Which agar medium is claimed to ease isolation of Neisseria gonorrhoeae from contaminated specimens?

Which agar medium is claimed to ease isolation of Neisseria gonorrhoeae from contaminated specimens?

• A. MacConkey agar
• B. CIN agar
• C. Mannitol salt agar
• D. Chocolate agar

Answer: (B)

Neisseria gonorrhoeae is a fastidious organism that requires enriched conditions to grow, especially when samples are mixed with other bacteria. The goal is to provide nutrients the bacteria need while limiting competing flora so the gonococcus can form recognizable colonies. Chocolate agar fits this need because it uses lysed red blood cells to release X (hemin) and V (NAD) factors, which Neisseria gonorrhoeae readily utilize. This enrichment helps the organism grow more robustly even in the presence of contaminants, making colonies easier to detect. The other options are less suited for this purpose. MacConkey agar targets Gram-negative enterics and bile salts inhibit non-enteric organisms, so it isn’t ideal for Neisseria. Mannitol salt agar selects for Staphylococcus species due to its high salt content, not gonococcus. CIN agar is designed to isolate Yersinia enterocolitica and contains inhibitors that suppress many organisms; it’s not typically used to recover Neisseria gonorrhoeae. So, among these choices, chocolate agar is the medium that best supports growth of Neisseria gonorrhoeae from contaminated specimens. In practice, selective media with antibiotics (like Thayer-Martin) are used to further suppress flora, but chocolate agar provides the necessary enrichment for gonococci.

Neisseria gonorrhoeae is a fastidious organism that requires enriched conditions to grow, especially when samples are mixed with other bacteria. The goal is to provide nutrients the bacteria need while limiting competing flora so the gonococcus can form recognizable colonies.

Chocolate agar fits this need because it uses lysed red blood cells to release X (hemin) and V (NAD) factors, which Neisseria gonorrhoeae readily utilize. This enrichment helps the organism grow more robustly even in the presence of contaminants, making colonies easier to detect.

The other options are less suited for this purpose. MacConkey agar targets Gram-negative enterics and bile salts inhibit non-enteric organisms, so it isn’t ideal for Neisseria. Mannitol salt agar selects for Staphylococcus species due to its high salt content, not gonococcus. CIN agar is designed to isolate Yersinia enterocolitica and contains inhibitors that suppress many organisms; it’s not typically used to recover Neisseria gonorrhoeae.

So, among these choices, chocolate agar is the medium that best supports growth of Neisseria gonorrhoeae from contaminated specimens. In practice, selective media with antibiotics (like Thayer-Martin) are used to further suppress flora, but chocolate agar provides the necessary enrichment for gonococci.