Lab method
Citrate utilization test
Prussian blue = citrate positive (Klebsiella)
SIT-rate
High-yield clue
Simmons citrate turning Prussian blue means citrate-positive (Klebsiella, Enterobacter), while Escherichia coli stays green (negative).
Overview
A biochemical concept testing whether an organism can use citrate as its sole carbon source on Simmons citrate, raising pH and turning the indicator blue.
Classification
- Carbon-source utilization concept
- Simmons citrate medium
- Bromothymol blue pH readout
Lab & identification clues
- Green to Prussian blue = citrate positive
- E. coli is citrate negative (stays green)
- Klebsiella and Enterobacter are citrate positive
- The C in the IMViC panel
Associations
- E. coli vs Klebsiella differentiation
- IMViC panel study framing
- Enteric Gram-negative identification
Commonly confused with
- Indole test
- Methyl red / Voges-Proskauer 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.