite 4.0.

Literature

American Public Health Association: Compendium of methods for the microbiological examination of foods. - 3rd ec., 1992.
BÄNFFER, J.R.: Comparison of the isolation of Salmonellae from human faeces by enrichment at 37 °C and at 43 °C. - Zbl. Bakt. I. Orig., 217; 35-40 (1971).
Bundesgesundheitsamt: Amtliche Sammlung von Untersuchungsverfahren nach § 35 LMBG. - Beuth Verlag Berlin, Köln.
DIN Deutsches Institut für Normung e.V.: Mikrobiologische Milchuntersuchung. Nachweis von Salmonellen. Referenzverfahren. - DIN 10181.
United States Pharmacopeia XXIII, Chapter "Microbial Limit Tests" (1995).