XLT4 Agar for Enumeration of Bacteria, 500 g, Acumedia 7157A

Acumedia® XLT4 Agar for Enumeration of Bacteria, 500 g, 7157A

Features:

• XLT4 Agar is used with Tergitol 4 for isolation of non-typhi Salmonella spp and is not intended for use in diagnosis of disease or other conditions in humans
• Selective differential isolation medium for specific detection of Salmonella spp. from environmental and food samples
• Due to its highly selective nature, XLT4 Agar is particularly effective when used with samples where overgrowth of contaminating flora is expected, for example, fecally contaminated agricultural samples
• Developed to perform as per Miller & Tate in 1990, this medium was found to improve recovery of non-typhi Salmonella from chicken and farm environmental samples
• Dusch and Altwegg further established application of XLT4 Agar to salmonellae detection in clinical samples, with notable exceptions of Salmonella typhi and Salmonella paratyphi
• Presence of peptone and yeast extract provides sufficient nutrients to allow optimal growth of Salmonella spp.
• Selectivity is provided by anionic surfactant Niaproof® 4 (formerly known as Tergitol-4 / sodium tetradecylsulfate) — compound acts as effective selective agent which is active against Grampositive and many Gram-negative organisms, including Proteus spp.
• Differentiation is based on fermentation of sugars xylose, lactose and sucrose in addition to decarboxylation of lysine
• Inclusion of pH indicator, phenol red, provides visual evidence of pH decrease (yellow) or increase (red) in medium
• Ammonium iron (III) citrate is present to distinguish hydrogen-sulfide (H2S) producing from non-H2S producing organisms
• Most enteric organisms, except Shigella, will ferment xylose to produce acid
• However, salmonellae will also decarboxylate lysine to keep  pH neutral to alkali, thus maintaining red coloration
• At near neutral pH, Salmonella can produce H₂S from reduction of ammonium iron (III) citrate and thiosulphate ions producing black or black-centered colonies
• Non H₂S-producing salmonellae will be red without black center
• Other Enterobacteriaceae (non-salmonellae) which are not inhibited by Niaproof-4, will ferment xylose, lactose and/or sucrose but will not decarboxylate lysine — this fermentation activity causes decrease in pH, resulting in color change within colonies from red to yellow
• Appearance: beige pink powder
• pH: 7.2-7.6
• Flammability (gas, solid): non-flammable
• Solubility: soluble in water