EMB Agar (250g) - Levine's Eosin-Methylene Blue Lactose Agar for isolating intestinal pathogens and E. coli

Levine’s Eosin-Methylene Blue Lactose Agar (EMB Agar)

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Levine’s Eosin-Methylene Blue Lactose Agar (EMB Agar) is a selective and differential solid culture medium used for the isolation and differentiation of enteric pathogenic bacteria, particularly coliforms and Escherichia coli.

The combination of eosin Y and methylene blue dyes inhibits most Gram-positive organisms, while lactose fermentation allows differentiation of coliform bacteria based on colony color and appearance. Strong lactose fermenters such as E. coli typically produce dark colonies with a metallic green sheen, whereas non-fermenters remain colorless or pale.

⚠ For laboratory research and quality control use only. Not intended for clinical diagnostic or therapeutic use.

🔬 Intended Use

  • Selective isolation of enteric pathogenic bacteria

  • Differentiation and enumeration of coliforms

  • Detection and identification of Escherichia coli

  • Food, water, and pharmaceutical microbiology testing

📦 Product Specifications

  • Product Name: Levine’s Eosin-Methylene Blue Lactose Agar

  • Common Name: EMB Agar

  • Physical Form: Dehydrated powder

  • Package Size: 250 g / bottle

  • Storage Condition: Room temperature, dry place

  • Shelf Life: 3 years

🧬 Medium Composition (per liter)

  • Pancreatic Digest of Gelatin ………………… 10.0 g
  • Dibasic Potassium Phosphate ……………… 2.0 g
  • Lactose …………………………………………….. 10.0 g
  • Eosin Y ……………………………………………… 0.4 g
  • Methylene Blue ………………………………….. 0.065 g
  • Agar …………………………………………………… 15.0 g
  • Final pH: 7.1 ± 0.2 (at 25 °C)

⚗️ Preparation Instructions

  1. Suspend 37.5 g of dehydrated medium in 1,000 ml of distilled or deionized water
  2. Heat to boiling for 1 minute with frequent stirring until completely dissolved
  3. Dispense into suitable containers
  4. Sterilize by autoclaving at 121 °C for 15 minutes
  5. Cool to approximately 55 °C
  6. Pour into sterile Petri dishes
  7. Allow to solidify and store plates for use

🧫 Storage & Stability

  • Store dehydrated medium at room temperature, protected from moisture and light
  • Do not use medium showing caking, discoloration, or dye degradation
  • Prepared plates should be used promptly or stored refrigerated and protected from light

⚠️ Limitations & Precautions

  • Dyes are light-sensitive; avoid prolonged exposure to light
  • Overheating may reduce selectivity
  • Colony morphology should be confirmed with additional biochemical tests

Quality Control Examples

1. Physicochemical Analysis

Test ItemStandardTest Result
Powder AppearancePurple-red powder, uniform, no impuritiesPurple-red powder, uniform, no impurities
Solution/ColloidDark red, transparent, no impuritiesDark red, transparent, no impurities
Gel Strength450～550 g/cm²550 g/cm²
pH (25℃)7.1 ± 0.27.28
Moisture≤ 5%4.5%

2. Sensitivity Test (Incubated at 25℃)Standard: Growth Rate ≥ 70%

Standard: Growth Rate ≥ 70%

QC StrainGrowth Rate & CharacteristicsConclusion
Escherichia coli
CMCC(B) 44102		92%, Colonies with metallic sheenConforms
Escherichia coli
ATCC 25922		91%, Colonies with metallic sheenConforms
Enterobacter aerogenes
ATCC 13048		89%, Pink coloniesConforms
Enterobacter cloacae
ATCC 13047		90%, Pink coloniesConforms
Staphylococcus aureus
CMCC(B) 26003		No growth (Inhibition)Conforms

Conclusion:The product has passed both physicochemical and sensitivity tests. The inhibitory effect is satisfactory, and colony characteristics are typical.Overall Result: Conforms / Pass

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