a. Method to inoculate slant: stab and streak procedure which requires insertion of sterile straight needle from the base of the slant into the butt. Upon withdrawal, the slanted surface of the medium is streaked. Determining activities of the organism:
a. Alkaline slant (red) and acid butt (yellow) with or without gas production (breaks in the agar butt): Only glucose fermentation has occurred. Glucose was degraded first. Since this substrate is minimally present, the small amount of acid produced on the slant surface is oxidized rapidly. Peptones in the medium are used in production of alkali. In the butt the acid reaction is maintained because of reduced O2 tension and slower growth of the organism.
b.Acid slant (yellow) and acid butt (yellow) with or without gas production: Lactose and or sucrose fermentation has occurred. Since these substances are present in higher concentrations, they serve as the substrates for continued fermentative activities with maintenance of an acid reaction in both slant and butt.
c.Alkaline slant (red) and alkaline butt (red) or no change (orange-red) butt- No carbohydrate fermentation has occurred. Instead peptones are catabolized under anaerobic and or aerobic conditions resulting in an alkaline pH due to production of ammonia. If only aerobic degradation of peptones occur, the alkaline reaction is evidenced only on the slant surface. If there is aerobic and anaerobic utilization of peptone, the alkaline reaction is present on the slant and the butt.