Lab method
Triple sugar iron agar
Slant/butt fermentation + H2S blackening
High-yield clue
A black TSI butt signals H2S production, a classic Salmonella and Proteus study clue.
Overview
A differential medium with glucose, lactose, sucrose, and iron salts read as slant-over-butt color plus gas and hydrogen sulfide to profile enteric Gram-negative fermentation vocabulary.
Classification
- Differential medium concept
- Phenol red pH indicator
- Ferrous sulfate H2S indicator
Lab & identification clues
- Yellow slant/butt (A/A) = lactose or sucrose fermenter
- Red slant, yellow butt (K/A) = glucose-only fermenter
- Black precipitate = H2S positive
- Cracks/bubbles = gas production
Associations
- Salmonella and Proteus H2S vocabulary
- Lactose vs non-lactose fermenter framing
- Enteric Gram-negative profiling
Commonly confused with
- MacConkey agar
- EMB agar concept
Frequently asked questions
What is Triple sugar iron agar?
A differential medium with glucose, lactose, sucrose, and iron salts read as slant-over-butt color plus gas and hydrogen sulfide to profile enteric Gram-negative fermentation vocabulary.
What is the high-yield clue for Triple sugar iron agar?
A black TSI butt signals H2S production, a classic Salmonella and Proteus study clue.
What is Triple sugar iron agar associated with?
Triple sugar iron agar is associated with Salmonella and Proteus H2S vocabulary, Lactose vs non-lactose fermenter framing, and Enteric Gram-negative profiling.
What is Triple sugar iron agar commonly confused with?
Triple sugar iron agar is commonly confused with MacConkey agar and EMB agar concept.
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.