BISMUTH SULPHITE AGAR (VEG.)

Description

This medium is prepared by using Veg special peptone and Veg extract which is free of BSE/TSE risks. Bismuth Sulphite Agar is the modification of Wilson and Blair formula, which is recommended by various Associations for the isolation and preliminary identification of Salmonella serotype Typhi and other Salmonellae from pathological materials, sewage, water, food and other products. Present medium is the modification of Bismuth Sulphite Agar where all animal based peptones are replaced with Veg peptones. Bismuth Sulphite Agar was stable, sensitive and found to be superior to Wilson?s original medium. Brilliant green and bismuth sulphite incorporated into the medium inhibit the intestinal gram-negative and gram-positive bacteria. Salmonella serotype Typhi, Salmonella serotype Enteritidis and Salmonella serotype Typhimurium typically grow as black colonies with a surrounding metallic sheen resulting from hydrogen sulfide (H2S) production and reduction of sulphite to black ferric sulphide. Salmonella serotype Paratyphi A grow as light green colonies. Also this medium favours use of larger inoculum as compared to other selective media, as it has unique inhibitory action towards gram-positive and coliform organisms. The medium may be inhibitory to some strains of Salmonella species and therefore should not be used as the sole selective medium for these organisms. Shigella species are mostly inhibited on this medium and also some Salmonellae like Salmonella serotype Sendai, Salmonella serotype Berta, Salmonella serotype Gallinarum, Salmonella serotype Abortus-equi are inhibited. Colonies on Bismuth Sulphite Veg Agar may be contaminated with other viable organisms; therefore, isolated colonies should be subcultured on to a less selective medium.