A/ACit-

Acid/Acid Citrate Negative Group
The bacteria in this group are Escherichia coli and Proteus vulgaris. Hydrogen Sulfide results can seperate them, but PR Sucrose and Lactose can confirm it.

Tests
Essential: PR Sucrose, PR Lactose

Helpful: Earlier Sulfur result

Key
Escherichia coli:  Lactose positive, Sulfide negative

Proteus vulgaris: Lactose negative, Sulfide positive