Primary Applications

• Primary enrichment of Salmonella from food and feed
• Stool, sewage, and environmental samples
• Pharmaceutical and water QC screening
• Routine Salmonella workflows in food microbiology labs
• Part of standard multi-step enrichment protocols

Key Features

• Sodium selenite selectively inhibits many competing coliforms
• Supports recovery of sublethally injured Salmonella
• Buffered system helps maintain suitable enrichment conditions
• Fast enrichment typically within 6–18 hours
• Compatible with ISO, FDA-BAM, USP and related workflows

Component	Amount	Primary Function	Practical Role
Peptone	5.0 g	Nutrient source	Supports growth and recovery of target organisms
Lactose	4.0 g	Carbohydrate source	Helps moderate selenite toxicity during enrichment
Sodium Phosphate (dibasic)	10.0 g	Buffering system	Helps maintain pH stability
Sodium Hydrogen Phosphate (monobasic)	1.0 g	Buffering adjustment	Supports appropriate enrichment environment
Sodium Selenite	4.0 g	Selective agent	Suppresses many competing Enterobacteriaceae and fecal flora

Final pH: 7.0 ± 0.2 at 25°C

Preparation

1. Suspend 20 g of dehydrated medium in 1 L purified or distilled water.
2. Warm gently with agitation until dissolved.
3. Do not overheat, as selenite is heat-labile and excessive heating reduces performance.
4. Dispense into tubes or bottles.
5. Autoclaving is not recommended. Use a boiling water bath for about 10 minutes or follow validated manufacturer instructions.
6. Cool to room temperature before inoculation.

Incubation

• Temperature: 35–37°C
• Duration: 6–24 hours
• Subculture promptly after enrichment
• Do not incubate beyond 24 hours, since prolonged exposure may inhibit even target organisms

Interpretation

• Selenite Broth is an enrichment medium and is not directly differential.
• After incubation, streak onto selective plating media such as XLD Agar, Hektoen Enteric Agar, Brilliant Green Agar, or Bismuth Sulfite Agar.
• Final presumptive interpretation is based on colony morphology on plated media and subsequent confirmatory testing.

Selective Agar	Typical Salmonella Appearance	Why Use It
XLD Agar	Red colonies with black centers	Good differential performance with H₂S indication
Hektoen Enteric Agar	Blue-green colonies, often with black centers	Useful for enteric differentiation
Brilliant Green Agar	Pink to white colonies in a red medium	Strong suppression of many competing flora
Bismuth Sulfite Agar	Black colonies with metallic sheen	Useful for selective recovery of certain Salmonella types

Standards note: Selenite Broth remains widely recognized in major Salmonella enrichment workflows used in food, pharmaceutical, and public health microbiology.

Key Advantages

• Classical, widely recognized enrichment medium
• Good selective suppression of many competing fecal organisms
• Fast enrichment for routine screening workflows
• Compatible with multiple downstream selective agars
• Suitable for food, water, clinical, and environmental applications

Method Considerations

• Sodium selenite is toxic and must be handled carefully
• Do not autoclave; overheating reduces selectivity
• Not a differential medium — requires downstream plating
• Over-incubation may inhibit target recovery

Selection Guide

• Use for routine short-term selective enrichment of Salmonella
• Best when paired with downstream XLD, HEA, BGA, or BS plating
• Suitable for classical food microbiology and stool culture workflows
• Use validated laboratory SOPs for heating and handling

Positive Control:
Salmonella Typhimurium — expected enrichment growth

Negative / Inhibition Check:
Escherichia coli, Klebsiella, Enterobacter — expected reduced recovery relative to target organisms

Referenced In:
ISO 6579-1, FDA-BAM, USP <61>/<62>, WHO, ICMSF

Documentation:
Certificate of Analysis and lot-specific QC data available on request