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AuSaMicS AS-1346 Selenite Cystine Broth 500g dehydrated enrichment media for Salmonella.
  • AuSaMicS AS-1346 Selenite Cystine Broth 500g dehydrated enrichment media for Salmonella.
Selenite Cystine Broth (AS_1346)

Selenite Cystine Broth (AS_1346)

$35.00 AUD
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AuSaMicS Life Science • Selective Salmonella Enrichment

Selenite Cystine Broth

Enhanced Selective Enrichment for Injured & Stressed Salmonella

Selenite Cystine Broth is a highly selective enrichment medium formulated for the recovery of Salmonella spp. from food, environmental, and clinical samples. The combination of sodium selenite and L-cystine helps suppress competing flora while improving recovery of injured, stressed, or low-level target organisms prior to plating on selective isolation media.

AS-1346 Selective Enrichment Australian Stock Salmonella Recovery
Application: Food, environmental & clinical enrichment Best for: Injured or stressed Salmonella Workflow: Enrichment before XLD, BGA, SS or chromogenic media

Salmonella Enrichment Specialist

High recovery for injured and stressed cells
L-cystine support for compromised organisms
Rapid enrichment in short incubation windows
Food microbiology ready
COA support available
Selective Principle
Selenite suppresses many competing enterics while permitting Salmonella enrichment

Overview & Applications

Selenite Cystine Broth is an enhanced selective enrichment medium for Salmonella spp., especially useful when target cells may be present in low numbers or have been stressed by refrigeration, drying, chemical exposure, or other processing conditions.

The addition of L-cystine improves recovery of damaged cells, while sodium selenite maintains selective pressure against many competing coliforms and other background flora. The broth is commonly used as an intermediate enrichment step before subculture onto selective and differential agar media.

Primary Applications
  • Recovery of injured or stressed Salmonella
  • Food testing: eggs, poultry, dairy, spices, feeds
  • Environmental monitoring workflows
  • Clinical and public health microbiology screening
  • Pre-enrichment before plating on selective agar
Key Features
  • Sodium selenite for selective suppression
  • L-cystine to enhance recovery of stressed cells
  • Rapid enrichment typically within 6–18 hours
  • Useful where more aggressive enrichment systems may over-inhibit
  • Compatible with standard Salmonella isolation workflows

Complete Selenite Cystine Formulation

Composition (per Liter)

Component Amount Primary Function Practical Benefit
Tryptone 5.0 g Nitrogen and nutrient source Supports early recovery and multiplication of target organisms
Lactose 4.0 g Carbohydrate source Helps reduce selenite toxicity during enrichment
L-Cystine 0.01–0.05 g Recovery enhancer Improves viability of injured or stressed Salmonella
Sodium Hydrogen Phosphate 10.0 g Buffering system Maintains suitable pH during short enrichment
Sodium Selenite 4.0 g Selective agent Suppresses many competing enteric bacteria
Final pH: 7.0 ± 0.2 at 25°C

Preparation, Incubation & Interpretation

Preparation

  1. Suspend 23.01–23.05 g in 1 L of purified or distilled water.
  2. Warm gently with agitation until dissolved.
  3. Do not autoclave, as selenite may decompose and reduce performance.
  4. Dispense aseptically into sterile tubes, bottles, or enrichment vessels.
  5. Use freshly prepared broth for optimal selectivity and recovery.

Incubation

  • Temperature: 35–37°C
  • Duration: typically 6–18 hours
  • Do not exceed 24 hours, as prolonged exposure may become inhibitory even to target organisms
  • Subculture promptly after enrichment

Interpretation

  • Positive enrichment: visible turbidity or evidence of growth in the broth
  • This is an enrichment medium, not a direct differential confirmation broth
  • Subculture onto XLD Agar, Brilliant Green Agar, SS Agar, Hektoen, or suitable chromogenic Salmonella agar
  • Interpret final results in combination with colony morphology, biochemical confirmation, and serological or molecular testing as required

Comparative Salmonella Enrichment & Isolation Workflow

Medium / Step Primary Purpose Selectivity Best Use Case Key Advantage
Selenite Cystine Broth (AS-1346) Selective enrichment Moderate to high Injured, stressed, or low-level Salmonella Improved recovery with L-cystine support
Rappaport-Vassiliadis Broth Selective enrichment High Robust Salmonella strains in food workflows Strong selectivity against competing flora
Buffered Peptone Water Pre-enrichment Low / non-selective Resuscitation before selective enrichment Gentle recovery of injured organisms
XLD Agar Selective isolation High Post-enrichment plating Differential colony appearance with H₂S indication
Brilliant Green Agar / SS Agar Selective isolation High Secondary plating and confirmation workflows Strong inhibition of competing flora

Recommended Salmonella Detection Workflow

1. Pre-Enrichment
Use Buffered Peptone Water when samples may contain heavily stressed cells
2. Selective Enrichment
Transfer to Selenite Cystine Broth for selective multiplication of target organisms
3. Selective Plating
Subculture onto XLD, BGA, SS, or chromogenic Salmonella agar
4. Confirmation
Confirm by biochemical, serological, or molecular methods
Practical note: Selenite Cystine Broth is especially useful when target cells may be sublethally injured and require a gentler selective enrichment step than more aggressive alternatives.

Strategic Use of Selenite Cystine Broth

Key Advantages

  • Improved recovery of injured or stressed Salmonella
  • Useful for low-level contamination workflows
  • Well suited to food microbiology and public health testing
  • Compatible with multiple downstream plating media
  • Rapid enrichment compared with longer broth workflows

Method Considerations

  • Do not autoclave the completed broth
  • Excessive incubation can reduce target recovery
  • Broth turbidity is presumptive only and requires subculture
  • Background flora suppression may vary with sample type and load

Selection Guide

  • Use when Salmonella may be stressed or damaged
  • Choose as a selective enrichment before XLD or BGA plating
  • Consider alongside pre-enrichment for highly processed samples
  • Useful where stronger enrichment systems may over-inhibit

Quality Control & Performance Standards

Positive Control:
Salmonella Typhimurium — expected good enrichment / turbidity
Negative Control:
Escherichia coli — expected inhibited or minimal growth
Reference Standards:
FDA-BAM, USP <62>, EP 2.6.13, APHA
Documentation:
Certificate of Analysis and lot-specific QC data available on request

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