Antibiotic Medium 3
Also known as：Antibiotic Medium No. 3 · Antibiotic Assay Broth · Antibiotic Assay Medium No. 3 · Assay Broth
For the microbiological assay of antibiotics by the turbidimetric method and for the preparation of test organism inocula, in accordance with the United States Pharmacopeia.
- Category
- Dehydrated Culture Media
- Dissolve per litre
- 17.5 g
- Pack sizes
- 500 g · 5 kg · 25 kg
- Certifications
- ISO 22000 · Halal
Data updated：2026-11-07
Overview
Antibiotic Medium 3 is a broth (liquid) medium, one of the numbered pharmacopoeial media for antibiotic potency assays. It is specified by the pharmacopoeia for particular antibiotics and test organisms in potency assays; numbers are not interchangeable. STBIO manufactures it from food-grade raw materials in an ISO 22000 certified facility, with a COA for every batch. This is the Halal-certified version.
Principle
Antibiotic Medium 3 is the liquid assay medium specified by the United States Pharmacopeia for the turbidimetric assay of antibiotics.¹ Beef extract, yeast extract, and peptone supply nitrogen, vitamins, and growth factors, and dextrose provides the carbon and energy source. Sodium chloride maintains the osmotic equilibrium, and the potassium phosphate buffer holds the pH within the narrow range required for consistent antibiotic activity. In the turbidimetric assay, the test organism is grown in the presence of graded concentrations of the antibiotic, and growth is measured photometrically after a short incubation period; the inhibition of growth is proportional to the antibiotic concentration. Because the response is read as turbidity, the medium must be clear and free from particulate matter. The broth is also used to grow test organisms for the preparation of standardised inocula for cylinder-plate assays.²
Antibiotic potency assay media
Antibiotic potency assays measure activity through the response of a test organism, and each antibiotic and assay method calls for a specific numbered medium taken from the pharmacopoeial formulations. Select the number specified by the pharmacopoeial chapter and method you follow; the media are not interchangeable.
Directions
Suspend 17.5 g of powder in 1 L of purified water. Heat with continuous stirring and bring to the boil for 1 minute. Dispense into tubes or flasks. Sterilize by autoclaving at 121°C for 15 minutes. Test the finished medium for performance using stable, standard control cultures.
Product highlights
- Food-grade raw materials, produced in an ISO 22000 certified facility
- Halal certified, suitable for the Malaysian, Indonesian, and Middle Eastern markets
- Manufactured to the standard formulation, 17.5 g per litre
- Available in 500 g / 5 kg / 25 kg, from laboratory to industrial scale
- COA, specification sheet, and technical data sheet available; samples on request
- Manufactured in Taiwan with reliable supply
Food grade versus laboratory grade
Most culture media suppliers use laboratory-grade raw materials, which are held to lower standards for heavy metal residues, microbial contamination control, and traceability. That is adequate for pure research but not for applications with stricter raw-material requirements. STBIO manufactures with food-grade raw materials throughout, in a facility certified to ISO 22000 food safety management.
- Food microbiology laboratories working to ISO 17025 or equivalent requirements
- Biotech manufacturers exporting fermentation products and needing full raw-material traceability
- Organisations with ESG or compliance audit requirements across their supply chain
- Companies sourcing both Halal and non-Halal products who need one consistent material grade
Frequently asked questions
01How much powder per litre?
Use 17.5 g per litre of deionised water; preparation and sterilisation conditions are given on the specification sheet.
02Which organisms is it suitable for?
Gram-positive, Gram-negative. See the cultural response table and the specification sheet.
03Can it be used for food-grade applications?
Yes. It is made from food-grade raw materials in an ISO 22000 certified facility and is suitable for culturing starters for fermented products that are consumed directly.
04How is this product prepared?
Suspend 17.5 g of powder in 1 L of purified water. Heat with continuous stirring and bring to the boil for 1 minute. Dispense into tubes or flasks. Sterilize by autoclaving at 121°C for 15 minutes. Test the finished medium for performance using stable, standard control cultures.
05Is there a non-Halal version?
Yes. This is the Halal certified version; an equivalent standard version is also available.
06How do I request a bulk quotation, and can you provide a COA?
Yes. This product is available in 500 g, 5 kg, 25 kg. Tell us your application and volume when requesting a quotation; we reply within one working day and can supply the COA, specification sheet, and technical data sheet.
Used in these applications
References
- 1. United States Pharmacopeia, current edition. Chapter <81> Antibiotics — Microbial Assays, USP-NF, Rockville, MD.
- 2. Grove D. C. and Randall W. A., 1955. Assay Methods of Antibiotics: A Laboratory Manual, Medical Encyclopedia, New York.