Thermo Scientific™ Salmonella Shigella/XLD Biplate

Description

• Perform selective and differential isolation of enteric gram-negative bacilli, especially Salmonella and Shigella , from clinical specimens using Thermo Scientific™ Remel™ Salmonella Shigella(SS)/XLD Biplate
• This biplate is used for isolating bacteria such as Salmonella and Shigella spp 1-3
• Leifson modified the Desoxycholate-Citrate Agar used for the detection of enteric pathogens 4 and added bile salts mixture to inhibit the growth of gram-positive organisms
• XLD medium was developed by Taylor 5
• Salmonella and Shigella are major causes of bacterial enteric illness with transmission occurring via the fecal-oral route, person-to-person contact, or by the ingestion of contaminated food or water
• Ready-to-use – Convenience of a prepared media
• Performs screening and isolation on the same dish using two agars
• Ease of handling and less product is used
• Ease of identification – On SS agar colonies of Salmonella and Shigella are smooth and opaque; some appear to have black centered colonies whereas on XLD agar Salmonella produces red colonies without black center and Shigella colonies are transparent
• Selective – Due to the inclusion of selective inhibitory substances brilliant green, bile salts, thiosulphate, and citrate in SS agar and desoxycholate in XLD agar, most gram-positive and coliform organisms are inhibited
• The SS agar contains bile salts, brilliant green and citrates which acts as selective agents and inhibit gram-positive bacteria and coliforms
• Sodium thiosulfate, a sulfur source and ferric ammonium citrate work as an indicator to enable organisms which produce H 2 S to form black-centered colonies, including some strains of Salmonella
• Lactose is a differentiator
• The XLD agar contains desoxycholate which acts as a selective agent and inhibits gram-positive organisms
• Xylose is fermented by most gram-negative bacilli
• Lysine acts as a differentiator for Salmonella spp
• from non-pathogenic enteric bacilli
• Salmonella produces lysine decarboxylase which causes pH to revert to alkaline after xylose is fermented, producing red colonies
• Lactose and sucrose are added in excess to prevent lysine-positive coliforms from reverting to alkaline conditions
• Sodium thiosulfate, a sulfur source, and ferric ammonium citrate work as indicators to enable organisms which produce H 2 S to form black-centered colonies under alkaline conditions
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• Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.