Thermo Scientific™ Bismuth Sulphite Agar (Modified Wilson & Blair Medium) (Dehydrated)

Description

Isolate Salmonella typhi and other salmonllae from pathological material, sewage water supplies, food and other products with Thermo Scientific™ Oxoid™ Bismuth Sulphite Agar (Modified Wilson & Blair Medium) (Dehydrated). Bismuth Sulphite Agar is a modification of the original Wilson and Blair¹ Medium and is particularly useful for the isolation of lactose-fermenting salmonellae. The presence of bismuth sulphite and brilliant green make this medium highly selective for salmonellae.

Salmonella infection (salmonellosis) is a common bacterial disease that affects the intestinal tract. Salmonella bacteria typically live in animal and human intestines and are shed through feces. Humans become infected most frequently through contaminated water or food.

Bismuth Sulphite Agar is a selective medium for the isolation and preliminary identification of Salmonella typhi and other salmonellae from pathological material, sewage, water supplies, food and other products suspected of containing these pathogens.

• Selective: bismuth sulphite together with brilliant green acts as a selective agent making the medium selective for salmonellae while suppressing the growth of coliforms.
• Easy-to-read: Salmonellae typically grow as black colonies with a surrounding metallic sheen resulting from hydrogen sulphide production and reduction of sulphite to black ferric sulphide.

Atypical colonies may appear if the medium is heavily inoculated with organic matter. Such a situation may be prevented by suspending the sample in sterile saline and using the supernatant for inoculation.

The freshly prepared medium has a strong inhibitory action² and is suitable for heavily contaminated samples. Storing the poured plates at 4°C for 3 days causes the medium to change color to green, making it less selective with small numbers of salmonellae being recovered³. However, for Salmonella typhi recovery the latter technique is not recommended ⁴.

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