PetriKey

Lab method

Thayer-Martin agar concept

VCN-selective chocolate agar for Neisseria

Gram negativegram-negativeselectiveneisseriachocolate-agarfastidious

High-yield clue

Thayer-Martin (VCN) selectively favors Neisseria gonorrhoeae and N. meningitidis while inhibiting normal flora.

Overview

A selective enriched-chocolate-agar concept with added antimicrobials (vancomycin, colistin, nystatin) that suppress competing flora so fastidious Neisseria can be recovered.

Classification

  • Selective enriched medium concept
  • Chocolate agar base
  • VCN antimicrobial supplement

Lab & identification clues

  • VCN = vancomycin, colistin, nystatin selection
  • Vancomycin suppresses Gram-positives
  • Colistin suppresses other Gram-negatives
  • Nystatin suppresses yeasts/fungi

Associations

  • Neisseria selective isolation vocabulary
  • Chocolate agar enrichment link
  • Fastidious organism study framing

Commonly confused with

  • Chocolate agar (XV factors)
  • MacConkey agar

Your notes

Original concept summary for coursework. Sources checked: OpenStax Microbiology 2e and NCBI Bookshelf Medical Microbiology; reviewed 2026-06. Describes vocabulary and interpretation concepts only; not a lab protocol and not for handling specimens or identifying patient isolates.

OpenStax: Microbiology 2e staining, media, and biochemical-test foundationssourceNCBI Bookshelf: Medical Microbiology diagnostic concept foundationssource