KM0013 – Xylose Lysine Desoxycholate Agar (XLD)

//KM0013 – Xylose Lysine Desoxycholate Agar (XLD)

KM0013 – Xylose Lysine Desoxycholate Agar (XLD)

Xylose Lysine Deoxycholate (XLD) agar is used for the isolation and detection of Salmonella and Shigella spp.
Developed by Taylor, xylose lysine agar base was used for isolating and differentiating Gram-negative enteric bacilli. The addition of sodium thiosulfate, ferric ammonium citrate, and sodium deoxycholate created the more selective medium, XLD agar. This medium was found to be satisfactory for the isolation of Shigella and Providencia spp., as well as proving to be an effective differential media.
The yeast extract is the source of the required nitrogen, carbon and vitamins. Lactose, sucrose and xylose are fermentable carbohydrates. Sodium deoxycholate, sodium thiosulphate and ferric ammonium citrate are selective agents. Phenol red acts as a pH indicator. Sodium chloride maintains the osmotic balance.
Most enteric bacteria including Salmonella spp., can ferment xylose to produce acid. Shigella spp. are unable to do this and thus the colonies remain red. Once xylose has been completely utilized Salmonella spp. will decarboxylate lysine resulting in a pH increase to alkaline. Salmonella and Shigella spp. are differentiated as Salmonellae spp. are able to metabolise thiosulphate producing hydrogen sulphide resulting in colonies with black centres.
Stool specimens or rectal swabs may be plated directly onto XLD agar. Selective enrichment broths, such as Selenite Broth or Tetrathionate Broth, may be used prior to streaking. For specific procedures refer to appropriate references.

 

SKU: KM0013 Category:

Additional Information

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Storage Temp (°C)

Dehydrated Medium Appearance

Prepared Medium Appearance

Dehydrated Medium Colour

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Dehydrated PH

Prepared PH

Product Description

Organisms Ref. No Result
Salmonella typhimurium NCTC 12023 Growth, translucent colonies with black centre
Salmonella enteritidis ATCC 13076 Growth, translucent colonies with black centre
Shigella flexneri ATCC 12022 Growth, red colonies
Escherichia coli NCTC 12241 Inhibited
Enterococcus faecalis NCTC 12697 Inhibited

 

Formula*

g/L
Yeast extract 3.0
Lactose 7.5
Lysine 5.0
Sucrose 7.5
Xylose 3.75
Sodium chloride 5.0
Phenol red 0.08
Sodium deoxycholate 1.0
Sodium thiosulphate 6.8
Ferric ammonium citrate 0.8
Agar 13.0
Total 53.0
*Adjusted/supplemented as required to meet performance requirements

Preparation

Suspend 53g of the medium in one litre of deionised / purified water. Allow the medium to soak whilst mixing for 10 minutes. Heat with frequent agitation and boil for one minute to completely dissolve the medium. DO NOT AUTOCLAVE this medium. Cool to 45-50°C and aseptically dispense into appropriate sterile containers.