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EMB Broth | Eosin Methylene Blue Medium for Coliform Detection | AS‑1229
$35.00 AUD
AuSaMicS Life Science • Selective & Differential Culture Media
EMB Broth
Eosin Methylene Blue Broth
Classic selective and differential liquid medium for detection and differentiation of gram-negative enteric bacteria. Eosin Y and methylene blue dyes deliver powerful gram-positive suppression and distinctive colour responses — a cornerstone of water, food, and pharmaceutical microbiology.
Cat #: AS-1229
APHA / ISO Compliant
✓ Australian Stock
🟣 Dual-Dye Selectivity
🚀 Same-Day Dispatch: Australian Stock
🧫 Selective & Differential: Gram-negative enteric ID
🌡️ 35–37°C Incubation: 24–48 hours
🏆 Enteric Detection Specialist
🟣 Dual-Dye System — Eosin Y + Methylene Blue
🔬 Selective & Differential — Single medium, dual function
📋 Complete Package — COA + SDS included
⚡ Fast Supply — Ships within 24h
📞 Expert Support — Protocol optimization
Levine Formulation
Lactose + sucrose dual-sugar for broader coliform differentiation
🔬 Technical Overview & Biochemistry
EMB Broth is a classic selective and differential liquid medium widely used for the detection, isolation, and preliminary differentiation of gram-negative enteric bacteria — particularly coliforms and E. coli — in water, food, environmental, and pharmaceutical samples.
Dual-Dye Selectivity & Differential Mechanism:
Eosin Y — Anionic dye; inhibits gram-positive organisms by interfering with cell wall integrity; forms coloured complexes with acid end-products of fermentation
Methylene Blue — Acts synergistically with Eosin Y for gram-positive inhibition; enhances differential colour contrast between fermenters and non-fermenters
Lactose & Sucrose (Levine formulation) — Fermentable carbohydrates; rapid acid producers (e.g., E. coli) yield turbidity with purplish-black precipitate; slow fermenters and non-fermenters remain clear or lightly turbid
Eosin Y — Anionic dye; inhibits gram-positive organisms by interfering with cell wall integrity; forms coloured complexes with acid end-products of fermentation
Methylene Blue — Acts synergistically with Eosin Y for gram-positive inhibition; enhances differential colour contrast between fermenters and non-fermenters
Lactose & Sucrose (Levine formulation) — Fermentable carbohydrates; rapid acid producers (e.g., E. coli) yield turbidity with purplish-black precipitate; slow fermenters and non-fermenters remain clear or lightly turbid
Result Interpretation: Turbid growth with dark purple/black precipitate = strong acid producer (typical E. coli). Turbid without precipitate = coliform / gram-negative. Clear = inhibited or no growth (gram-positive suppressed).
⚙️ Mode of Action
Eosin Y and methylene blue form a complex at low pH that precipitates within colonies or broth producing acid from lactose/sucrose fermentation. Gram-positive organisms are inhibited because the dyes disrupt their cell membrane at the concentrations used, preventing growth. Gram-negative enteric bacteria tolerate the dye system and grow freely — with rapid acid producers such as E. coli generating sufficient pH drop to trigger a visible dark precipitate, while non-fermenting gram-negatives remain undifferentiated by turbidity alone.
📊 Gram-Negative Enteric Media Comparison
🧬 Applications
💧 Water Quality Testing
Detection and presumptive differentiation of coliform bacteria in potable, recreational, and environmental water samples — supports MPN multi-tube methodology.
🍽️ Food Microbiology
Enrichment and selective detection of gram-negative enteric contaminants in food products, food processing surfaces, and ingredients — dairy, meat, produce, and ready-to-eat foods.
💊 Pharmaceutical QC
Non-sterile product bioburden testing and E. coli absence tests per USP <61>, BP, and TGA requirements — liquid medium format suits enrichment steps.
🏭 Industrial Microbiology
Process water, cooling water, and environmental monitoring in manufacturing environments where gram-negative enteric control is critical.
Additional Laboratory Applications:
- Clinical Microbiology: Selective enrichment prior to plating on differential agar
- Research: Coliform ecology, antibiotic resistance, and E. coli population studies
- Teaching Labs: Classical gram-negative differentiation demonstrations
- Veterinary Diagnostics: Enteric pathogen detection in animal samples
- Environmental Monitoring: Soil leachate and irrigation water assessment
- NATA Accredited Labs: Routine coliform testing workflows
📋 Recommended Procedure
1️⃣
Prepare Medium
Dissolve 20.0 g/L in purified water. Mix well. Dispense into tubes with Durham tubes if gas detection required.
2️⃣
Sterilise
Autoclave at 121°C for 15 min. Allow to cool to room temperature before inoculation.
3️⃣
Inoculate
Add sample (water, food homogenate, or swab rinse). Use 1:10 ratio for food samples.
4️⃣
Incubate
35–37°C for 24–48 h. Examine at 24 h and again at 48 h if negative.
5️⃣
Interpret & Subculture
Turbid with dark precipitate = positive. Subculture to EMB Agar or confirmatory media for full identification.
💡 Tip: For MPN water testing, use triple-strength EMB Broth in the first dilution tube (1 mL sample into 5 mL triple-strength broth) to avoid dilution of selectivity. Pair with EMB Agar for definitive colony morphology confirmation.
💡 Protocol Optimization Guidelines
Preparation:
Dissolve 20.0 g/L in purified water. Autoclave 121°C / 15 min. Avoid overheating — excessive heat darkens the medium and reduces selectivity.
Dissolve 20.0 g/L in purified water. Autoclave 121°C / 15 min. Avoid overheating — excessive heat darkens the medium and reduces selectivity.
pH (25°C):
7.1 ± 0.2 after sterilisation
7.1 ± 0.2 after sterilisation
Triple-Strength Variant:
Dissolve 60.0 g/L for use in first-tube MPN series when inoculating large sample volumes (≥1 mL).
Dissolve 60.0 g/L for use in first-tube MPN series when inoculating large sample volumes (≥1 mL).
Storage (prepared):
2–8°C, use within 2 weeks. Protect from light — dyes are photosensitive. Dehydrated powder: below 25°C, dry and dark.
2–8°C, use within 2 weeks. Protect from light — dyes are photosensitive. Dehydrated powder: below 25°C, dry and dark.
📋 Technical Specifications
| Catalogue Number | AS-1229 |
| Full Name | Eosin Methylene Blue Broth (Levine) |
| Format | Dehydrated powder |
| Reconstitution | 20.0 g/L in purified water |
| pH (25°C) | 7.1 ± 0.2 |
| Incubation Temp | 35–37°C |
| Incubation Time | 24–48 hours |
| Positive Result | Turbid + dark purple-black precipitate |
| Negative Result | Clear / no turbidity |
| Selective Agents | Eosin Y, Methylene Blue |
| Sterilisation | Autoclave 121°C / 15 min |
| Formulation Type | Levine (lactose + sucrose) |
| HS Code | 3821.00.00 |
✅ Quality Control Performance
| Test Organism | ATCC | Expected Result | CFU Spec |
|---|---|---|---|
| Escherichia coli | 25922 | Turbid + dark precipitate | ≤100 CFU |
| Klebsiella pneumoniae | 13883 | Turbid growth | ≤100 CFU |
| Enterococcus faecalis | 19433 | Inhibited / no growth | ≤100 CFU |
| Staphylococcus aureus | 25923 | Inhibited / no growth | ≤100 CFU |
🧪 Typical Formulation (per litre)
| Peptone | 10.0 g |
| Lactose | 5.0 g |
| Sucrose | 5.0 g |
| Dipotassium Hydrogen Phosphate | 2.0 g |
| Eosin Y | 0.4 g |
| Methylene Blue | 0.065 g |
* Levine formulation (dual-sugar). Formulation may vary slightly between lot numbers. Refer to the current COA for exact composition.
📜 Standards & Regulatory Compliance
- ✓ APHA Standard Methods — Coliform detection MPN methodology
- ✓ ISO 9308-2 — Water quality, MPN method for E. coli and coliforms
- ✓ USP <61> / <62> — Pharmaceutical microbial enumeration and absence tests
- ✓ TGA / BP — British Pharmacopoeia and TGA non-sterile product testing
- ✓ ISO 21528 — Horizontal methods for detection of Enterobacteriaceae
- ✓ NATA Accreditation — Suitable for NATA-accredited laboratories
📝 Alternative Names
EMB Broth
Eosin Methylene Blue Broth
Levine EMB Broth
Eosin-Methylene Blue Liquid Medium
EMB Liquid Medium (Levine formulation)
Gram-Negative Selective Broth
🔄 Cross-Reference / Equivalent Products
Cross-references are provided for convenience. Catalogue numbers are trademarks of their respective owners. AuSaMicS products are manufactured and quality-tested independently.
🧬 Complete Gram-Negative Enteric Detection System
Selective & Differential Media
Water Testing & Membrane Filtration Media
Need Coliform Detection Method Support?
Our microbiologists can assist with MPN workflow design, USP <61> pharmaceutical testing setup, APHA water testing methods, and NATA compliance documentation.
For laboratory, research, and industrial use only. Not for food, feed, household, cosmetic, therapeutic, or personal use. Results should be interpreted by qualified laboratory personnel in accordance with applicable standard methods.
AuSaMicS Pty Ltd | ABN: 56 676 640 467 | 31 Longview CT, Thomastown VIC 3074, Australia
www.ausamics.com.au | support@ausamics.com.au | +61 412 520 598
Same-day dispatch • Australian stock • Full documentation included