Xylose Lysine Deoxycholate (XLD) Agar
Xylose Lysine Deoxycholate (XLD) Agar
Selective & Differential Medium for Salmonella and Shigella Isolation
Product Identification
General Information
Product Name: Xylose Lysine Deoxycholate (XLD) Agar
Catalogue Number: AS-1378
Medium Type: Selective and differential enteric culture medium
Form: Dehydrated powder
Product Overview
Xylose Lysine Deoxycholate (XLD) Agar is a selective and differential solid medium designed for the isolation and differentiation of Salmonella and Shigella species from food, environmental, and laboratory samples.
The formulation contains xylose, lactose, and sucrose to assess carbohydrate fermentation, lysine to detect decarboxylation reactions, and sodium deoxycholate to inhibit Gram-positive organisms. Phenol red serves as a pH indicator, while ferric ammonium citrate enables detection of hydrogen sulfide (H₂S) production.
XLD Agar is widely used in food microbiology, public health laboratories, and environmental monitoring, and is compatible with recognised international testing methods.
Principle of the Medium
Functional Components
Xylose, Lactose, Sucrose: Fermentable carbohydrates for differentiation
Lysine: Detects lysine decarboxylation
Sodium Deoxycholate: Selective agent inhibiting Gram-positive bacteria
Phenol Red: pH indicator for carbohydrate fermentation
Ferric Ammonium Citrate: Detects hydrogen sulfide (H₂S) production
Peptone & Yeast Extract: Provide nitrogen, vitamins, and growth factors
Typical Composition (per litre)
Formulation Information
Yeast Extract: 3.0 g
Peptone / Proteose Peptone: 10.0 g
Lactose: 7.5 g
Sucrose: 7.5 g
Xylose: 4.0 g
Sodium Chloride: 5.0 g
Sodium Deoxycholate: 0.8 g
Ferric Ammonium Citrate: 0.8 g
Phenol Red: 0.025 g
Agar: 15.0 g
Purified Water: q.s. to 1 L
Final pH: 7.4 ± 0.2 at 25 °C
Applications
Food & Environmental Microbiology
Selective isolation of Salmonella and Shigella from food and water samples
Routine food safety and public health monitoring
Laboratory & Research Use
Differentiation of enteric Gram-negative bacteria
Detection of H₂S-producing organisms
Key Features
Performance Advantages
Selective for Gram-negative enteric pathogens
Differential carbohydrate fermentation reactions
Clear identification of H₂S-producing colonies
Nutrient-rich formulation for pathogenic Enterobacteriaceae
Suitable for recognised international testing protocols
Preparation Guidelines
General Preparation
Suspend 61.55 g of dehydrated medium in 1 L of purified water
Heat with agitation until completely dissolved
Dispense into Petri dishes or slants as required
Sterilise by autoclaving at 121 °C for 15 minutes
Cool to 45–50 °C before pouring plates or preparing slants
Incubation
Recommended Conditions
Temperature: 35–37 °C
Incubation time: 18–24 hours (up to 48 hours for slow-growing organisms)
Interpretation of Results
Typical Colony Appearance
Red colonies: Shigella spp. (non-fermenters)
Yellow colonies: Lactose/xylose/sucrose fermenters
Red colonies with black centres: Salmonella spp. (H₂S production)
Colony colour and morphology assist in differentiation and enumeration.
Storage & Stability
Storage Conditions
Dehydrated medium: 15–30 °C, dry and tightly sealed
Prepared plates or slants: 2–8 °C, protected from light
Use within the recommended shelf life for optimal performance.
Intended Use & Safety
Regulatory Statement
For laboratory use only.
Not intended for human, animal, or food consumption.
Refer to the Safety Data Sheet (SDS) prior to use.