Bacterium
Escherichia coli
Gram-negative lactose-fermenting rod
ESH-er-IK-ee-uh KOH-lye
High-yield clue
Gram-negative rod + lactose fermenter + oxidase negative is the core lab clue.
Overview
A common Gram-negative enteric rod used to teach lactose fermentation, GI pathotypes, and urinary associations.
Classification
- Gram-negative
- Rod
- Enterobacterales
- Facultative anaerobe
Lab & identification clues
- Lactose fermenter on MacConkey
- Oxidase negative
- Indole positive
Associations
- Urinary tract study association
- GI pathotype vocabulary
- K1 capsule meningitis vocabulary
- Model organism in genetics
Commonly confused with
- Klebsiella pneumoniae
- Salmonella enterica
- Shigella species
Frequently asked questions
What is Escherichia coli?
A common Gram-negative enteric rod used to teach lactose fermentation, GI pathotypes, and urinary associations.
What is the Gram stain of Escherichia coli?
Escherichia coli is Gram negative.
What are the lab clues for Escherichia coli?
Lab clues for Escherichia coli include Lactose fermenter on MacConkey, Oxidase negative, and Indole positive.
What is Escherichia coli commonly confused with?
Escherichia coli is commonly confused with Klebsiella pneumoniae, Salmonella enterica, and Shigella species.
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.