MacConkey Agar without Salt has the same formulation as MacConkey Agar except that it does not contain added salt and, therefore, provides a ‘low electrolyte medium’ on which most Proteus species do not spread. The medium has found particular favor for use in the examination of urine samples so that overgrowth of other organisms is prevented.

Precautions:
The colonial characteristics described give presumptive identification only of the isolated organisms. It is necessary to subculture and carry out confirmation tests for final identification.
To enhance the pigment of suspected Staphylococcus aureus, hold the plates on the bench at ambient temperature for 12-18 hours.
This medium may produce a discrete precipitate on cold storage of 2 - 10°C. This in no way affects the performance of the medium.