Lysine Decarboxylase Broth (LDB) | Enterobacteriaceae Detection – Ausamics

$45.00 AUD

AuSaMicS Life Science • Biochemical Identification Media

Lysine Decarboxylase Broth

Differential Broth for Lysine Decarboxylase Activity

Standard liquid medium for determining whether a microorganism possesses lysine decarboxylase, enabling conversion of L-lysine to cadaverine under anaerobic conditions. Widely used in Salmonella confirmation, Enterobacteriaceae differentiation, and conventional biochemical identification workflows.

AS-1278 🧪 Biochemical Identification ✓ Salmonella Workflow 🔬 Decarboxylase Test

Readout: Yellow to purple reversal Requirement: Mineral oil overlay Use: Enterobacteriaceae differentiation

Biochemical Media Specialist

Salmonella Confirmation - Classical lysine-positive screening support

Viability Control - Initial glucose fermentation step

Clear Indicator System - Bromocresol purple colour shift

Anaerobic Reaction Design - Mineral oil overlay method

Routine Lab Utility - Conventional identification series

Classical Decarboxylase Test

Essential for enteric identification workflows

🧪 Complete Formulation & Reaction Principle

📋 Composition (per Liter)

Ingredient	Concentration	Primary Function	Contribution
L-Lysine HCl	5.0 g	Target substrate	Provides lysine for decarboxylase reaction
Yeast Extract	3.0 g	Growth support	Provides nitrogen, vitamins, and growth factors
Glucose	1.0 g	Fermentable carbohydrate	Initial acidification confirms viability
Bromocresol Purple	0.02 g	pH indicator	Yellow in acid, purple in alkaline reaction

Final pH: 6.8 ± 0.2 at 25°C

⚗️ Principle of the Test

Viability Check
Small amount of glucose is fermented first, turning the broth yellow

Anaerobic Decarboxylation
Mineral oil overlay creates conditions required for lysine decarboxylase activity

Alkaline Reversal
Positive organisms convert lysine to cadaverine, returning the broth to purple

Why Lysine Decarboxylase Broth? It helps distinguish key enteric pathogens and coliforms in classical biochemical identification, especially in Salmonella workups.

Complete Enteric Identification Media Portfolio

Medium	Type	Main Readout	Best Application	Workflow Position	Key Advantage
Lysine Decarboxylase Broth	Biochemical differential broth	Yellow to purple reversal	Salmonella confirmation and enteric differentiation	After primary isolation / screening	Classical lysine decarboxylase determination
Triple Sugar Iron Agar	Differential tube medium	Sugar use, gas, H₂S	Primary enteric screening	Early screening step	Multiple reactions in one tube
Kligler Iron Agar	Differential tube medium	Glucose/lactose fermentation and H₂S	Preliminary enteric differentiation	Initial workup	Classic enteric separation tool
Urea Broth / Urea Agar	Biochemical reaction medium	Urease activity	Differentiation of urease-positive enterics	Supplementary test	Rapid enzyme-based interpretation
Citrate Agar	Utilization medium	Alkaline citrate utilization	IMViC and enteric ID	Supplementary biochemical step	Common companion test in enteric profiles

Strategic Medium Selection for Lysine Decarboxylase Testing

✅ Lysine Decarboxylase Broth Advantages

✓ Classical Salmonella Support: Useful in standard confirmation workflows
✓ Built-in Viability Check: Initial glucose acidification confirms growth
✓ Clear Colour Logic: Purple reversal indicates positive decarboxylation
✓ Widely Recognised: Used in conventional and regulatory identification series
✓ Good Differential Utility: Helps separate Salmonella/Citrobacter from many other enterics

⚠️ Method Considerations

▲ Anaerobic Condition Required: Mineral oil or paraffin overlay is essential
▲ Heat Sensitivity: Over-sterilization can affect lysine performance
▲ Interpretation Timing Matters: Early and late reads can differ
▲ Variable Organisms Exist: Some Proteus / Providencia reactions may be atypical or fading

🎯 Best-Fit Applications

◆ Salmonella Confirmation: Follow-up after TSI/KIA screening
◆ Citrobacter Differentiation: Support in separating coliform groups
◆ API / Conventional ID Workflows: Enteric biochemical profiling
◆ Reference Laboratory Testing: Regulatory and classical microbiology methods

📊 Interpretation Guide

Observation	Interpretation	Typical Meaning	Examples
Initial yellow, then purple	Lysine decarboxylase positive	Viability confirmed, decarboxylation occurred	Salmonella, many Citrobacter
Remains yellow	Lysine decarboxylase negative	Glucose fermentation without alkaline reversal	E. coli, Shigella, Klebsiella, Enterobacter
Fading / colourless / variable	Variable or atypical	Interpret with caution and companion tests	Proteus, some Providencia

🔬 Quality Control & Performance Guidance

Typical Positives:
Salmonella (non-typhi), many Citrobacter
some Providencia

Typical Negatives:
E. coli, Shigella, Klebsiella
Enterobacter, Serratia

Incubation:
35–37°C
18–48 h after overlay

Preparation Note:
Sterilize only 10–12 min
Lysine is heat-sensitive

Positioning: A core biochemical broth for laboratory identification of enteric bacteria, especially useful in Salmonella confirmation and classical regulatory microbiology workflows.

📋 Technical Specifications

Catalogue Number	AS-1278
Medium Type	Differential biochemical broth
Base Weight	9.02 g/L
Final pH	6.8 ± 0.2 (at 25°C)
Indicator	Bromocresol Purple
Anaerobic Requirement	Mineral oil or liquid paraffin overlay
Dispensing Volume	4–5 mL per tube
Sterilization	121°C for only 10–12 minutes
Incubation	35–37°C for 18–48 h
Prepared Tube Storage	2–8°C, protected from light, up to 3 months

🧫 Primary Applications

✓ Confirmation of Salmonella after TSI/KIA screening
✓ Differentiation of Citrobacter from other coliforms
✓ Conventional biochemical identification series
✓ Support for API-style and regulatory workflows

⚗️ Preparation & Test Procedure

1. Dissolve 9.02 g dehydrated medium in 1 L purified water.
2. Dispense 4–5 mL into small tubes.
3. Autoclave at 121°C for only 10–12 minutes.
4. Inoculate heavily from an 18–24 h pure culture.
5. Overlay with 8–10 mm sterile mineral oil or liquid paraffin and incubate at 35–37°C for 18–48 h.

📦 Storage & Intended Use

Prepared tubes: Store at 2–8°C, protected from light.

Use period: Use within 3 months for optimal performance.

Test note: Read results in the context of proper overlay and incubation timing.

Notice: For laboratory identification use only.

AuSaMicS Life Science: Professional microbiology media for biochemical identification, food safety, clinical and industrial microbiology, research, and routine laboratory workflows. Product information is provided for laboratory and technical evaluation purposes only.