Thermo Scientific™ Oxoid™ Selenite Cystine Broth Base

Selenite Cystine Broth Base is a modified enrichment medium used for the selective isolation of Salmonella spp. from fecal samples, food products, and other materials. It is based on Leifson's formula, enhanced with the addition of L-cystine, which helps reduce the toxicity of selenite, making it more efficient for Salmonella isolation while limiting the growth of competing organisms.

Key Features

1. Selective Enrichment:
   • Designed to inhibit non-target organisms while promoting the growth of Salmonella.
   • Meets the requirements of the AOAC, APHA, and USP for Salmonella detection.
2. Enhanced Formula:
   • The addition of L-cystine reduces selenite's toxicity to microorganisms, providing a balanced selective medium.
3. Broad Applications:
   • Suitable for testing feces, foodstuffs, dairy products, and environmental samples.
   • Recommended for food safety and clinical diagnostic laboratories.

Typical Composition (g/L)

Preparation Instructions

1. Sodium Biselenite Solution:
   • Dissolve 4 g of sodium biselenite (LP0121) in 1 L of distilled water.
2. Broth Base:
   • Add 19 g of Selenite Cystine Broth Base to the sodium biselenite solution.
   • Warm gently to dissolve and mix thoroughly.
3. Sterilization:
   • Sterilize in free-flowing steam for 15 minutes.
   • DO NOT AUTOCLAVE, as selenite may degrade under high pressure and temperature.

Applications

1. Clinical Microbiology:
   • Enrichment of Salmonella spp. from fecal samples in diagnostic testing.
2. Food Safety Testing:
   • Detection of Salmonella spp. in food products, including dairy and processed foods.
3. Environmental Testing:
   • Recovery of Salmonella spp. from environmental samples like sewage and water.

Technique and Usage

1. Sample Inoculation:
   • Add 1-2 g of solid sample to 10-15 mL of the medium.
   • For liquid samples, use double-strength broth and mix in a 1:1 ratio.
2. Incubation:
   • Incubate at 35-37°C for 12-24 hours.
   • For some samples, incubation at 43°C may enhance selectivity.
3. Subculture:
   • Transfer to selective agar plates, such as MacConkey or XLD agar, for further isolation and identification.

Storage and Stability

• Dehydrated Medium:
  • Store at 10-30°C in a sealed, dry container.
• Prepared Medium:
  • Store at 2-8°C, protected from light.
• Use before the expiry date on the label.

Appearance

Quality Control

Precautions

1. Toxicity of Sodium Biselenite:
   • Handle with care; toxic by inhalation or ingestion.
   • Follow safety protocols and use personal protective equipment.
2. Prepared Medium Stability:
   • Discard if red precipitate (reduced selenite) forms at the bottom.
3. Incubation Guidelines:
   • Do not incubate longer than 24 hours, as selenite's selective effect diminishes after 6-12 hours.

Advantages

1. Improved Selectivity:
   • L-cystine minimizes toxicity, improving recovery rates for Salmonella spp.
2. Compliant with Standards:
   • Approved by AOAC, APHA, and USP for Salmonella testing.
3. Versatile Applications:
   • Suitable for a variety of sample types and testing workflows.

Applications Summary

• Clinical Diagnostics: Enriches and isolates Salmonella spp. from patient samples.
• Food Safety: Detects Salmonella spp. contamination in food and dairy products.
• Environmental Testing: Monitors Salmonella spp. in water and other environmental samples.

Selenite Cystine Broth Base is a reliable and effective tool for laboratories focused on food safety, clinical diagnostics, and environmental microbiology. Let me know if you need further details or related resources!