Cat. no. K45 SF Broth, 16x125mm Tube, 5ml 20 or 100 tubes/box


Hardy Diagnostics SF Broth is recommended for the cultivation and differentiation of group D enterococci from group D non-enterococci.


In general Enterococcus inhabit the intestinal tract of both warm and cold-blooded animals. Enterococcus faecalis and E. faecium are heat resistant and are able to survive milk pasteurization. E. faecium is especially heat tolerant. Other enterococci, especially those that are highly resistant to antibiotics, can cause serious illness to humans. Because enterococci have the ability to survive and grow in food processing plants they serve as a good index of sanitation. (8)

SF Broth is prepared according to the formulation developed by Hajna and Perry. (3) The medium contains 0.05% sodium azide, casein peptone, dextrose and bromcresol purple. Sodium azide acts as the selective agent by inhibiting the cytochrome oxidase enzyme in the electron transport chain. Casein peptone and dextrose supply necessary growth nutrients. Bromcresol purple serves as the color indicator.

Specimens containing group D enterococci result in the production of acid from dextrose fermentation. Acid production is noted by a color change in the medium from purple to yellow by use of bromcresol as the pH indicator. Appearance of the yellow color change is indicative of the presence of group D enterococci.


Ingredients per liter of deionized water:*

Peptic Digest of Casein 20.0gm
Dextrose 5.0gm
Sodium Chloride 5.0gm
Dipotassium Phosphate 4.0gm
Monopotassium Phosphate 1.5gm
Sodium Azide 0.5gm
Bromcresol Purple 32.0mg

Final pH 6.9 +/- 0.3 at 25ºC.

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


Storage: Upon receipt store at 2-30ºC. away from direct light. Media should not be used if there are any signs of deterioration (shrinking, cracking, or discoloration), contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat and freezing.



Clinical specimens: Inoculate medium with a pure culture. Incubate medium aerobically at 35 degrees C. for 24-48 hours. Observe for turbidity and color change in the medium. This product is used in conjunction with other biochemical tests to identify cultures of isolated organism.

Samples of water and other material: Directly inoculate sample into the medium. Incubate in an aerobic atmosphere at 45.5ºC. for 24-48 hours. Observe for turbidity and color change in the medium. This product is used in conjunction with other biochemical tests to identify cultures of isolated organism.


A positive reaction for the presence of group D enterococci is indicated by turbidity and a color change in the medium from purple to yellow. A negative reaction is indicated by absence of growth and a purple color.


Enterococci will usually result in heavy growth and a color change within 24 hours; some strains, however, take 48 hours while others grow with no color change even aft 72 hours. (6)


Standard microbiological supplies and equipment such as loops, other culture media, swabs, applicator sticks, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Enterococcus faecalis
ATCC ® 29212
E 24-48hr 35°C Aerobic Growth; broth turns yellow
Streptococcus pyogenes
ATCC ® 19615
E 24-48hr 35°C Aerobic< Inhibited; broth remains purple

User Quality Control


SF Broth should appear clear, and purple in color.

E. faecalis growing in SF Broth

Enterococcus faecalis (ATCC ® 29212) growing in SF Broth (Cat. no. K45). The color change to yellow is indicative of dextrose fermentation. Incubated aerobically for 24 hours at 35ºC.

S. pyogenes inhibited in SF Broth

Streptococcus pyogenes (ATCC ® 19615) inhibited in SF Broth (Cat. no. K45). Incubated aerobically for 24 hours at 35ºC.


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

3. Hanja and Perry. 1943. Am. Jour. Publ. Health.; 33:550.

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

5. MacFaddin, J.F. Biochemical Tests for Identification of Medical Bacteria,, Lipincott Williams & Wilkins, Philadelphia, PA.

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

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

8. APHA Technical Committee on Microbiological Methods for Foods. Compendium of Methods for the Microbiological Examination of Foods, APHA, Washington, D.C.

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