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

This medium was devised by Evans and Niven (1951) and a modification developed by Shipp (1964) for the rapid non-selective enumeration of bacteria capable of elaborating H₂O₂ during growth under aerobic conditions. Such a reaction on cooked cured meats results in a “green” discoloration. This principle was also used by Whittenbury (1964) and Reuter (1970).

Double layer plates are prepared.

Bottom layer: APT agar (15 mL).

Top layer: 20 g of MnO₂ are added to 200 mL APT broth, dispensed in 10 mL amounts and sterilised by autoclaving at 121°C for 15 min. To each 100 mL amount of sterile, cooled (45°C) APT agar is added 10 mL of MnO₂ suspension. When the bottom layer is firmly set, a thin layer of APT agar with MnO₂ is added.