Schaedler Broth

Schaedler Broth is excellent for the primary isolation of anaerobes, for blood cultures and other materials. It is useful for the determination of the minimum inhibitory concentration (MIC) of antimicrobials used in sensitivity tests. The solid medium is not used to perform sensitivity tests because there is no effective agreement between the concentration of the drug and the diameters of the zones of inhibition that are observed when the solid medium is used.

TSB Broth, casein peptone and meat peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly the B-group. Dextrose is the fermentable carbohydrate providing carbon and energy. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Tris (hydroxymethyl aminomethane) is used to buffer the medium. Hemin stimulates organism growth. L-Cystine is a reducing agent.

The addition of sodium polyanethol-sulphonate (SPS) and carbon dioxide to Schaedler Broth enables it to be used as a blood culture medium and for the cultivation of especially fastidious Bacteroides species.

Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.

Preparation

Suspend 28.4 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 15 minutes.

Determination of the MIC (Fass et al.)

1. Place a glass bead of 6 mm in diameter at the bottom of the test tube before sterilizing.
2. Observe the bacterial growth after 18-24 hours of incubation at 35 ± 2 °C.

Cultivation of anaerobic cocci

1. It is recommended to add 1 mL of inactivated horse serum for every 100 mL of broth.
2. Inoculate the specimen into the tube and incubate in anaerobic conditions for 18-24 hours for up to 7 days.
3. Growth in the tubes is indicated by the presence of turbidity.

Note: in order to know if the Schaedler Broth that has been stored has deteriorated or oxidized, add 0.01 grams of resazurin for each 100 mL of the medium.

• Fass R.J., Prior R.B. and Rotille C.A. 1975. Antimicrobial Agents Chemother. 8, 444-452.
• Rotille C.A. and Col. 1975. Antimicrob. Agents Chemother. 7. 311-315.
• Isenberg HD. (ed) 1992. Clinical microbiology procedures handbook. American Society for Microbiology, Washington, DC.
• Atlas RM. 1993. Handbook of microbiological media, p. 794-795. CRC Press, Boca Raton, FL.