Thayer-Martin agar is selective for which organisms?

Thayer-Martin agar is selective for which organisms?

• A. Neisseria gonorrhoeae and Neisseria meningitidis
• B. Escherichia coli
• C. Streptococcus pneumoniae
• D. Pseudomonas aeruginosa

Answer: (A)

Thayer-Martin agar is a selective medium designed to isolate Neisseria species, especially pathogenic Neisseria gonorrhoeae and Neisseria meningitidis. It achieves this by including antibiotics in the agar that suppress most competing flora: vancomycin blocks Gram-positive growth, colistin inhibits many Gram-negative bacteria, and nystatin prevents fungal contamination. The base is enriched (often chocolate agar) to provide the growth factors Neisseria require, but the antibiotic mix makes it unlikely for other organisms in mixed clinical specimens to grow. That’s why organisms like Escherichia coli, Streptococcus pneumoniae, or Pseudomonas aeruginosa typically won’t grow on this medium. In short, Thayer-Martin agar selectively supports Neisseria while inhibiting others, enabling reliable isolation of gonorrhea and meningitis-causing Neisseria from samples.

Thayer-Martin agar is a selective medium designed to isolate Neisseria species, especially pathogenic Neisseria gonorrhoeae and Neisseria meningitidis. It achieves this by including antibiotics in the agar that suppress most competing flora: vancomycin blocks Gram-positive growth, colistin inhibits many Gram-negative bacteria, and nystatin prevents fungal contamination. The base is enriched (often chocolate agar) to provide the growth factors Neisseria require, but the antibiotic mix makes it unlikely for other organisms in mixed clinical specimens to grow. That’s why organisms like Escherichia coli, Streptococcus pneumoniae, or Pseudomonas aeruginosa typically won’t grow on this medium. In short, Thayer-Martin agar selectively supports Neisseria while inhibiting others, enabling reliable isolation of gonorrhea and meningitis-causing Neisseria from samples.