Lab method
EMB agar concept
Green metallic sheen = E. coli
High-yield clue
A green metallic sheen on EMB is the classic clue for strong lactose fermentation by Escherichia coli.
Overview
Eosin methylene blue is a selective and differential medium concept that inhibits Gram-positives and distinguishes lactose fermenters by colony color and sheen.
Classification
- Selective and differential medium
- Inhibits Gram-positive growth
- Eosin/methylene blue indicators
Lab & identification clues
- Green metallic sheen = vigorous lactose fermenter (E. coli)
- Dark/purple colonies = slower fermenters (Klebsiella)
- Colorless colonies = non-lactose fermenters
- Dyes suppress Gram-positive organisms
Associations
- E. coli sheen study clue
- Lactose vs non-lactose fermenter framing
- Enteric Gram-negative differentiation
Commonly confused with
- MacConkey agar
- TSI 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.