XLD (XYLOSE LYSINE DEOXYCHOLATE) AGAR

General description

GranuCult^® Xylose Lysine Deoxycholate agar is designed for the isolation and differentiation of pathogenic Enterobacteriaceae, especially of Shigella and Salmonella species. Degradation of xylose, lactose, and sucrose to acid causes phenol red to change its color to yellow. Production of hydrogen sulfide is indicated by thiosulfate and iron (III) salt, which react to form a precipitate of black iron sulfide in the colonies. Bacteria that decarboxylate lysine to cadaverine can be recognized by the appearance of a purple coloration around the colonies due to an increase in pH. These reactions can proceed simultaneously or successively, causing the pH indicator to exhibit various shades of color, or it may change its color from yellow to red on prolonged incubation. The culture medium is moderately selective, thus the growth of unwanted organisms is suppressed, while sought bacteria can be tentatively grouped by reading the net effect of carbohydrate dissimilation, lysine decarboxylation, and the formation of hydrogen sulfide leading to black colonies. Agar is the solidifying agent.

Application

GranuCult^® Xylose Lysine Deoxycholate agar is suitable for the isolation and differentiation of pathogenic Enterobacteriaceae, especially of Shigella and Salmonella species from food and animal feed, water, and other materials.

Analysis Note

Appearance (clearness): clear to slightly opalescent
Appearance (colour): red
pH-value (25 °C): 7.2 - 7.6
Growth promotion test in accordance with the current version of DIN EN ISO 11133.

Inoculum on reference medium (Salmonella typhimurium ATCC 14028 (WDCM 00031)):
Inoculum on reference medium (Salmonella enteritidis ATCC 13076 (WDCM 00030)):
Colony count (Salmonella typhimurium ATCC 14028 (WDCM 00031)):
Colony count (Salmonella enteritidis ATCC 13076 (WDCM 00030)):
Recovery on test medium (Salmonella typhimurium ATCC 14028 (WDCM 00031)): ≥ 50 %
Recovery on test medium (Salmonella enteritidis ATCC 13076 (WDCM 00030)): ≥ 50 %
Growth (Escherichia coli ATCC 25922 (WDCM 00013)): Growth or partial inhibition
Growth (Escherichia coli ATCC 8739 (WDCM 00012)): Growth or partial inhibition
Growth (Enterococcus faecalis ATCC 29212 (WDCM 00087)): total inhibition
Growth (Enterococcus faecalis ATCC 19433 (WDCM 00009)): total inhibition
Colonies (Salmonella typhimurium ATCC 14028 (WDCM 00031)): Colonies with black centre
Colonies (Salmonella enteritidis ATCC 13076 (WDCM 00030)): Colonies with black centre
Colonies (Escherichia coli ATCC 25922 (WDCM 00013)): Yellow colonies
Colonies (Escherichia coli ATCC 8739 (WDCM 00012)): Yellow colonies
Incubation: 24 ± 3 hours at 37 ± 1 °C
A recovery rate of 50 % is equivalent to a productivity value of 0.5.
The indicated colony counts result from the sum of a triple determination.
Reference media: Tryptic Soy Agar

Footnote

We offer two media types: the superior granulated GranuCult^® and the cost-efficient powdered NutriSelect^® culture media, depending on your needs.
The designations basic, plus, or prime are added to indicate the quality control level, from basic quality control to standard QC plus to prime for full regulatory compliance.

Legal Information

GRANUCULT is a registered trademark of Merck KGaA, Darmstadt, Germany

NutriSelect is a registered trademark of Merck KGaA, Darmstadt, Germany