A-1 Broth
Also known as：A-1 · A-1 Medium · A1 Broth · A-1 Medium for Fecal Coliforms
For the detection and enumeration of fecal coliforms in seawater, estuarine water, and shellfish by the most probable number method.
- Category
- Dehydrated Culture Media
- Dissolve per litre
- 31.5 g
- Pack sizes
- 500 g · 5 kg · 25 kg
- Certifications
- ISO 22000 · Non-GMO
Data updated：2026-11-06
Overview
A-1 Broth is a broth (liquid) medium, a selective medium for food and clinical testing that suppresses competing flora and makes target colonies recognisable. It is used for rapid faecal coliform testing of water and shellfish. STBIO manufactures it from food-grade raw materials in an ISO 22000 certified facility, with a COA for every batch.
Principle
A-1 Broth was developed by Andrews and Presnell for the rapid recovery of fecal coliforms from estuarine water, eliminating the need for a presumptive enrichment step before confirmation.¹ Tryptone supplies nitrogen, amino acids, and peptides, while lactose and salicin serve as fermentable carbohydrates. Sodium chloride maintains the osmotic balance. Triton X-100, a non-ionic surfactant, suppresses the growth of non-fecal organisms and assists the recovery of stressed coliforms from marine samples. Tubes are incubated at 35°C for 3 hours to allow resuscitation of injured cells, and then transferred to a water bath at 44.5°C for a further 21 hours. At the elevated temperature, only thermotolerant (fecal) coliforms ferment lactose with the production of gas. The presence of gas in the Durham tube after incubation constitutes a positive result, and fecal coliform densities are calculated from the pattern of positive tubes using most probable number tables.²
How selective media fit into the testing workflow
Pathogen testing normally runs in three stages: a pre-enrichment medium such as Buffered Peptone Water repairs injured cells and raises numbers, a selective enrichment then suppresses competing flora, and finally a selective differential agar isolates the target colonies. Selective agents are typically bile salts, dyes, or antibiotics; differential agents make target colonies develop a characteristic colour or morphology. Choose the combination specified by the method you follow.
Directions
Suspend 31.5 g of powder in 1 L of purified water. Heat with continuous stirring and bring to the boil for 1 minute. Dispense into tubes containing inverted Durham tubes. Sterilize by autoclaving at 121°C for 10 minutes. Test the finished medium for performance using stable, standard control cultures.
Cultural response
| Test organism | ATCC | Growth |
|---|---|---|
| Escherichia coli | 25922 | good-luxuriant |
| Enterobacter aerogenes | 13048 | good |
Product highlights
- Food-grade raw materials, produced in an ISO 22000 certified facility
- Manufactured to the standard formulation, 31.5 g per litre
- Performance verified against standard control strains before release (Escherichia coli, Enterobacter aerogenes)
- Non-GMO
- 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
01Can selective media be autoclaved?
Not always. Some media containing dyes or selective inhibitors lose their selectivity if overheated and should only be heated until fully dissolved, without autoclaving. Follow the preparation instructions for this product, and contact us if you are unsure.
02How much powder per litre?
Use 31.5 g per litre of deionised water; preparation and sterilisation conditions are given on the specification sheet.
03Which organisms is it suitable for?
Coliforms, Gram-negative, E. coli, Escherichia coli, Enterobacter aerogenes. See the cultural response table and the specification sheet.
04Is the raw material non-GMO?
Yes. The raw material is non-GMO; the supplier declaration can be provided with the COA.
05Can 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.
06How is this product prepared?
Suspend 31.5 g of powder in 1 L of purified water. Heat with continuous stirring and bring to the boil for 1 minute. Dispense into tubes containing inverted Durham tubes. Sterilize by autoclaving at 121°C for 10 minutes. Test the finished medium for performance using stable, standard control cultures.
07How 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. Andrews W. H. and Presnell M. W., 1972. Rapid recovery of Escherichia coli from estuarine water. Appl. Microbiol., 23:521-523.
- 2. American Public Health Association, Standard Methods for the Examination of Water and Wastewater, current edition, APHA Press, Washington, D.C.