Baird Staphylococcus Enrichment Broth

Baird Staphylococcus Enrichment Broth

Selective Enrichment Medium for Recovery of Staphylococcus aureus

Catalog Number: AS-1131

Overview

Baird Staphylococcus Enrichment Broth is a highly selective liquid enrichment medium designed for the recovery of low numbers and stressed cells of coagulase-positive staphylococci, particularly Staphylococcus aureus, from foods, cosmetics, and environmental samples with heavy background flora.

The formulation supports resuscitation of heat-, freeze-, or acid-injured cells through the inclusion of sodium pyruvate and glycine, while selectivity is achieved by lithium chloride and potassium tellurite added as supplements. This broth is the official enrichment step in ISO 6888-3 for detection of S. aureus at contamination levels below 100 CFU/g or mL, prior to plating on selective agar such as Baird-Parker Agar.

Ausamics Baird Staphylococcus Enrichment Broth delivers high recovery efficiency, strong selectivity, and reproducible performance for routine and reference microbiology laboratories.

Key Features & Benefits

• High resuscitation capacity for injured Staphylococcus cells

• Strong inhibition of competing Gram-negative bacteria and background flora

• Selective enrichment prior to plating on Baird-Parker Agar

• Characteristic blackening due to tellurite reduction

• International reference enrichment broth (ISO 6888-3)

Typical Applications

Food Microbiology

• Enrichment of Staphylococcus aureus from foods with high background flora

• Detection of low-level contamination in processed and ready-to-eat foods

Pharmaceutical & Cosmetic Testing

• Screening of raw materials and finished products

• Hygiene monitoring and contamination investigation

Environmental & Research Laboratories

• Recovery of stressed staphylococci from environmental samples

• Reference and method-validation workflows

Principle of the Medium

The nutrient base supports staphylococcal growth while selective agents suppress competing organisms:

• Sodium pyruvate and glycine promote recovery of stressed or injured cells

• Lithium chloride inhibits many Gram-positive competitors

• Potassium tellurite suppresses Gram-negative bacteria and enables visual indication

Tellurite reduction by S. aureus typically results in blackening of the medium, with additional reactions observable when egg-yolk emulsion is present. Enriched cultures are subsequently plated onto selective agar for presumptive identification.

Composition (Typical, Base Only – per litre)

• Tryptone: 10.0 g

• Meat extract: 5.0 g

• Yeast extract: 1.0 g

• Sodium pyruvate: 10.0 g

• Glycine: 12.0 g

• Lithium chloride: 5.0 g

Final pH at 25 °C: 7.0 ± 0.2

Supplements (Added After Sterilisation)

• Egg-yolk emulsion (50 %): 50 mL/L

• Potassium tellurite (1 % solution): 1.0–2.0 mL/L
  (Final concentration: 0.001–0.002 %)

Preparation (Typical)

• Suspend 43.0 g dehydrated base in 950 mL purified water

• Heat to boiling until completely dissolved

• Autoclave at 121 °C for 15 minutes

• Cool to 50–55 °C

• Aseptically add sterile egg-yolk emulsion and filter-sterilised potassium tellurite

• Mix gently and dispense into sterile tubes or flasks

Incubation & Interpretation

Incubation

• 35–37 °C for 24–48 hours

• Examine at 24 h and again at 48 h

Typical Positive Reaction

• Blackening of the broth due to tellurite reduction

• Clearing around egg-yolk particles may be observed

Enriched cultures should be subcultured onto Baird-Parker Agar or equivalent selective media for further evaluation.

Storage & Stability

Dehydrated base

• Store below 30 °C, dry, tightly sealed

Prepared complete broth

• Store at 2–8 °C, protected from light

• Use within 7 days

Intended Use

For laboratory food, cosmetic, environmental, and research microbiology use only.

Not for human, animal, diagnostic, or therapeutic use.

Quality & Compliance

• Official enrichment broth in ISO 6888-3

• Widely referenced in national and international standards

• Manufactured under controlled conditions for batch consistency

• Certificate of Analysis (COA) available

• Safety Data Sheet (SDS) available upon request