Selective media for N. gonorrhoeael
**Core Concept**
Selective media for Neisseria gonorrhoeae is a type of growth medium that allows the growth of gonococci while inhibiting the growth of other bacteria. This is crucial for the isolation and identification of N. gonorrhoeae from clinical specimens.
**Why the Correct Answer is Right**
The primary selective agent in these media is thionine, which acts as an inhibitor of other bacteria. Thionine inhibits the growth of gram-positive bacteria and many gram-negative bacteria, while allowing the growth of N. gonorrhoeae. This selective action is due to the ability of N. gonorrhoeae to reduce thionine to its colorless form, thereby avoiding its toxic effects.
**Why Each Wrong Option is Incorrect**
**Option A:** Blood agar is a general-purpose medium that supports the growth of many types of bacteria, including those that may contaminate clinical specimens. It is not selective for N. gonorrhoeae.
**Option B:** Chocolate agar is enriched with blood and is used for the growth of Haemophilus species, not N. gonorrhoeae.
**Option C:** MacConkey agar is a selective medium for gram-negative bacteria, but it is not specific for N. gonorrhoeae.
**Clinical Pearl / High-Yield Fact**
Thionine-based selective media are essential for the isolation of N. gonorrhoeae from clinical specimens, as they allow for the differentiation of gonococci from other bacteria that may contaminate the specimen.
**Correct Answer:** C. New York City agar.