Xylose Lysine Deoxycholate (XLD) Agar was originally developed to improve the recovery of Shigella species, which are often inhibited by more aggressive selective media. It utilizes a sophisticated system of sugars (xylose, lactose, and sucrose) and amino acids (L-lysine) to differentiate organisms based on carbohydrate fermentation and decarboxylation. Sodium deoxycholate is included as a selective agent to inhibit Gram-positive bacteria. The medium also contains a hydrogen sulfide (H₂S) indicator system (sodium thiosulfate and ferric ammonium citrate), which produces black-centered colonies in H₂S-producing organisms like Salmonella. As part of the NutriSelect® Plus line, this medium undergoes rigorous quality control for reliable performance.
Advantages
- Improved Recovery: Higher recovery rates for fastidious Shigella and Salmonella strains compared to SS Agar or Hektoen Enteric Agar.
- NutriSelect® Plus Quality: Premium grade medium ensuring high batch-to-batch consistency and performance.
- Triple Differentiation: Detects xylose fermentation, lysine decarboxylation, and H₂S production in a single step.
- Clear Visual Cues: Distinctive color changes in the phenol red indicator facilitate easy screening of pathogens.
- Broad Compliance: Suitable for use following various international standards for food and clinical microbiology.
Interpretation of Results
| Microorganism |
Colony Appearance |
| Salmonella spp. |
Red colonies with black centers |
| Shigella spp. |
Red, translucent colonies |
| Escherichia coli |
Large, yellow, opaque colonies |
| Enterobacter / Klebsiella |
Mucoid, yellow colonies |
Technical specifications
| Catalogue number |
95586 |
| Brand / Product Line |
Sigma-Aldrich / NutriSelect® Plus |
| Form |
Powder |
| Typical Composition (g/L) |
Xylose (3.5); L-Lysine (5.0); Lactose (7.5); Sucrose (7.5); NaCl (5.0); Yeast extract (3.0); Sodium deoxycholate (2.5); Sodium thiosulfate (6.8); Ferric ammonium citrate (0.8); Phenol red (0.08); Agar (15.0) |
| pH (at 25 °C) |
7.4 ± 0.2 |
| Preparation |
56.68 g/L |
| Storage Temperature |
15 – 25 °C |
Available packaging options
| 95586-500G |
500 g plastic bottle |
