Lab method
Methyl red / Voges-Proskauer test
MR+ E. coli vs VP+ Klebsiella
High-yield clue
Escherichia coli is MR-positive/VP-negative, whereas Klebsiella and Enterobacter are MR-negative/VP-positive.
Overview
A paired concept from one broth: methyl red detects stable mixed-acid fermentation, while Voges-Proskauer detects the neutral end-product acetoin from the butanediol pathway.
Classification
- Fermentation-pathway concept
- Two reads from MR-VP broth
- Part of IMViC panel
Lab & identification clues
- MR red = mixed-acid fermenter (E. coli)
- VP red = acetoin producer (Klebsiella/Enterobacter)
- Barritt's reagents develop the VP color
- The M and V in IMViC
Associations
- E. coli vs Klebsiella differentiation
- IMViC panel study framing
- Enteric fermentation vocabulary
Commonly confused with
- Indole test
- Citrate utilization test
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.