This monograph has been assessed by members of the IUMS–ICFMH Working Party on Culture Media and given ‘Approved’ status.

This medium was devised by Mossel et al. (1967) for the isolation of Bacillus cereus. It relies on the selective inhibitory component polymyxin and two indicator systems, mannitol and phenol red and egg yolk. Thus growth of many unwanted organisms is suppressed. Bacillus cereus does not attack mannitol but dissimilates egg yolk and consequently gives rise to typical bacilliform colonies with purple-red zones and white haloes. Bacillus anthracis, Bacillus mycoides, Bacillus pseudomycoides, Bacillus thuringiensis and Bacillus weihenstephanensis may not be distinguishable from Bacillus cereus.