There has been an outbreak of food born salmonella gastroenteritis in the community and the stool samples have been received in the laboratory. Which is the enrichment medium of choice?
**Core Concept**
The question is testing the knowledge of enrichment media used for the isolation of Salmonella species from stool samples. Enrichment media are specialized growth media that provide optimal conditions for the growth of specific microorganisms, such as Salmonella, which are often present in small numbers in the environment.
**Why the Correct Answer is Right**
The correct answer is **B. Selenite F broth**. Selenite F broth is a selective and enrichment medium for the isolation of Salmonella species from stool samples. It contains sodium selenite, which inhibits the growth of gram-positive bacteria and other contaminants, allowing Salmonella to grow and multiply. The presence of sodium selenite also helps to select for Salmonella, as it is more resistant to its toxic effects than other bacteria.
**Why Each Wrong Option is Incorrect**
* **Option A:** is incorrect because it does not specify a medium suitable for the enrichment of Salmonella. While it may be a general-purpose medium, it is not selective or enrichment for Salmonella.
* **Option C:** is incorrect because it is a general-purpose medium for the isolation of enteric pathogens, but it is not as selective or effective for Salmonella as Selenite F broth.
* **Option D:** is incorrect because it is a selective medium for the isolation of Staphylococcus aureus, not Salmonella.
**Clinical Pearl / High-Yield Fact**
For the isolation of Salmonella from stool samples, it is essential to use a selective and enrichment medium such as Selenite F broth. This is because Salmonella is often present in small numbers in the environment, and the use of a selective medium helps to eliminate contaminants and allow the growth of Salmonella.
**Correct Answer:** B. Selenite F broth