What type of slant and butt reaction do nonfermenters show in TSIA?

Nonfermenters typically show an alkaline slant and an alkaline butt reaction in Triple Sugar Iron Agar (TSIA) tests. This is because nonfermenters do not utilize the sugars present in TSIA, which are glucose, lactose, and sucrose, for fermentation. As a result, they do not produce acid, which is detected by the change in color of the medium.

The alkaline slant occurs as the nitrogen sources are utilized, leading to the production of ammonia, which raises the pH and results in the alkaline reaction. Since no acid is produced in the butt either, it remains alkaline as well. This dual alkaline reaction is characteristic of nonfermenters, setting them apart from fermenters, which utilize the available sugars and produce acid, leading to acidic reactions in either or both the slant and the butt.