On which plates can you determine production of hydrogen sulfide? 1. HE 2. MSA 3. MacConkey...

On which plates can you determine production of hydrogen sulfide?

1. HE

2. MSA

3. MacConkey

4. XLD

Expert Solution

1. HE is Hektoen enteric medium. It is a selective and differential media for Shigella and Salmonella species. It has a thiosulfate. Thiosulfate reacts with hydrogen sulfide to form a black precipitate. Shigella does not produce H2S and appears as green colonies. Salmonella produces H2S and hence black colonies.

2. MSA stands for Mannitol salt agar. Salt prevents the growth of most gram-positive bacteria. Mannitol is used to check for the fermentation capability of certain bacteria. It does not have any ingredient to detect H2S production.

3. MacConkey agar has crystal violet and bile salts. This prevents the growth of most gram-positive bacteria. It does not have any component to detect the production of H2S.

4. XLD agar or Xylose Lysine Deoxycholate agar is a selective growth medium that is involved in the isolation of Salmonella and Shigella. This medium also has thiosulfate that turns black when Salmonella produces H2S.

Therefore, of the given options, the media that can be used to detect the production of hydrogen sulfide are HE and XLD.

gladiator answered 2 years ago

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