Gold standard for detection of S equi*1 pointColumbia CNA blood agarDirect SmearBacterial isolation with chocolate agarH & E stainNone of the above

The gold standard for detection of Streptococcus equi, often abbreviated as S. equi, is bacterial isolation. However, the medium used is not chocolate agar but rather a selective medium such as Columbia CNA blood agar.

Here's a step-by-step breakdown:

1. Sample Collection: The first step in detecting S. equi is to collect a sample. This is typically done by swabbing the nasopharynx or by aspirating pus from abscesses.

2. Plating on Selective Medium: The sample is then plated on a selective medium, such as Columbia CNA blood agar, which encourages the growth of gram-positive bacteria like S. equi and inhibits the growth of gram-negative bacteria.

3. Incubation: The plate is incubated at a suitable temperature (usually 37 degrees Celsius) for 24-48 hours to allow the bacteria to grow.

4. Identification: After incubation, the colonies of bacteria are identified based on their morphology, hemolytic properties, and other biochemical tests.

5. Confirmation: The identification of S. equi can be confirmed by further tests such as PCR or serological tests.

So, the correct answer to your question would be "Columbia CNA blood agar".