XLD Agar – A Selective, Differential, And Indicator Medium


XLD Agar stands for Xylose Lysine Deoxycholate Agar. It was developed by Taylor. It is a selective, differential, and indicator medium for enteric pathogen isolation. It also promotes the growth of more virulent enteric organisms. It was specifically designed to isolate Shigella species and is a proven medium for the isolation of this organism from stool samples. Along with Shigella, it has also been discovered to be an excellent medium for the isolation of Salmonella species.

It differentiates between pathogenic and non-pathogenic lactose fermenter strains. Furthermore, the medium is also used to increase the frequency of growth of more fastidious pathogens, which have previously failed to grow in other formulations due to the inclusion of excessively toxic inhibitors.


A number of clinical evaluations have supported the claim that XLD Agar has relatively high efficiency in the primary isolation of Shigella and Salmonella. XLD Agar is recommended for testing foods, dairy products, and water and is included in the USP microbial limit test for screening specimens for the presence or absence of Salmonella.

On XLD agar, Salmonella typhi produces red colonies with a black center, while Salmonella paratyphi produces only red colonies with no black center, and Salmonella choleraesuis produces red colonies. Shigella sonnei and Shigella flexneri produce red colonies; Escherichia coli forms large, flat, yellow colonies, and some strains of Escherichia coli are inhibited; Proteus vulgaris forms yellow colonies; Enterobacter or Klebsiella forms mucoid, yellow colonies; and Pseudomonas aeruginosa forms pink, flat, rough colonies.

Composition of XLD Agar

Ingredients

Gms/Ltr

Yeast extract

3.000

L-Lysine

5.000

Lactose

7.500

Xylose

3.500

Sodium chloride

5.000

Sodium deoxycholate

2.500

Sodium thiosulphate

6.800

Ferric ammonium citrate

0.800

Phenol red

0.080

Agar

15.000

TM Media - Manufacturer of Ready-to-Use XLD Agar Plates

TM Media is a well-known manufacturer of microbiology essentials. They offer a wide range of Culture Media, Biological Media Bases, Lab Chemicals, Lab Consumables, and much more. Their Culture Media and Biological Media Bases both are available in animal and non-animal origin. Culture Media is available at TM Media in two forms: Dehydrated and Ready-to-Use.

TM Media’s XLD Agar Plates are a perfect choice for Clinical Testing. These 90-mm plates are easy to use and give accurate results.

For more, visit www.tmmedia.in.

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