"F" in selenite F broth indicates:
Selenite F Broth:
It is a liquid culture media and used as a selective medium for the isolation of Salmonella species from feces, urine, water, food, and other material. It is an example of enrichment media as it favors the multiplication of the targeted organism by suppressing the competitors. Leifson fully investigated the inhibitory effects of selenite and formulated the media.
Composition of Selenite F Broth:
1. Casein enzymic hydrolysate: 5 g/l
2. Lactose: 4 gm/L
3. Sodium phosphate: 10 gm/L
4. Sodium hydrogen selenite: 4 gm/L
Functions of each component:
1. Casein enzymic hydrolysate:
It provides nitrogenous substances, carbon compounds, and vitamin sources
It maintains the Ph of the media by neutralizing the alkali produced by the bacteria when they reduce the selenite.
3. Sodium phosphate:
It helps to maintain a stable pH and also lessens the toxicity of selenite this increases the capacity of the media.
4. Sodium selenite:
It inhibits many species of gram-positive and gram-negative bacteria including enterococci and coliforms without affecting the salmonella. Sodium selenite is highly toxic at near-neutral Ph.
This broth should not be incubated for more than 24 hours as the inhibitory effect of selenite decreases after 6 - 12 hours of incubation.
Do not autoclave this broth instead sterile this medium under pressure at 100°C for 10 minutes.
"F" in the selenite F Broth indicates "Faeces"
Uses of Selenite F Broth:
- It is used as a selective enrichment for the cultivation of Salmonella species.
- It is also used for the isolation of some species of Shigella.
- This broth can also be used as the transport medium for strains of Vibrio cholera as this organism can survive 2 to 5 days in Sodium Selenite Broth.
Interpretation of growth on Selenite F Broth:
Growth is interpreted by the appearance of colorless, turbidity in the medium.