Bismuth sulfite agar

Bismuth Sulfite Agar is a type of agar used as a selective and differential medium in microbiology. It was developed by Wilson and Blair in 1927 to isolate Salmonella typhi, the bacteria responsible for typhoid fever.

Composition

Bismuth Sulfite Agar contains bismuth sulfite, beef extract, dextrose, ferric citrate, and brilliant green. The bismuth and sulfite in the medium inhibit the growth of most bacteria other than Salmonella. The brilliant green dye also helps to inhibit the growth of other bacteria, making the medium highly selective.

Uses

Bismuth Sulfite Agar is primarily used for the isolation of Salmonella species, especially Salmonella typhi. It is also used in the identification of other Enterobacteriaceae.

Procedure

A sample is streaked onto the surface of the agar and incubated at 35°C for 24 hours. If Salmonella typhi is present, it will grow as black or greenish-black colonies. Other bacteria, if they grow at all, will produce colonies of a different color.

Limitations

While Bismuth Sulfite Agar is highly selective for Salmonella typhi, it may also allow the growth of some other Salmonella species and a few other types of bacteria. Therefore, additional tests are usually required to confirm the identity of the bacteria.

Safety

Bismuth Sulfite Agar should be handled with care as it contains bismuth sulfite, which can be harmful if inhaled or swallowed.

Bismuth sulfite agar gallery

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  Agar plates