Skip to product information
Request a Quote
A1 Broth Medium AS-1101 for Coliform Testing - Ausamics
$45.00 AUD
A1 Medium
Multiple-Tube Fermentation Broth for Coliform & Faecal Coliform Detection in Water | Cat. No. AS-1101
Cat. No. AS-1101 pH 6.9 ± 0.2 31.5 g/L 121°C / 10 min ✓ ISO 9308-2:2012 ✓ APHA Standard Methods 🇦🇺 Made in Melbourne ⚡ Same-Week Dispatch
Cat. No.
AS-1101
pH (25°C)
6.9 ± 0.2
Dissolution
31.5 g/L
Autoclave
121°C / 10 min
Standard
ISO 9308-2
📄 Full DocumentationCOA, TDS & SDS every batch
🇦🇺 Australian StockNo import delays
⚡ Same-Week DispatchMelbourne warehouse
🔬 Technical SupportDirect from our team
Overview & Principle
A1 Medium (AS-1101) is a selective enrichment broth used for the Most Probable Number (MPN) detection of total coliforms and faecal coliforms in water, wastewater, and shellfish samples. It is the standard medium referenced in ISO 9308-2:2012 and APHA Standard Methods for the Examination of Water and Wastewater.
The medium uses lactose as the fermentable carbohydrate — coliform bacteria ferment lactose producing acid and gas, detected visually by gas collection in Durham (inverted fermentation) tubes. Triton X-100 (1 mL/L) is a non-ionic surfactant that suppresses Gram-positive flora without inhibiting coliform growth, providing selectivity. Salicin (0.5 g/L) further supports growth of faecal coliforms and E. coli.
✅ Positive result: Gas production in Durham tube within 24–48h = coliforms present.
❌ Negative result: No gas = coliforms absent at that dilution.
🕐 Faecal coliforms: Incubate at 44.5°C (instead of 35°C) — gas production confirms faecal coliforms (E. coli).
❌ Negative result: No gas = coliforms absent at that dilution.
🕐 Faecal coliforms: Incubate at 44.5°C (instead of 35°C) — gas production confirms faecal coliforms (E. coli).
Applications
💧
Drinking Water
Potable water coliform testing
🌊
Wastewater
Effluent coliform MPN
🦪
Shellfish
Faecal coliform in shellfish
🌋
Recreational Water
Swimming pools, beaches
🏭
Industrial Water
Process water monitoring
🌿
Environmental
River, groundwater monitoring
Selectivity — How Each Component Works
| Ingredient | g / L | Function |
|---|---|---|
| Peptone from Casein | 20.0 | Rich nitrogen source — supports broad coliform growth |
| Lactose | 5.0 | Selective fermentable carbohydrate — coliforms ferment lactose → gas in Durham tube |
| Sodium Chloride (NaCl) | 5.0 | Osmotic balance |
| Salicin | 0.5 | Additional fermentable carbohydrate — supports faecal coliforms and E. coli |
| Triton® X-100 | 1.0 mL | Non-ionic surfactant — suppresses Gram-positive flora; improves coliform selectivity |
| Total | 31.5 g/L + 1 mL Triton X-100 | pH 6.9 ± 0.2 | Autoclave 121°C / 10 min |
⚠️ Autoclave 10 minutes only — not the standard 15 minutes. Over-sterilisation degrades lactose and reduces selectivity. This is per Merck/ISO specification.
MPN Method — Interpretation
| Temperature | Incubation | Target | Positive Result |
|---|---|---|---|
| 35 ± 0.5°C | 24–48h | Total coliforms | Gas in Durham tube |
| 44.5 ± 0.2°C | 24h | Faecal coliforms / E. coli | Gas in Durham tube |
ⓘ Double-strength (2x) broth: For 10 mL water sample volumes, prepare double-strength A1 Medium (63 g/L) so the final concentration after adding the sample remains correct. Single-strength is used for 1 mL sample volumes.
FAQs
❓ Why is the autoclave time 10 minutes and not 15?
Lactose degrades at 121°C and prolonged autoclaving reduces its concentration and fermentability. The ISO 9308-2 specification requires 10 minutes at 121°C to preserve lactose integrity and selectivity. Always follow this exactly.
❓ What is the role of Triton X-100?
Triton X-100 is a non-ionic surfactant (polyethylene glycol octylphenyl ether) that selectively inhibits Gram-positive bacteria while not significantly inhibiting Gram-negative coliforms. This improves the specificity of A1 Medium for coliform detection in environmental water samples.
❓ Is AS-1101 equivalent to Merck 1.01699?
Yes — AS-1101 is formulated to the same Merck specification: Peptone from casein 20g, Lactose 5g, NaCl 5g, Salicin 0.5g, Triton X-100 1mL, pH 6.9 ± 0.2. Full COA included with every batch.
❓ How long can prepared A1 Medium be stored?
Up to 1 week at room temperature in the dark (per Merck specification). Alternatively store at 2–8°C for up to 2 weeks. Protect from light as Triton X-100 is sensitive to UV. Discard if turbid before inoculation.
Cross-Reference / Equivalents
| Manufacturer | Product Name | Cat. No. |
|---|---|---|
| Merck Millipore | A1 Medium (A-1 Broth) | 1.01699 |
| HiMedia | A1 Broth | M804 |
| Neogen (Acumedia) | A-1 Broth | 7300A |
| Thermo Scientific | A1 Broth | CM1121 |
Related Products
Product Specifications
| Product Name | A1 Medium (A-1 Broth) |
| Catalogue Number | AS-1101 |
| Synonyms | A-1 Broth; A1 Broth; A1 Coliform Medium; Multiple-Tube Fermentation Broth |
| Medium Type | Selective liquid enrichment broth for coliform MPN detection |
| Dissolution | 31.5 g/L + 1 mL Triton X-100 per litre of distilled water |
| Final pH at 25°C | 6.9 ± 0.2 |
| Sterilisation | Autoclave 121°C for 10 minutes (not 15 — lactose degrades) |
| Appearance (powder) | Light beige, free-flowing homogeneous powder |
| Appearance (prepared) | Clear to slightly opalescent, yellowish |
| Storage (powder) | Dry, tightly sealed, below 25°C, away from light |
| Storage (prepared) | Up to 1 week at room temperature in the dark; or 2 weeks at 2–8°C |
| HS Tariff Code | 3821.00.00 |
Formula — Per Litre (Merck Specification)
| Ingredient | Amount / L | Role |
|---|---|---|
| Peptone from Casein | 20.0 g | Nitrogen source; supports broad coliform growth |
| Lactose | 5.0 g | Fermentable carbohydrate — gas production = positive coliform result |
| Sodium Chloride (NaCl) | 5.0 g | Osmotic balance |
| Salicin | 0.5 g | Supports faecal coliforms and E. coli growth |
| Triton® X-100 | 1.0 mL | Non-ionic surfactant — selective suppression of Gram-positive flora |
| Total (powder) | 31.5 g/L + 1 mL Triton X-100 | pH 6.9 ± 0.2 | 121°C / 10 min |
Preparation Protocol
1
Suspend 31.5 g of dehydrated A1 Medium in approximately 990 mL of distilled or deionised water.
2
Add 1 mL of Triton X-100. Mix thoroughly until completely dissolved.
3
Dispense into tubes containing inverted Durham (fermentation) tubes. Ensure Durham tube is fully submerged and free of air bubbles.
4
Autoclave at 121°C for exactly 10 minutes. Do not exceed 10 minutes — over-sterilisation degrades lactose.
5
Cool before use. Check Durham tubes are bubble-free. Inoculate with water sample and incubate at 35°C (total coliforms) or 44.5°C (faecal coliforms).
6
Double-strength broth for 10 mL samples: Dissolve 63 g/L + 2 mL Triton X-100 to achieve correct final concentration after sample addition.
Applicable Standards
| ISO 9308-2:2012 | Water quality — Enumeration of E. coli and coliform bacteria — Part 2: Most probable number method |
| APHA Standard Methods | Standard Methods for the Examination of Water and Wastewater — 9221 series (MPN method) |
| USEPA Method 1103.1 | Escherichia coli in water by membrane filtration (related MPN methodology) |
Literature & References
| # | Reference |
|---|---|
| 1 | Merck Microbiology Manual. A1 Medium, Cat. 1.01699. Merck KGaA; current edition. [Primary reference formula] |
| 2 | ISO 9308-2:2012. Water quality — Enumeration of Escherichia coli and coliform bacteria — Part 2: Most probable number method. Geneva: ISO; 2012. |
| 3 | APHA/AWWA/WEF. Standard Methods for the Examination of Water and Wastewater. 23rd ed. Section 9221. American Public Health Association; 2017. |
| 4 | Reasoner DJ, Blannon JC, Geldreich EE. Rapid seven-hour fecal coliform test. Appl Environ Microbiol. 1979;38:229–236. [A1 Broth for faecal coliform detection] |
📄 Full SDS available: 16-section GHS (Australian WHS Regulations 2023 / GHS 7th Edition) — support@ausamics.com.au
Hazard Identification (GHS 7th Ed / WHS 2023)
| GHS Classification | NOT classified as a hazardous substance under Australian WHS Regulations 2023. |
| Signal Word | None required |
| Triton X-100 note | Eye Irrit. 2 (H319) at high concentrations — not classified at 1 mL/L use level. Avoid contact with eyes when handling concentrate. |
| Emergency | Poisons Information Centre: 13 11 26 (24 hr, Australia) |
Composition
| Component | Amount | CAS | Hazard |
|---|---|---|---|
| Peptone from Casein | 20.0 g/L | 91079-38-8 | Not hazardous |
| Lactose | 5.0 g/L | 63-42-3 | Not hazardous |
| Sodium Chloride | 5.0 g/L | 7647-14-5 | Not hazardous |
| Salicin | 0.5 g/L | 138-52-3 | Not hazardous at use level |
| Triton X-100 | 1.0 mL/L | 9002-93-1 | Eye Irrit. 2 (H319) at high conc.; not classified at 1 mL/L use level |
| PPE | Safety glasses; nitrile gloves; lab coat |
| Eyes | Irrigate with water ≥15 min if Triton X-100 concentrate contacts eyes |
| Waste | Autoclave inoculated tubes (121°C / 15 min) before disposal as biological waste |
| Transport | Not dangerous goods — ADG, IMDG, IATA |
| Regulatory | Australian WHS Regulations 2023 | GHS 7th Edition | AICIS compliant |
Quality Specifications
| Parameter | Specification | Method |
|---|---|---|
| Appearance (powder) | Light beige, free-flowing, homogeneous | Visual |
| Appearance (prepared) | Clear to slightly opalescent, yellowish | Visual |
| pH (prepared, 25°C) | 6.9 ± 0.2 | pH meter |
| Gas production — E. coli (ATCC 25922) | Gas in Durham tube / 35°C / 24–48h | MPN inoculation test |
| Gas production — E. coli at 44.5°C | Gas in Durham tube / 44.5°C / 24h | Faecal coliform test |
| Inhibition — Enterococcus faecalis (ATCC 29212) | No gas (Gram-positive suppression by Triton X-100) | Selectivity test |
| Batch COA | Available every lot | On request |
Manufactured by AuSaMicS Pty Ltd | 31 Longview CT, Thomastown VIC 3074 | ABN 56 676 640 467
✓ Formulated per Merck 1.01699 / ISO 9308-2 specification
✓ Batch QC: pH + gas production + selectivity test per lot
✓ COA, TDS, SDS included with every order
✓ Australian stock — same-week dispatch
✓ Formulated per Merck 1.01699 / ISO 9308-2 specification
✓ Batch QC: pH + gas production + selectivity test per lot
✓ COA, TDS, SDS included with every order
✓ Australian stock — same-week dispatch
⚠️ For laboratory and environmental testing use only. Not for food, therapeutic, or direct human use.