Selective media for Salmonella isolation: Which of the following culture media is specifically selective for Salmonella, aiding in primary isolation from clinical or food specimens?

Introduction / Context:Appropriate selective media increase the likelihood of recovering Salmonella from mixed flora. Different media are tailored to different genera, so choosing correctly prevents false negatives and saves lab time.

Given Data / Assumptions:

• We compare three named media.
• Goal: selection for Salmonella during isolation.
• Standard formulations and uses are assumed.

Concept / Approach:Bismuth sulphite agar (Wilson and Blair's medium) is a selective medium specifically designed for Salmonella (notably S. Typhi), incorporating brilliant green, bismuth sulphite, and other inhibitors that suppress competing flora while allowing characteristic black colonies due to H2S production. In contrast, TCBS (thiosulfate-citrate-bile salts-sucrose) is selective for Vibrio species, and generic bile salt agar selects for enterics but is not specifically tailored to Salmonella over other Enterobacteriaceae.

Step-by-Step Solution:Identify which listed medium targets Salmonella: Wilson and Blair's bismuth sulphite agar.Recognize TCBS selectively isolates Vibrio, not Salmonella.Acknowledge bile salt agar as broadly selective but not specific for Salmonella.Choose the medium explicitly formulated for Salmonella.

Verification / Alternative check:Diagnostic manuals recommend bismuth sulphite agar or other Salmonella-selective media (e.g., XLD, HE) rather than TCBS when Salmonella is suspected.

Why Other Options Are Wrong:

• TCBS: optimized for Vibrio cholerae/parahaemolyticus recovery.
• Bile salt agar: lacks the specificity for Salmonella.
• All of the above: incorrect because media differ in target organisms.

Common Pitfalls:Using TCBS for suspected Salmonella will miss isolates; always match medium to suspected pathogen.

Final Answer:Wilson and Blair's brilliant-green bismuth sulphite agar medium