Staphylococcus aureus · MPN enrichment · granulated
Tryptic Soy Broth with Sodium Chloride – 10 % NaCl broth for S. aureus MPN
Tryptic Soy Broth with 10 % sodium chloride is the enrichment broth of the MPN procedure for Staphylococcus aureus described in FDA BAM Chapter 12. It is used for foods in which small numbers of staphylococci are expected among a large accompanying flora.
- 10 % NaCl for selective MPN enrichment
- Positive tubes streaked on Baird-Parker Agar
- Granulated – less dust, better flow
How Tryptic Soy Broth with Sodium Chloride works
Casein and soy peptones provide nutrients, and the high salt concentration suppresses most bacteria other than staphylococci. Tubes from three dilutions are incubated, growth is streaked on Baird-Parker Agar, and typical colonies are confirmed with the coagulase test. The number of positive tubes gives the MPN.
Typical reactions
| Organism | Reaction |
| S. aureus | Growth; black colonies with clear halo on Baird-Parker Agar |
| E. coli | Suppressed |
Technical data
| Preparation | 135 g/L; boil to dissolve; autoclave 121°C 15 min |
| Final pH | 7.3±0.2 |
| Incubation | 35-37°C for 24 h (QC) |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years unopened |
Applications and practical notes
Enrichment broths with a high salt content are used when low numbers of Staphylococcus aureus are expected, for example in the MPN procedures of ISO 6888-3 and FDA BAM Chapter 12. Typical applications include:
- Detection of low numbers of S. aureus in processed foods
- MPN counts of coagulase-positive staphylococci
- Recovery of salt-tolerant staphylococci from mixed flora
- Dairy, meat and ready-to-eat food laboratories
Working with Tryptic Soy Broth with Sodium Chloride: Prepare the tubes from three consecutive dilutions and record which tubes give confirmed S. aureus, because only these count for the MPN.
Good practice with dehydrated media: keep the bottle tightly closed in a cool, dry place, weigh the powder quickly to avoid moisture uptake, and use fresh distilled or deionised water. Check the pH of each new batch after preparation and before use, and label prepared media with the date. Performance of each lot can be verified with reference strains according to ISO 11133, the standard for the preparation, production, storage and performance testing of culture media.
About the Staphylococcus aureus methods: coagulase-positive staphylococci in the food chain are counted on Baird-Parker Agar according to ISO 6888-1, and typical colonies are confirmed with the coagulase test. For low numbers, ISO 6888-3 uses an MPN technique with Giolitti-Cantoni Broth, and the FDA BAM Chapter 12 describes direct plating and an MPN method with Tryptic Soy Broth containing 10 % NaCl. In pharmaceutical microbiology, the test for S. aureus in EP 2.6.13 and USP <62> uses Mannitol Salt Agar. COLO.Science offers media, supplements, rapid tests, identification kits and QC strains for every step.
Complete sets from one supplier: COLO.Science supplies culture media, supplements, rapid tests, identification kits and QC strains as complete sets for the method you follow. Send us your sample types and standards, and we will prepare an offer with the matching products and documentation.
Tryptic Soy Broth with Sodium Chloride is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Tryptic Soy Broth with Sodium Chloride, please send us a request. With every delivery of Tryptic Soy Broth with Sodium Chloride you receive the lot number and expiry date, and on request we send the available documentation for Tryptic Soy Broth with Sodium Chloride.
Where Tryptic Soy Broth with Sodium Chloride fits in Staphylococcus aureus testing
- Colony count – Baird-Parker Agar with Egg Yolk Tellurite Emulsion (ISO 6888-1); alternatives: chromogenic S. aureus agar or Vogel-Johnson Agar
- Low numbers (MPN) – Giolitti-Cantoni Broth (ISO 6888-3) or Tryptic Soy Broth with 10 % NaCl (FDA BAM), then plating on Baird-Parker Agar
- Confirmation – coagulase test with Rabbit Plasma, latex kit or DNase Agar
- Pharmaceutical products – Mannitol Salt Agar for the S. aureus test of EP 2.6.13 / USP <62>; QC strains for media testing
See the complete Staphylococcus set in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Tryptic Soy Broth with Sodium Chloride 10%, granulated | PRO7625 | 250 g |
Product notice: preparation, storage conditions and shelf life are given on the label. Technical data on this page are for orientation; the label and the lot documentation apply. B2B prices are quoted net, excluding VAT.
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Send the sample type, target organism and the standard you follow. COLO.Science will put together the media, supplements, QC strains and confirmation tests for the whole procedure.
