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

In 1957, Slanetz and Bartley described this improved version of the original medium of Slanetz et al. (1955). The medium relies upon the selective inhibitory properties of sodium azide and the incorporation of tetrazolium, which most organisms growing on this medium will reduce to some extent under the conditions provided. Although devised originally for use with membrane filters, the medium can also be used for direct plating. Selectivity is increased by incubation at 37°C for 4 h followed by 44±1°C for 44 h.