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You are here:Home » Culture Media » Media-Microbiological » XLD Agar (Powder)

XLD Agar (Powder)


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USP medium for screening material for presence or absence of Salmonella. Selective and differential medium for the isolation, cultivation and differentiation of enteric bacteria, particularly Shigella sp. from both clinical and non-clinical specimens.
Catalog #X1040
Modification of medium developed by Taylor XLD Agar has been shown to be superior to other selective media for the isolation of Shigella. Sodium deoxycholate inhibits Gram positive organisms. Xylose is fermented slowly by Shigella and Providencia and thus demonstrate an alkaline reaction (red colonies). Salmonella ferment xylose rapidly but also decarboxylate lysine giving an alkaline reaction. Excess lactose and sucrose prevent lysine positive organisms from reverting to the alkaline reaction. H2S production by Salmonella and Arizona is indicated by black centered red colonies. Sodium thiosulfate is added as the sulfur source and ferric ammonium citrate as indicator. Phenol red is used as an acid-base indicator with lactose and sucrose fermentation giving yellow colonies (acid reaction).
AppearanceLight pinkish-beige, homogeneous, free flowing powder
SolubiliityBright red - reddish orange and clear to trace hazy.
Important NoteThis product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications without the expressed written authorization of United States Biological.

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